@chapter Filtering Introduction @c man begin FILTERING INTRODUCTION Filtering in FFmpeg is enabled through the libavfilter library. Libavfilter is the filtering API of FFmpeg. It is the substitute of the now deprecated 'vhooks' and started as a Google Summer of Code project. Audio filtering integration into the main FFmpeg repository is a work in progress, so audio API and ABI should not be considered stable yet. In libavfilter, it is possible for filters to have multiple inputs and multiple outputs. To illustrate the sorts of things that are possible, we can use a complex filter graph. For example, the following one: @example input --> split --> fifo -----------------------> overlay --> output | ^ | | +------> fifo --> crop --> vflip --------+ @end example splits the stream in two streams, sends one stream through the crop filter and the vflip filter before merging it back with the other stream by overlaying it on top. You can use the following command to achieve this: @example ffmpeg -i input -vf "[in] split [T1], fifo, [T2] overlay=0:H/2 [out]; [T1] fifo, crop=iw:ih/2:0:ih/2, vflip [T2]" output @end example The result will be that in output the top half of the video is mirrored onto the bottom half. Filters are loaded using the @var{-vf} or @var{-af} option passed to @command{ffmpeg} or to @command{ffplay}. Filters in the same linear chain are separated by commas. In our example, @var{split, fifo, overlay} are in one linear chain, and @var{fifo, crop, vflip} are in another. The points where the linear chains join are labeled by names enclosed in square brackets. In our example, that is @var{[T1]} and @var{[T2]}. The special labels @var{[in]} and @var{[out]} are the points where video is input and output. Some filters take in input a list of parameters: they are specified after the filter name and an equal sign, and are separated from each other by a colon. There exist so-called @var{source filters} that do not have an audio/video input, and @var{sink filters} that will not have audio/video output. @c man end FILTERING INTRODUCTION @chapter graph2dot @c man begin GRAPH2DOT The @file{graph2dot} program included in the FFmpeg @file{tools} directory can be used to parse a filter graph description and issue a corresponding textual representation in the dot language. Invoke the command: @example graph2dot -h @end example to see how to use @file{graph2dot}. You can then pass the dot description to the @file{dot} program (from the graphviz suite of programs) and obtain a graphical representation of the filter graph. For example the sequence of commands: @example echo @var{GRAPH_DESCRIPTION} | \ tools/graph2dot -o graph.tmp && \ dot -Tpng graph.tmp -o graph.png && \ display graph.png @end example can be used to create and display an image representing the graph described by the @var{GRAPH_DESCRIPTION} string. Note that this string must be a complete self-contained graph, with its inputs and outputs explicitly defined. For example if your command line is of the form: @example ffmpeg -i infile -vf scale=640:360 outfile @end example your @var{GRAPH_DESCRIPTION} string will need to be of the form: @example nullsrc,scale=640:360,nullsink @end example you may also need to set the @var{nullsrc} parameters and add a @var{format} filter in order to simulate a specific input file. @c man end GRAPH2DOT @chapter Filtergraph description @c man begin FILTERGRAPH DESCRIPTION A filtergraph is a directed graph of connected filters. It can contain cycles, and there can be multiple links between a pair of filters. Each link has one input pad on one side connecting it to one filter from which it takes its input, and one output pad on the other side connecting it to the one filter accepting its output. Each filter in a filtergraph is an instance of a filter class registered in the application, which defines the features and the number of input and output pads of the filter. A filter with no input pads is called a "source", a filter with no output pads is called a "sink". @anchor{Filtergraph syntax} @section Filtergraph syntax A filtergraph can be represented using a textual representation, which is recognized by the @option{-filter}/@option{-vf} and @option{-filter_complex} options in @command{ffmpeg} and @option{-vf} in @command{ffplay}, and by the @code{avfilter_graph_parse()}/@code{avfilter_graph_parse2()} function defined in @file{libavfilter/avfiltergraph.h}. A filterchain consists of a sequence of connected filters, each one connected to the previous one in the sequence. A filterchain is represented by a list of ","-separated filter descriptions. A filtergraph consists of a sequence of filterchains. A sequence of filterchains is represented by a list of ";"-separated filterchain descriptions. A filter is represented by a string of the form: [@var{in_link_1}]...[@var{in_link_N}]@var{filter_name}=@var{arguments}[@var{out_link_1}]...[@var{out_link_M}] @var{filter_name} is the name of the filter class of which the described filter is an instance of, and has to be the name of one of the filter classes registered in the program. The name of the filter class is optionally followed by a string "=@var{arguments}". @var{arguments} is a string which contains the parameters used to initialize the filter instance, and are described in the filter descriptions below. The list of arguments can be quoted using the character "'" as initial and ending mark, and the character '\' for escaping the characters within the quoted text; otherwise the argument string is considered terminated when the next special character (belonging to the set "[]=;,") is encountered. The name and arguments of the filter are optionally preceded and followed by a list of link labels. A link label allows to name a link and associate it to a filter output or input pad. The preceding labels @var{in_link_1} ... @var{in_link_N}, are associated to the filter input pads, the following labels @var{out_link_1} ... @var{out_link_M}, are associated to the output pads. When two link labels with the same name are found in the filtergraph, a link between the corresponding input and output pad is created. If an output pad is not labelled, it is linked by default to the first unlabelled input pad of the next filter in the filterchain. For example in the filterchain: @example nullsrc, split[L1], [L2]overlay, nullsink @end example the split filter instance has two output pads, and the overlay filter instance two input pads. The first output pad of split is labelled "L1", the first input pad of overlay is labelled "L2", and the second output pad of split is linked to the second input pad of overlay, which are both unlabelled. In a complete filterchain all the unlabelled filter input and output pads must be connected. A filtergraph is considered valid if all the filter input and output pads of all the filterchains are connected. Libavfilter will automatically insert scale filters where format conversion is required. It is possible to specify swscale flags for those automatically inserted scalers by prepending @code{sws_flags=@var{flags};} to the filtergraph description. Follows a BNF description for the filtergraph syntax: @example @var{NAME} ::= sequence of alphanumeric characters and '_' @var{LINKLABEL} ::= "[" @var{NAME} "]" @var{LINKLABELS} ::= @var{LINKLABEL} [@var{LINKLABELS}] @var{FILTER_ARGUMENTS} ::= sequence of chars (eventually quoted) @var{FILTER} ::= [@var{LINKNAMES}] @var{NAME} ["=" @var{ARGUMENTS}] [@var{LINKNAMES}] @var{FILTERCHAIN} ::= @var{FILTER} [,@var{FILTERCHAIN}] @var{FILTERGRAPH} ::= [sws_flags=@var{flags};] @var{FILTERCHAIN} [;@var{FILTERGRAPH}] @end example @section Notes on filtergraph escaping Some filter arguments require the use of special characters, typically @code{:} to separate key=value pairs in a named options list. In this case the user should perform a first level escaping when specifying the filter arguments. For example, consider the following literal string to be embedded in the @ref{drawtext} filter arguments: @example this is a 'string': may contain one, or more, special characters @end example Since @code{:} is special for the filter arguments syntax, it needs to be escaped, so you get: @example text=this is a \'string\'\: may contain one, or more, special characters @end example A second level of escaping is required when embedding the filter arguments in a filtergraph description, in order to escape all the filtergraph special characters. Thus the example above becomes: @example drawtext=text=this is a \\\'string\\\'\\: may contain one\, or more\, special characters @end example Finally an additional level of escaping may be needed when writing the filtergraph description in a shell command, which depends on the escaping rules of the adopted shell. For example, assuming that @code{\} is special and needs to be escaped with another @code{\}, the previous string will finally result in: @example -vf "drawtext=text=this is a \\\\\\'string\\\\\\'\\\\: may contain one\\, or more\\, special characters" @end example Sometimes, it might be more convenient to employ quoting in place of escaping. For example the string: @example Caesar: tu quoque, Brute, fili mi @end example Can be quoted in the filter arguments as: @example text='Caesar: tu quoque, Brute, fili mi' @end example And finally inserted in a filtergraph like: @example drawtext=text=\'Caesar: tu quoque\, Brute\, fili mi\' @end example See the @ref{quoting_and_escaping, Quoting and escaping} section for more information about the escaping and quoting rules adopted by FFmpeg. @c man end FILTERGRAPH DESCRIPTION @chapter Audio Filters @c man begin AUDIO FILTERS When you configure your FFmpeg build, you can disable any of the existing filters using @code{--disable-filters}. The configure output will show the audio filters included in your build. Below is a description of the currently available audio filters. @section aconvert Convert the input audio format to the specified formats. The filter accepts a string of the form: "@var{sample_format}:@var{channel_layout}". @var{sample_format} specifies the sample format, and can be a string or the corresponding numeric value defined in @file{libavutil/samplefmt.h}. Use 'p' suffix for a planar sample format. @var{channel_layout} specifies the channel layout, and can be a string or the corresponding number value defined in @file{libavutil/channel_layout.h}. The special parameter "auto", signifies that the filter will automatically select the output format depending on the output filter. Some examples follow. @itemize @item Convert input to float, planar, stereo: @example aconvert=fltp:stereo @end example @item Convert input to unsigned 8-bit, automatically select out channel layout: @example aconvert=u8:auto @end example @end itemize @section aformat Convert the input audio to one of the specified formats. The framework will negotiate the most appropriate format to minimize conversions. The filter accepts the following named parameters: @table @option @item sample_fmts A comma-separated list of requested sample formats. @item sample_rates A comma-separated list of requested sample rates. @item channel_layouts A comma-separated list of requested channel layouts. @end table If a parameter is omitted, all values are allowed. For example to force the output to either unsigned 8-bit or signed 16-bit stereo: @example aformat=sample_fmts\=u8\,s16:channel_layouts\=stereo @end example @section amerge Merge two or more audio streams into a single multi-channel stream. The filter accepts the following named options: @table @option @item inputs Set the number of inputs. Default is 2. @end table If the channel layouts of the inputs are disjoint, and therefore compatible, the channel layout of the output will be set accordingly and the channels will be reordered as necessary. If the channel layouts of the inputs are not disjoint, the output will have all the channels of the first input then all the channels of the second input, in that order, and the channel layout of the output will be the default value corresponding to the total number of channels. For example, if the first input is in 2.1 (FL+FR+LF) and the second input is FC+BL+BR, then the output will be in 5.1, with the channels in the following order: a1, a2, b1, a3, b2, b3 (a1 is the first channel of the first input, b1 is the first channel of the second input). On the other hand, if both input are in stereo, the output channels will be in the default order: a1, a2, b1, b2, and the channel layout will be arbitrarily set to 4.0, which may or may not be the expected value. All inputs must have the same sample rate, and format. If inputs do not have the same duration, the output will stop with the shortest. Example: merge two mono files into a stereo stream: @example amovie=left.wav [l] ; amovie=right.mp3 [r] ; [l] [r] amerge @end example Example: multiple merges: @example ffmpeg -f lavfi -i " amovie=input.mkv:si=0 [a0]; amovie=input.mkv:si=1 [a1]; amovie=input.mkv:si=2 [a2]; amovie=input.mkv:si=3 [a3]; amovie=input.mkv:si=4 [a4]; amovie=input.mkv:si=5 [a5]; [a0][a1][a2][a3][a4][a5] amerge=inputs=6" -c:a pcm_s16le output.mkv @end example @section amix Mixes multiple audio inputs into a single output. For example @example ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex amix=inputs=3:duration=first:dropout_transition=3 OUTPUT @end example will mix 3 input audio streams to a single output with the same duration as the first input and a dropout transition time of 3 seconds. The filter accepts the following named parameters: @table @option @item inputs Number of inputs. If unspecified, it defaults to 2. @item duration How to determine the end-of-stream. @table @option @item longest Duration of longest input. (default) @item shortest Duration of shortest input. @item first Duration of first input. @end table @item dropout_transition Transition time, in seconds, for volume renormalization when an input stream ends. The default value is 2 seconds. @end table @section anull Pass the audio source unchanged to the output. @section aresample Resample the input audio to the specified parameters. If none are specified then the filter will automatically convert between its input and output. This filter is also able to stretch/squeeze the audio data to make it match the timestamps or to inject silence / cut out audio to make it match the timestamps, do a combination of both or do neither. The filter accepts the following named parameters: @table @option @item min_comp Minimum difference between timestamps and audio data (in seconds) to trigger stretching/squeezing/filling or trimming of the data to make it match the timestamps. The default is that stretching/squeezing/filling and trimming is disabled (min_comp = infinite). @item min_hard_comp Minimum difference between timestamps and audio data (in seconds) to trigger adding/dropping samples to make it match the timestamps. This option effectively is a threshold to select between hard (trim/fill) and soft (squeeze/stretch) compensation. Note that all compensation is by default disabled through min_comp. The default is 0.1 seconds. @item max_soft_comp Maximum stretch/squeeze factor. Default value 0. @item tsf, internal_sample_fmt Internal sampling format. Default is automatic selection @item clev, center_mix_level center mix level, for rematrixing Default is 3.0dB @item slev, surround_mix_level surround mix level, for rematrixing Default is 3.0dB @item rmvol, rematrix_volume rematrix volume Default is 1.0 @item lfe_mix_level Low frequency effects mix level. Default is 0 @item matrix_encoding matrixed stereo encoding @table @option @item none No matrixed stereo encoding @item dolby Dolby matrixed stereo encoding @item dolby Dolby Pro Logic II matrixed stereo encoding @end table Default value is @code{none}. @end table For example, to resample the input audio to 44100Hz: @example aresample=44100 @end example @section asetnsamples Set the number of samples per each output audio frame. The last output packet may contain a different number of samples, as the filter will flush all the remaining samples when the input audio signal its end. The filter accepts parameters as a list of @var{key}=@var{value} pairs, separated by ":". @table @option @item nb_out_samples, n Set the number of frames per each output audio frame. The number is intended as the number of samples @emph{per each channel}. Default value is 1024. @item pad, p If set to 1, the filter will pad the last audio frame with zeroes, so that the last frame will contain the same number of samples as the previous ones. Default value is 1. @end table For example, to set the number of per-frame samples to 1234 and disable padding for the last frame, use: @example asetnsamples=n=1234:p=0 @end example @section ashowinfo Show a line containing various information for each input audio frame. The input audio is not modified. The shown line contains a sequence of key/value pairs of the form @var{key}:@var{value}. A description of each shown parameter follows: @table @option @item n sequential number of the input frame, starting from 0 @item pts Presentation timestamp of the input frame, in time base units; the time base depends on the filter input pad, and is usually 1/@var{sample_rate}. @item pts_time presentation timestamp of the input frame in seconds @item pos position of the frame in the input stream, -1 if this information in unavailable and/or meaningless (for example in case of synthetic audio) @item fmt sample format @item chlayout channel layout @item rate sample rate for the audio frame @item nb_samples number of samples (per channel) in the frame @item checksum Adler-32 checksum (printed in hexadecimal) of the audio data. For planar audio the data is treated as if all the planes were concatenated. @item plane_checksums A list of Adler-32 checksums for each data plane. @end table @section asplit Split input audio into several identical outputs. The filter accepts a single parameter which specifies the number of outputs. If unspecified, it defaults to 2. For example: @example [in] asplit [out0][out1] @end example will create two separate outputs from the same input. To create 3 or more outputs, you need to specify the number of outputs, like in: @example [in] asplit=3 [out0][out1][out2] @end example @example ffmpeg -i INPUT -filter_complex asplit=5 OUTPUT @end example will create 5 copies of the input audio. @section astreamsync Forward two audio streams and control the order the buffers are forwarded. The argument to the filter is an expression deciding which stream should be forwarded next: if the result is negative, the first stream is forwarded; if the result is positive or zero, the second stream is forwarded. It can use the following variables: @table @var @item b1 b2 number of buffers forwarded so far on each stream @item s1 s2 number of samples forwarded so far on each stream @item t1 t2 current timestamp of each stream @end table The default value is @code{t1-t2}, which means to always forward the stream that has a smaller timestamp. Example: stress-test @code{amerge} by randomly sending buffers on the wrong input, while avoiding too much of a desynchronization: @example amovie=file.ogg [a] ; amovie=file.mp3 [b] ; [a] [b] astreamsync=(2*random(1))-1+tanh(5*(t1-t2)) [a2] [b2] ; [a2] [b2] amerge @end example @section atempo Adjust audio tempo. The filter accepts exactly one parameter, the audio tempo. If not specified then the filter will assume nominal 1.0 tempo. Tempo must be in the [0.5, 2.0] range. For example, to slow down audio to 80% tempo: @example atempo=0.8 @end example For example, to speed up audio to 125% tempo: @example atempo=1.25 @end example @section earwax Make audio easier to listen to on headphones. This filter adds `cues' to 44.1kHz stereo (i.e. audio CD format) audio so that when listened to on headphones the stereo image is moved from inside your head (standard for headphones) to outside and in front of the listener (standard for speakers). Ported from SoX. @section pan Mix channels with specific gain levels. The filter accepts the output channel layout followed by a set of channels definitions. This filter is also designed to remap efficiently the channels of an audio stream. The filter accepts parameters of the form: "@var{l}:@var{outdef}:@var{outdef}:..." @table @option @item l output channel layout or number of channels @item outdef output channel specification, of the form: "@var{out_name}=[@var{gain}*]@var{in_name}[+[@var{gain}*]@var{in_name}...]" @item out_name output channel to define, either a channel name (FL, FR, etc.) or a channel number (c0, c1, etc.) @item gain multiplicative coefficient for the channel, 1 leaving the volume unchanged @item in_name input channel to use, see out_name for details; it is not possible to mix named and numbered input channels @end table If the `=' in a channel specification is replaced by `<', then the gains for that specification will be renormalized so that the total is 1, thus avoiding clipping noise. @subsection Mixing examples For example, if you want to down-mix from stereo to mono, but with a bigger factor for the left channel: @example pan=1:c0=0.9*c0+0.1*c1 @end example A customized down-mix to stereo that works automatically for 3-, 4-, 5- and 7-channels surround: @example pan=stereo: FL < FL + 0.5*FC + 0.6*BL + 0.6*SL : FR < FR + 0.5*FC + 0.6*BR + 0.6*SR @end example Note that @command{ffmpeg} integrates a default down-mix (and up-mix) system that should be preferred (see "-ac" option) unless you have very specific needs. @subsection Remapping examples The channel remapping will be effective if, and only if: @itemize @item gain coefficients are zeroes or ones, @item only one input per channel output, @end itemize If all these conditions are satisfied, the filter will notify the user ("Pure channel mapping detected"), and use an optimized and lossless method to do the remapping. For example, if you have a 5.1 source and want a stereo audio stream by dropping the extra channels: @example pan="stereo: c0=FL : c1=FR" @end example Given the same source, you can also switch front left and front right channels and keep the input channel layout: @example pan="5.1: c0=c1 : c1=c0 : c2=c2 : c3=c3 : c4=c4 : c5=c5" @end example If the input is a stereo audio stream, you can mute the front left channel (and still keep the stereo channel layout) with: @example pan="stereo:c1=c1" @end example Still with a stereo audio stream input, you can copy the right channel in both front left and right: @example pan="stereo: c0=FR : c1=FR" @end example @section silencedetect Detect silence in an audio stream. This filter logs a message when it detects that the input audio volume is less or equal to a noise tolerance value for a duration greater or equal to the minimum detected noise duration. The printed times and duration are expressed in seconds. @table @option @item duration, d Set silence duration until notification (default is 2 seconds). @item noise, n Set noise tolerance. Can be specified in dB (in case "dB" is appended to the specified value) or amplitude ratio. Default is -60dB, or 0.001. @end table Detect 5 seconds of silence with -50dB noise tolerance: @example silencedetect=n=-50dB:d=5 @end example Complete example with @command{ffmpeg} to detect silence with 0.0001 noise tolerance in @file{silence.mp3}: @example ffmpeg -f lavfi -i amovie=silence.mp3,silencedetect=noise=0.0001 -f null - @end example @section asyncts Synchronize audio data with timestamps by squeezing/stretching it and/or dropping samples/adding silence when needed. The filter accepts the following named parameters: @table @option @item compensate Enable stretching/squeezing the data to make it match the timestamps. Disabled by default. When disabled, time gaps are covered with silence. @item min_delta Minimum difference between timestamps and audio data (in seconds) to trigger adding/dropping samples. Default value is 0.1. If you get non-perfect sync with this filter, try setting this parameter to 0. @item max_comp Maximum compensation in samples per second. Relevant only with compensate=1. Default value 500. @item first_pts Assume the first pts should be this value. The time base is 1 / sample rate. This allows for padding/trimming at the start of stream. By default, no assumption is made about the first frame's expected pts, so no padding or trimming is done. For example, this could be set to 0 to pad the beginning with silence if an audio stream starts after the video stream or to trim any samples with a negative pts due to encoder delay. @end table @section channelsplit Split each channel in input audio stream into a separate output stream. This filter accepts the following named parameters: @table @option @item channel_layout Channel layout of the input stream. Default is "stereo". @end table For example, assuming a stereo input MP3 file @example ffmpeg -i in.mp3 -filter_complex channelsplit out.mkv @end example will create an output Matroska file with two audio streams, one containing only the left channel and the other the right channel. To split a 5.1 WAV file into per-channel files @example ffmpeg -i in.wav -filter_complex 'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]' -map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]' front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]' side_right.wav @end example @section channelmap Remap input channels to new locations. This filter accepts the following named parameters: @table @option @item channel_layout Channel layout of the output stream. @item map Map channels from input to output. The argument is a comma-separated list of mappings, each in the @code{@var{in_channel}-@var{out_channel}} or @var{in_channel} form. @var{in_channel} can be either the name of the input channel (e.g. FL for front left) or its index in the input channel layout. @var{out_channel} is the name of the output channel or its index in the output channel layout. If @var{out_channel} is not given then it is implicitly an index, starting with zero and increasing by one for each mapping. @end table If no mapping is present, the filter will implicitly map input channels to output channels preserving index. For example, assuming a 5.1+downmix input MOV file @example ffmpeg -i in.mov -filter 'channelmap=map=DL-FL\,DR-FR' out.wav @end example will create an output WAV file tagged as stereo from the downmix channels of the input. To fix a 5.1 WAV improperly encoded in AAC's native channel order @example ffmpeg -i in.wav -filter 'channelmap=1\,2\,0\,5\,3\,4:channel_layout=5.1' out.wav @end example @section join Join multiple input streams into one multi-channel stream. The filter accepts the following named parameters: @table @option @item inputs Number of input streams. Defaults to 2. @item channel_layout Desired output channel layout. Defaults to stereo. @item map Map channels from inputs to output. The argument is a comma-separated list of mappings, each in the @code{@var{input_idx}.@var{in_channel}-@var{out_channel}} form. @var{input_idx} is the 0-based index of the input stream. @var{in_channel} can be either the name of the input channel (e.g. FL for front left) or its index in the specified input stream. @var{out_channel} is the name of the output channel. @end table The filter will attempt to guess the mappings when those are not specified explicitly. It does so by first trying to find an unused matching input channel and if that fails it picks the first unused input channel. E.g. to join 3 inputs (with properly set channel layouts) @example ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex join=inputs=3 OUTPUT @end example To build a 5.1 output from 6 single-channel streams: @example ffmpeg -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex 'join=inputs=6:channel_layout=5.1:map=0.0-FL\,1.0-FR\,2.0-FC\,3.0-SL\,4.0-SR\,5.0-LFE' out @end example @section resample Convert the audio sample format, sample rate and channel layout. This filter is not meant to be used directly. @section volume Adjust the input audio volume. The filter accepts the following named parameters. If the key of the first options is omitted, the arguments are interpreted according to the following syntax: @example volume=@var{volume}:@var{precision} @end example @table @option @item volume Expresses how the audio volume will be increased or decreased. Output values are clipped to the maximum value. The output audio volume is given by the relation: @example @var{output_volume} = @var{volume} * @var{input_volume} @end example Default value for @var{volume} is 1.0. @item precision Set the mathematical precision. This determines which input sample formats will be allowed, which affects the precision of the volume scaling. @table @option @item fixed 8-bit fixed-point; limits input sample format to U8, S16, and S32. @item float 32-bit floating-point; limits input sample format to FLT. (default) @item double 64-bit floating-point; limits input sample format to DBL. @end table @end table @subsection Examples @itemize @item Halve the input audio volume: @example volume=volume=0.5 volume=volume=1/2 volume=volume=-6.0206dB @end example In all the above example the named key for @option{volume} can be omitted, for example like in: @example volume=0.5 @end example @item Increase input audio power by 6 decibels using fixed-point precision: @example volume=volume=6dB:precision=fixed @end example @end itemize @section volumedetect Detect the volume of the input video. The filter has no parameters. The input is not modified. Statistics about the volume will be printed in the log when the input stream end is reached. In particular it will show the mean volume (root mean square), maximum volume (on a per-sample basis), and the beginning of an histogram of the registered volume values (from the maximum value to a cumulated 1/1000 of the samples). All volumes are in decibels relative to the maximum PCM value. Here is an excerpt of the output: @example [Parsed_volumedetect_0 @ 0xa23120] mean_volume: -27 dB [Parsed_volumedetect_0 @ 0xa23120] max_volume: -4 dB [Parsed_volumedetect_0 @ 0xa23120] histogram_4db: 6 [Parsed_volumedetect_0 @ 0xa23120] histogram_5db: 62 [Parsed_volumedetect_0 @ 0xa23120] histogram_6db: 286 [Parsed_volumedetect_0 @ 0xa23120] histogram_7db: 1042 [Parsed_volumedetect_0 @ 0xa23120] histogram_8db: 2551 [Parsed_volumedetect_0 @ 0xa23120] histogram_9db: 4609 [Parsed_volumedetect_0 @ 0xa23120] histogram_10db: 8409 @end example It means that: @itemize @item The mean square energy is approximately -27 dB, or 10^-2.7. @item The largest sample is at -4 dB, or more precisely between -4 dB and -5 dB. @item There are 6 samples at -4 dB, 62 at -5 dB, 286 at -6 dB, etc. @end itemize In other words, raising the volume by +4 dB does not cause any clipping, raising it by +5 dB causes clipping for 6 samples, etc. @c man end AUDIO FILTERS @chapter Audio Sources @c man begin AUDIO SOURCES Below is a description of the currently available audio sources. @section abuffer Buffer audio frames, and make them available to the filter chain. This source is mainly intended for a programmatic use, in particular through the interface defined in @file{libavfilter/asrc_abuffer.h}. It accepts the following mandatory parameters: @var{sample_rate}:@var{sample_fmt}:@var{channel_layout} @table @option @item sample_rate The sample rate of the incoming audio buffers. @item sample_fmt The sample format of the incoming audio buffers. Either a sample format name or its corresponging integer representation from the enum AVSampleFormat in @file{libavutil/samplefmt.h} @item channel_layout The channel layout of the incoming audio buffers. Either a channel layout name from channel_layout_map in @file{libavutil/channel_layout.c} or its corresponding integer representation from the AV_CH_LAYOUT_* macros in @file{libavutil/channel_layout.h} @end table For example: @example abuffer=44100:s16p:stereo @end example will instruct the source to accept planar 16bit signed stereo at 44100Hz. Since the sample format with name "s16p" corresponds to the number 6 and the "stereo" channel layout corresponds to the value 0x3, this is equivalent to: @example abuffer=44100:6:0x3 @end example @section aevalsrc Generate an audio signal specified by an expression. This source accepts in input one or more expressions (one for each channel), which are evaluated and used to generate a corresponding audio signal. It accepts the syntax: @var{exprs}[::@var{options}]. @var{exprs} is a list of expressions separated by ":", one for each separate channel. In case the @var{channel_layout} is not specified, the selected channel layout depends on the number of provided expressions. @var{options} is an optional sequence of @var{key}=@var{value} pairs, separated by ":". The description of the accepted options follows. @table @option @item channel_layout, c Set the channel layout. The number of channels in the specified layout must be equal to the number of specified expressions. @item duration, d Set the minimum duration of the sourced audio. See the function @code{av_parse_time()} for the accepted format. Note that the resulting duration may be greater than the specified duration, as the generated audio is always cut at the end of a complete frame. If not specified, or the expressed duration is negative, the audio is supposed to be generated forever. @item nb_samples, n Set the number of samples per channel per each output frame, default to 1024. @item sample_rate, s Specify the sample rate, default to 44100. @end table Each expression in @var{exprs} can contain the following constants: @table @option @item n number of the evaluated sample, starting from 0 @item t time of the evaluated sample expressed in seconds, starting from 0 @item s sample rate @end table @subsection Examples @itemize @item Generate silence: @example aevalsrc=0 @end example @item Generate a sin signal with frequency of 440 Hz, set sample rate to 8000 Hz: @example aevalsrc="sin(440*2*PI*t)::s=8000" @end example @item Generate a two channels signal, specify the channel layout (Front Center + Back Center) explicitly: @example aevalsrc="sin(420*2*PI*t):cos(430*2*PI*t)::c=FC|BC" @end example @item Generate white noise: @example aevalsrc="-2+random(0)" @end example @item Generate an amplitude modulated signal: @example aevalsrc="sin(10*2*PI*t)*sin(880*2*PI*t)" @end example @item Generate 2.5 Hz binaural beats on a 360 Hz carrier: @example aevalsrc="0.1*sin(2*PI*(360-2.5/2)*t) : 0.1*sin(2*PI*(360+2.5/2)*t)" @end example @end itemize @section anullsrc Null audio source, return unprocessed audio frames. It is mainly useful as a template and to be employed in analysis / debugging tools, or as the source for filters which ignore the input data (for example the sox synth filter). It accepts an optional sequence of @var{key}=@var{value} pairs, separated by ":". The description of the accepted options follows. @table @option @item sample_rate, s Specify the sample rate, and defaults to 44100. @item channel_layout, cl Specify the channel layout, and can be either an integer or a string representing a channel layout. The default value of @var{channel_layout} is "stereo". Check the channel_layout_map definition in @file{libavutil/channel_layout.c} for the mapping between strings and channel layout values. @item nb_samples, n Set the number of samples per requested frames. @end table Follow some examples: @example # set the sample rate to 48000 Hz and the channel layout to AV_CH_LAYOUT_MONO. anullsrc=r=48000:cl=4 # same as anullsrc=r=48000:cl=mono @end example @section abuffer Buffer audio frames, and make them available to the filter chain. This source is not intended to be part of user-supplied graph descriptions but for insertion by calling programs through the interface defined in @file{libavfilter/buffersrc.h}. It accepts the following named parameters: @table @option @item time_base Timebase which will be used for timestamps of submitted frames. It must be either a floating-point number or in @var{numerator}/@var{denominator} form. @item sample_rate Audio sample rate. @item sample_fmt Name of the sample format, as returned by @code{av_get_sample_fmt_name()}. @item channel_layout Channel layout of the audio data, in the form that can be accepted by @code{av_get_channel_layout()}. @end table All the parameters need to be explicitly defined. @section flite Synthesize a voice utterance using the libflite library. To enable compilation of this filter you need to configure FFmpeg with @code{--enable-libflite}. Note that the flite library is not thread-safe. The source accepts parameters as a list of @var{key}=@var{value} pairs, separated by ":". The description of the accepted parameters follows. @table @option @item list_voices If set to 1, list the names of the available voices and exit immediately. Default value is 0. @item nb_samples, n Set the maximum number of samples per frame. Default value is 512. @item textfile Set the filename containing the text to speak. @item text Set the text to speak. @item voice, v Set the voice to use for the speech synthesis. Default value is @code{kal}. See also the @var{list_voices} option. @end table @subsection Examples @itemize @item Read from file @file{speech.txt}, and synthetize the text using the standard flite voice: @example flite=textfile=speech.txt @end example @item Read the specified text selecting the @code{slt} voice: @example flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt @end example @item Input text to ffmpeg: @example ffmpeg -f lavfi -i flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt @end example @item Make @file{ffplay} speak the specified text, using @code{flite} and the @code{lavfi} device: @example ffplay -f lavfi flite=text='No more be grieved for which that thou hast done.' @end example @end itemize For more information about libflite, check: @url{http://www.speech.cs.cmu.edu/flite/} @c man end AUDIO SOURCES @chapter Audio Sinks @c man begin AUDIO SINKS Below is a description of the currently available audio sinks. @section abuffersink Buffer audio frames, and make them available to the end of filter chain. This sink is mainly intended for programmatic use, in particular through the interface defined in @file{libavfilter/buffersink.h}. It requires a pointer to an AVABufferSinkContext structure, which defines the incoming buffers' formats, to be passed as the opaque parameter to @code{avfilter_init_filter} for initialization. @section anullsink Null audio sink, do absolutely nothing with the input audio. It is mainly useful as a template and to be employed in analysis / debugging tools. @section abuffersink This sink is intended for programmatic use. Frames that arrive on this sink can be retrieved by the calling program using the interface defined in @file{libavfilter/buffersink.h}. This filter accepts no parameters. @c man end AUDIO SINKS @chapter Video Filters @c man begin VIDEO FILTERS When you configure your FFmpeg build, you can disable any of the existing filters using @code{--disable-filters}. The configure output will show the video filters included in your build. Below is a description of the currently available video filters. @section alphaextract Extract the alpha component from the input as a grayscale video. This is especially useful with the @var{alphamerge} filter. @section alphamerge Add or replace the alpha component of the primary input with the grayscale value of a second input. This is intended for use with @var{alphaextract} to allow the transmission or storage of frame sequences that have alpha in a format that doesn't support an alpha channel. For example, to reconstruct full frames from a normal YUV-encoded video and a separate video created with @var{alphaextract}, you might use: @example movie=in_alpha.mkv [alpha]; [in][alpha] alphamerge [out] @end example Since this filter is designed for reconstruction, it operates on frame sequences without considering timestamps, and terminates when either input reaches end of stream. This will cause problems if your encoding pipeline drops frames. If you're trying to apply an image as an overlay to a video stream, consider the @var{overlay} filter instead. @section ass Same as the @ref{subtitles} filter, except that it doesn't require libavcodec and libavformat to work. On the other hand, it is limited to ASS (Advanced Substation Alpha) subtitles files. @section bbox Compute the bounding box for the non-black pixels in the input frame luminance plane. This filter computes the bounding box containing all the pixels with a luminance value greater than the minimum allowed value. The parameters describing the bounding box are printed on the filter log. @section blackdetect Detect video intervals that are (almost) completely black. Can be useful to detect chapter transitions, commercials, or invalid recordings. Output lines contains the time for the start, end and duration of the detected black interval expressed in seconds. In order to display the output lines, you need to set the loglevel at least to the AV_LOG_INFO value. This filter accepts a list of options in the form of @var{key}=@var{value} pairs separated by ":". A description of the accepted options follows. @table @option @item black_min_duration, d Set the minimum detected black duration expressed in seconds. It must be a non-negative floating point number. Default value is 2.0. @item picture_black_ratio_th, pic_th Set the threshold for considering a picture "black". Express the minimum value for the ratio: @example @var{nb_black_pixels} / @var{nb_pixels} @end example for which a picture is considered black. Default value is 0.98. @item pixel_black_th, pix_th Set the threshold for considering a pixel "black". The threshold expresses the maximum pixel luminance value for which a pixel is considered "black". The provided value is scaled according to the following equation: @example @var{absolute_threshold} = @var{luminance_minimum_value} + @var{pixel_black_th} * @var{luminance_range_size} @end example @var{luminance_range_size} and @var{luminance_minimum_value} depend on the input video format, the range is [0-255] for YUV full-range formats and [16-235] for YUV non full-range formats. Default value is 0.10. @end table The following example sets the maximum pixel threshold to the minimum value, and detects only black intervals of 2 or more seconds: @example blackdetect=d=2:pix_th=0.00 @end example @section blackframe Detect frames that are (almost) completely black. Can be useful to detect chapter transitions or commercials. Output lines consist of the frame number of the detected frame, the percentage of blackness, the position in the file if known or -1 and the timestamp in seconds. In order to display the output lines, you need to set the loglevel at least to the AV_LOG_INFO value. The filter accepts the syntax: @example blackframe[=@var{amount}:[@var{threshold}]] @end example @var{amount} is the percentage of the pixels that have to be below the threshold, and defaults to 98. @var{threshold} is the threshold below which a pixel value is considered black, and defaults to 32. @section boxblur Apply boxblur algorithm to the input video. This filter accepts the parameters: @var{luma_radius}:@var{luma_power}:@var{chroma_radius}:@var{chroma_power}:@var{alpha_radius}:@var{alpha_power} Chroma and alpha parameters are optional, if not specified they default to the corresponding values set for @var{luma_radius} and @var{luma_power}. @var{luma_radius}, @var{chroma_radius}, and @var{alpha_radius} represent the radius in pixels of the box used for blurring the corresponding input plane. They are expressions, and can contain the following constants: @table @option @item w, h the input width and height in pixels @item cw, ch the input chroma image width and height in pixels @item hsub, vsub horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1. @end table The radius must be a non-negative number, and must not be greater than the value of the expression @code{min(w,h)/2} for the luma and alpha planes, and of @code{min(cw,ch)/2} for the chroma planes. @var{luma_power}, @var{chroma_power}, and @var{alpha_power} represent how many times the boxblur filter is applied to the corresponding plane. Some examples follow: @itemize @item Apply a boxblur filter with luma, chroma, and alpha radius set to 2: @example boxblur=2:1 @end example @item Set luma radius to 2, alpha and chroma radius to 0 @example boxblur=2:1:0:0:0:0 @end example @item Set luma and chroma radius to a fraction of the video dimension @example boxblur=min(h\,w)/10:1:min(cw\,ch)/10:1 @end example @end itemize @section colormatrix The colormatrix filter allows conversion between any of the following color space: BT.709 (@var{bt709}), BT.601 (@var{bt601}), SMPTE-240M (@var{smpte240m}) and FCC (@var{fcc}). The syntax of the parameters is @var{source}:@var{destination}: @example colormatrix=bt601:smpte240m @end example @section copy Copy the input source unchanged to the output. Mainly useful for testing purposes. @section crop Crop the input video to @var{out_w}:@var{out_h}:@var{x}:@var{y}:@var{keep_aspect} The @var{keep_aspect} parameter is optional, if specified and set to a non-zero value will force the output display aspect ratio to be the same of the input, by changing the output sample aspect ratio. The @var{out_w}, @var{out_h}, @var{x}, @var{y} parameters are expressions containing the following constants: @table @option @item x, y the computed values for @var{x} and @var{y}. They are evaluated for each new frame. @item in_w, in_h the input width and height @item iw, ih same as @var{in_w} and @var{in_h} @item out_w, out_h the output (cropped) width and height @item ow, oh same as @var{out_w} and @var{out_h} @item a same as @var{iw} / @var{ih} @item sar input sample aspect ratio @item dar input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar} @item hsub, vsub horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1. @item n the number of input frame, starting from 0 @item pos the position in the file of the input frame, NAN if unknown @item t timestamp expressed in seconds, NAN if the input timestamp is unknown @end table The @var{out_w} and @var{out_h} parameters specify the expressions for the width and height of the output (cropped) video. They are evaluated just at the configuration of the filter. The default value of @var{out_w} is "in_w", and the default value of @var{out_h} is "in_h". The expression for @var{out_w} may depend on the value of @var{out_h}, and the expression for @var{out_h} may depend on @var{out_w}, but they cannot depend on @var{x} and @var{y}, as @var{x} and @var{y} are evaluated after @var{out_w} and @var{out_h}. The @var{x} and @var{y} parameters specify the expressions for the position of the top-left corner of the output (non-cropped) area. They are evaluated for each frame. If the evaluated value is not valid, it is approximated to the nearest valid value. The default value of @var{x} is "(in_w-out_w)/2", and the default value for @var{y} is "(in_h-out_h)/2", which set the cropped area at the center of the input image. The expression for @var{x} may depend on @var{y}, and the expression for @var{y} may depend on @var{x}. Follow some examples: @example # crop the central input area with size 100x100 crop=100:100 # crop the central input area with size 2/3 of the input video "crop=2/3*in_w:2/3*in_h" # crop the input video central square crop=in_h # delimit the rectangle with the top-left corner placed at position # 100:100 and the right-bottom corner corresponding to the right-bottom # corner of the input image. crop=in_w-100:in_h-100:100:100 # crop 10 pixels from the left and right borders, and 20 pixels from # the top and bottom borders "crop=in_w-2*10:in_h-2*20" # keep only the bottom right quarter of the input image "crop=in_w/2:in_h/2:in_w/2:in_h/2" # crop height for getting Greek harmony "crop=in_w:1/PHI*in_w" # trembling effect "crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(n/10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(n/7)" # erratic camera effect depending on timestamp "crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(t*13)" # set x depending on the value of y "crop=in_w/2:in_h/2:y:10+10*sin(n/10)" @end example @section cropdetect Auto-detect crop size. Calculate necessary cropping parameters and prints the recommended parameters through the logging system. The detected dimensions correspond to the non-black area of the input video. It accepts the syntax: @example cropdetect[=@var{limit}[:@var{round}[:@var{reset}]]] @end example @table @option @item limit Threshold, which can be optionally specified from nothing (0) to everything (255), defaults to 24. @item round Value which the width/height should be divisible by, defaults to 16. The offset is automatically adjusted to center the video. Use 2 to get only even dimensions (needed for 4:2:2 video). 16 is best when encoding to most video codecs. @item reset Counter that determines after how many frames cropdetect will reset the previously detected largest video area and start over to detect the current optimal crop area. Defaults to 0. This can be useful when channel logos distort the video area. 0 indicates never reset and return the largest area encountered during playback. @end table @section decimate This filter drops frames that do not differ greatly from the previous frame in order to reduce framerate. The main use of this filter is for very-low-bitrate encoding (e.g. streaming over dialup modem), but it could in theory be used for fixing movies that were inverse-telecined incorrectly. It accepts the following parameters: @var{max}:@var{hi}:@var{lo}:@var{frac}. @table @option @item max Set the maximum number of consecutive frames which can be dropped (if positive), or the minimum interval between dropped frames (if negative). If the value is 0, the frame is dropped unregarding the number of previous sequentially dropped frames. Default value is 0. @item hi, lo, frac Set the dropping threshold values. Values for @var{hi} and @var{lo} are for 8x8 pixel blocks and represent actual pixel value differences, so a threshold of 64 corresponds to 1 unit of difference for each pixel, or the same spread out differently over the block. A frame is a candidate for dropping if no 8x8 blocks differ by more than a threshold of @var{hi}, and if no more than @var{frac} blocks (1 meaning the whole image) differ by more than a threshold of @var{lo}. Default value for @var{hi} is 64*12, default value for @var{lo} is 64*5, and default value for @var{frac} is 0.33. @end table @section delogo Suppress a TV station logo by a simple interpolation of the surrounding pixels. Just set a rectangle covering the logo and watch it disappear (and sometimes something even uglier appear - your mileage may vary). The filter accepts parameters as a string of the form "@var{x}:@var{y}:@var{w}:@var{h}:@var{band}", or as a list of @var{key}=@var{value} pairs, separated by ":". The description of the accepted parameters follows. @table @option @item x, y Specify the top left corner coordinates of the logo. They must be specified. @item w, h Specify the width and height of the logo to clear. They must be specified. @item band, t Specify the thickness of the fuzzy edge of the rectangle (added to @var{w} and @var{h}). The default value is 4. @item show When set to 1, a green rectangle is drawn on the screen to simplify finding the right @var{x}, @var{y}, @var{w}, @var{h} parameters, and @var{band} is set to 4. The default value is 0. @end table Some examples follow. @itemize @item Set a rectangle covering the area with top left corner coordinates 0,0 and size 100x77, setting a band of size 10: @example delogo=0:0:100:77:10 @end example @item As the previous example, but use named options: @example delogo=x=0:y=0:w=100:h=77:band=10 @end example @end itemize @section deshake Attempt to fix small changes in horizontal and/or vertical shift. This filter helps remove camera shake from hand-holding a camera, bumping a tripod, moving on a vehicle, etc. The filter accepts parameters as a string of the form "@var{x}:@var{y}:@var{w}:@var{h}:@var{rx}:@var{ry}:@var{edge}:@var{blocksize}:@var{contrast}:@var{search}:@var{filename}" A description of the accepted parameters follows. @table @option @item x, y, w, h Specify a rectangular area where to limit the search for motion vectors. If desired the search for motion vectors can be limited to a rectangular area of the frame defined by its top left corner, width and height. These parameters have the same meaning as the drawbox filter which can be used to visualise the position of the bounding box. This is useful when simultaneous movement of subjects within the frame might be confused for camera motion by the motion vector search. If any or all of @var{x}, @var{y}, @var{w} and @var{h} are set to -1 then the full frame is used. This allows later options to be set without specifying the bounding box for the motion vector search. Default - search the whole frame. @item rx, ry Specify the maximum extent of movement in x and y directions in the range 0-64 pixels. Default 16. @item edge Specify how to generate pixels to fill blanks at the edge of the frame. An integer from 0 to 3 as follows: @table @option @item 0 Fill zeroes at blank locations @item 1 Original image at blank locations @item 2 Extruded edge value at blank locations @item 3 Mirrored edge at blank locations @end table The default setting is mirror edge at blank locations. @item blocksize Specify the blocksize to use for motion search. Range 4-128 pixels, default 8. @item contrast Specify the contrast threshold for blocks. Only blocks with more than the specified contrast (difference between darkest and lightest pixels) will be considered. Range 1-255, default 125. @item search Specify the search strategy 0 = exhaustive search, 1 = less exhaustive search. Default - exhaustive search. @item filename If set then a detailed log of the motion search is written to the specified file. @end table @section drawbox Draw a colored box on the input image. The filter accepts parameters as a list of @var{key}=@var{value} pairs, separated by ":". The description of the accepted parameters follows. @table @option @item x, y Specify the top left corner coordinates of the box. Default to 0. @item width, w @item height, h Specify the width and height of the box, if 0 they are interpreted as the input width and height. Default to 0. @item color, c Specify the color of the box to write, it can be the name of a color (case insensitive match) or a 0xRRGGBB[AA] sequence. If the special value @code{invert} is used, the box edge color is the same as the video with inverted luma. @item thickness, t Set the thickness of the box edge. Default value is @code{4}. @end table If the key of the first options is omitted, the arguments are interpreted according to the following syntax: @example drawbox=@var{x}:@var{y}:@var{width}:@var{height}:@var{color}:@var{thickness} @end example Some examples follow: @itemize @item Draw a black box around the edge of the input image: @example drawbox @end example @item Draw a box with color red and an opacity of 50%: @example drawbox=10:20:200:60:red@@0.5 @end example The previous example can be specified as: @example drawbox=x=10:y=20:w=200:h=60:color=red@@0.5 @end example @item Fill the box with pink color: @example drawbox=x=10:y=10:w=100:h=100:color=pink@@0.5:t=max @end example @end itemize @anchor{drawtext} @section drawtext Draw text string or text from specified file on top of video using the libfreetype library. To enable compilation of this filter you need to configure FFmpeg with @code{--enable-libfreetype}. @subsection Syntax The filter accepts parameters as a list of @var{key}=@var{value} pairs, separated by ":". The description of the accepted parameters follows. @table @option @item box Used to draw a box around text using background color. Value should be either 1 (enable) or 0 (disable). The default value of @var{box} is 0. @item boxcolor The color to be used for drawing box around text. Either a string (e.g. "yellow") or in 0xRRGGBB[AA] format (e.g. "0xff00ff"), possibly followed by an alpha specifier. The default value of @var{boxcolor} is "white". @item draw Set an expression which specifies if the text should be drawn. If the expression evaluates to 0, the text is not drawn. This is useful for specifying that the text should be drawn only when specific conditions are met. Default value is "1". See below for the list of accepted constants and functions. @item expansion Select how the @var{text} is expanded. Can be either @code{none}, @code{strftime} (default for compatibity reasons but deprecated) or @code{normal}. See the @ref{drawtext_expansion, Text expansion} section below for details. @item fix_bounds If true, check and fix text coords to avoid clipping. @item fontcolor The color to be used for drawing fonts. Either a string (e.g. "red") or in 0xRRGGBB[AA] format (e.g. "0xff000033"), possibly followed by an alpha specifier. The default value of @var{fontcolor} is "black". @item fontfile The font file to be used for drawing text. Path must be included. This parameter is mandatory. @item fontsize The font size to be used for drawing text. The default value of @var{fontsize} is 16. @item ft_load_flags Flags to be used for loading the fonts. The flags map the corresponding flags supported by libfreetype, and are a combination of the following values: @table @var @item default @item no_scale @item no_hinting @item render @item no_bitmap @item vertical_layout @item force_autohint @item crop_bitmap @item pedantic @item ignore_global_advance_width @item no_recurse @item ignore_transform @item monochrome @item linear_design @item no_autohint @item end table @end table Default value is "render". For more information consult the documentation for the FT_LOAD_* libfreetype flags. @item shadowcolor The color to be used for drawing a shadow behind the drawn text. It can be a color name (e.g. "yellow") or a string in the 0xRRGGBB[AA] form (e.g. "0xff00ff"), possibly followed by an alpha specifier. The default value of @var{shadowcolor} is "black". @item shadowx, shadowy The x and y offsets for the text shadow position with respect to the position of the text. They can be either positive or negative values. Default value for both is "0". @item tabsize The size in number of spaces to use for rendering the tab. Default value is 4. @item timecode Set the initial timecode representation in "hh:mm:ss[:;.]ff" format. It can be used with or without text parameter. @var{timecode_rate} option must be specified. @item timecode_rate, rate, r Set the timecode frame rate (timecode only). @item text The text string to be drawn. The text must be a sequence of UTF-8 encoded characters. This parameter is mandatory if no file is specified with the parameter @var{textfile}. @item textfile A text file containing text to be drawn. The text must be a sequence of UTF-8 encoded characters. This parameter is mandatory if no text string is specified with the parameter @var{text}. If both @var{text} and @var{textfile} are specified, an error is thrown. @item reload If set to 1, the @var{textfile} will be reloaded before each frame. Be sure to update it atomically, or it may be read partially, or even fail. @item x, y The expressions which specify the offsets where text will be drawn within the video frame. They are relative to the top/left border of the output image. The default value of @var{x} and @var{y} is "0". See below for the list of accepted constants and functions. @end table The parameters for @var{x} and @var{y} are expressions containing the following constants and functions: @table @option @item dar input display aspect ratio, it is the same as (@var{w} / @var{h}) * @var{sar} @item hsub, vsub horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1. @item line_h, lh the height of each text line @item main_h, h, H the input height @item main_w, w, W the input width @item max_glyph_a, ascent the maximum distance from the baseline to the highest/upper grid coordinate used to place a glyph outline point, for all the rendered glyphs. It is a positive value, due to the grid's orientation with the Y axis upwards. @item max_glyph_d, descent the maximum distance from the baseline to the lowest grid coordinate used to place a glyph outline point, for all the rendered glyphs. This is a negative value, due to the grid's orientation, with the Y axis upwards. @item max_glyph_h maximum glyph height, that is the maximum height for all the glyphs contained in the rendered text, it is equivalent to @var{ascent} - @var{descent}. @item max_glyph_w maximum glyph width, that is the maximum width for all the glyphs contained in the rendered text @item n the number of input frame, starting from 0 @item rand(min, max) return a random number included between @var{min} and @var{max} @item sar input sample aspect ratio @item t timestamp expressed in seconds, NAN if the input timestamp is unknown @item text_h, th the height of the rendered text @item text_w, tw the width of the rendered text @item x, y the x and y offset coordinates where the text is drawn. These parameters allow the @var{x} and @var{y} expressions to refer each other, so you can for example specify @code{y=x/dar}. @end table If libavfilter was built with @code{--enable-fontconfig}, then @option{fontfile} can be a fontconfig pattern or omitted. @anchor{drawtext_expansion} @subsection Text expansion If @option{expansion} is set to @code{strftime} (which is the default for now), the filter recognizes strftime() sequences in the provided text and expands them accordingly. Check the documentation of strftime(). This feature is deprecated. If @option{expansion} is set to @code{none}, the text is printed verbatim. If @option{expansion} is set to @code{normal} (which will be the default), the following expansion mechanism is used. The backslash character '\', followed by any character, always expands to the second character. Sequence of the form @code{%@{...@}} are expanded. The text between the braces is a function name, possibly followed by arguments separated by ':'. If the arguments contain special characters or delimiters (':' or '@}'), they should be escaped. Note that they probably must also be escaped as the value for the @option{text} option in the filter argument string and as the filter argument in the filter graph description, and possibly also for the shell, that makes up to four levels of escaping; using a text file avoids these problems. The following functions are available: @table @command @item expr, e The expression evaluation result. It must take one argument specifying the expression to be evaluated, which accepts the same constants and functions as the @var{x} and @var{y} values. Note that not all constants should be used, for example the text size is not known when evaluating the expression, so the constants @var{text_w} and @var{text_h} will have an undefined value. @item gmtime The time at which the filter is running, expressed in UTC. It can accept an argument: a strftime() format string. @item localtime The time at which the filter is running, expressed in the local time zone. It can accept an argument: a strftime() format string. @item n, frame_num The frame number, starting from 0. @item pts The timestamp of the current frame, in seconds, with microsecond accuracy. @end table @subsection Examples Some examples follow. @itemize @item Draw "Test Text" with font FreeSerif, using the default values for the optional parameters. @example drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'" @end example @item Draw 'Test Text' with font FreeSerif of size 24 at position x=100 and y=50 (counting from the top-left corner of the screen), text is yellow with a red box around it. Both the text and the box have an opacity of 20%. @example drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\ x=100: y=50: fontsize=24: fontcolor=yellow@@0.2: box=1: boxcolor=red@@0.2" @end example Note that the double quotes are not necessary if spaces are not used within the parameter list. @item Show the text at the center of the video frame: @example drawtext="fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=(w-text_w)/2:y=(h-text_h-line_h)/2" @end example @item Show a text line sliding from right to left in the last row of the video frame. The file @file{LONG_LINE} is assumed to contain a single line with no newlines. @example drawtext="fontsize=15:fontfile=FreeSerif.ttf:text=LONG_LINE:y=h-line_h:x=-50*t" @end example @item Show the content of file @file{CREDITS} off the bottom of the frame and scroll up. @example drawtext="fontsize=20:fontfile=FreeSerif.ttf:textfile=CREDITS:y=h-20*t" @end example @item Draw a single green letter "g", at the center of the input video. The glyph baseline is placed at half screen height. @example drawtext="fontsize=60:fontfile=FreeSerif.ttf:fontcolor=green:text=g:x=(w-max_glyph_w)/2:y=h/2-ascent" @end example @item Show text for 1 second every 3 seconds: @example drawtext="fontfile=FreeSerif.ttf:fontcolor=white:x=100:y=x/dar:draw=lt(mod(t\,3)\,1):text='blink'" @end example @item Use fontconfig to set the font. Note that the colons need to be escaped. @example drawtext='fontfile=Linux Libertine O-40\:style=Semibold:text=FFmpeg' @end example @item Print the date of a real-time encoding (see strftime(3)): @example drawtext='fontfile=FreeSans.ttf:expansion=normal:text=%@{localtime:%a %b %d %Y@}' @end example @end itemize For more information about libfreetype, check: @url{http://www.freetype.org/}. For more information about fontconfig, check: @url{http://freedesktop.org/software/fontconfig/fontconfig-user.html}. @section edgedetect Detect and draw edges. The filter uses the Canny Edge Detection algorithm. This filter accepts the following optional named parameters: @table @option @item low, high Set low and high threshold values used by the Canny thresholding algorithm. The high threshold selects the "strong" edge pixels, which are then connected through 8-connectivity with the "weak" edge pixels selected by the low threshold. @var{low} and @var{high} threshold values must be choosen in the range [0,1], and @var{low} should be lesser or equal to @var{high}. Default value for @var{low} is @code{20/255}, and default value for @var{high} is @code{50/255}. @end table Example: @example edgedetect=low=0.1:high=0.4 @end example @section fade Apply fade-in/out effect to input video. It accepts the parameters: @var{type}:@var{start_frame}:@var{nb_frames}[:@var{options}] @var{type} specifies if the effect type, can be either "in" for fade-in, or "out" for a fade-out effect. @var{start_frame} specifies the number of the start frame for starting to apply the fade effect. @var{nb_frames} specifies the number of frames for which the fade effect has to last. At the end of the fade-in effect the output video will have the same intensity as the input video, at the end of the fade-out transition the output video will be completely black. @var{options} is an optional sequence of @var{key}=@var{value} pairs, separated by ":". The description of the accepted options follows. @table @option @item type, t See @var{type}. @item start_frame, s See @var{start_frame}. @item nb_frames, n See @var{nb_frames}. @item alpha If set to 1, fade only alpha channel, if one exists on the input. Default value is 0. @end table A few usage examples follow, usable too as test scenarios. @example # fade in first 30 frames of video fade=in:0:30 # fade out last 45 frames of a 200-frame video fade=out:155:45 # fade in first 25 frames and fade out last 25 frames of a 1000-frame video fade=in:0:25, fade=out:975:25 # make first 5 frames black, then fade in from frame 5-24 fade=in:5:20 # fade in alpha over first 25 frames of video fade=in:0:25:alpha=1 @end example @section field Extract a single field from an interlaced image using stride arithmetic to avoid wasting CPU time. The output frames are marked as non-interlaced. This filter accepts the following named options: @table @option @item type Specify whether to extract the top (if the value is @code{0} or @code{top}) or the bottom field (if the value is @code{1} or @code{bottom}). @end table If the option key is not specified, the first value sets the @var{type} option. For example: @example field=bottom @end example is equivalent to: @example field=type=bottom @end example @section fieldorder Transform the field order of the input video. It accepts one parameter which specifies the required field order that the input interlaced video will be transformed to. The parameter can assume one of the following values: @table @option @item 0 or bff output bottom field first @item 1 or tff output top field first @end table Default value is "tff". Transformation is achieved by shifting the picture content up or down by one line, and filling the remaining line with appropriate picture content. This method is consistent with most broadcast field order converters. If the input video is not flagged as being interlaced, or it is already flagged as being of the required output field order then this filter does not alter the incoming video. This filter is very useful when converting to or from PAL DV material, which is bottom field first. For example: @example ffmpeg -i in.vob -vf "fieldorder=bff" out.dv @end example @section fifo Buffer input images and send them when they are requested. This filter is mainly useful when auto-inserted by the libavfilter framework. The filter does not take parameters. @section format Convert the input video to one of the specified pixel formats. Libavfilter will try to pick one that is supported for the input to the next filter. The filter accepts a list of pixel format names, separated by ":", for example "yuv420p:monow:rgb24". Some examples follow: @example # convert the input video to the format "yuv420p" format=yuv420p # convert the input video to any of the formats in the list format=yuv420p:yuv444p:yuv410p @end example @section fps Convert the video to specified constant framerate by duplicating or dropping frames as necessary. This filter accepts the following named parameters: @table @option @item fps Desired output framerate. The default is @code{25}. @item round Rounding method. Possible values are: @table @option @item zero zero round towards 0 @item inf round away from 0 @item down round towards -infinity @item up round towards +infinity @item near round to nearest @end table The default is @code{near}. @end table Alternatively, the options can be specified as a flat string: @var{fps}[:@var{round}]. See also the @ref{setpts} filter. @section framestep Select one frame every N. This filter accepts in input a string representing a positive integer. Default argument is @code{1}. @anchor{frei0r} @section frei0r Apply a frei0r effect to the input video. To enable compilation of this filter you need to install the frei0r header and configure FFmpeg with @code{--enable-frei0r}. The filter supports the syntax: @example @var{filter_name}[@{:|=@}@var{param1}:@var{param2}:...:@var{paramN}] @end example @var{filter_name} is the name of the frei0r effect to load. If the environment variable @env{FREI0R_PATH} is defined, the frei0r effect is searched in each one of the directories specified by the colon (or semicolon on Windows platforms) separated list in @env{FREIOR_PATH}, otherwise in the standard frei0r paths, which are in this order: @file{HOME/.frei0r-1/lib/}, @file{/usr/local/lib/frei0r-1/}, @file{/usr/lib/frei0r-1/}. @var{param1}, @var{param2}, ... , @var{paramN} specify the parameters for the frei0r effect. A frei0r effect parameter can be a boolean (whose values are specified with "y" and "n"), a double, a color (specified by the syntax @var{R}/@var{G}/@var{B}, @var{R}, @var{G}, and @var{B} being float numbers from 0.0 to 1.0) or by an @code{av_parse_color()} color description), a position (specified by the syntax @var{X}/@var{Y}, @var{X} and @var{Y} being float numbers) and a string. The number and kind of parameters depend on the loaded effect. If an effect parameter is not specified the default value is set. Some examples follow: @itemize @item Apply the distort0r effect, set the first two double parameters: @example frei0r=distort0r:0.5:0.01 @end example @item Apply the colordistance effect, take a color as first parameter: @example frei0r=colordistance:0.2/0.3/0.4 frei0r=colordistance:violet frei0r=colordistance:0x112233 @end example @item Apply the perspective effect, specify the top left and top right image positions: @example frei0r=perspective:0.2/0.2:0.8/0.2 @end example @end itemize For more information see: @url{http://frei0r.dyne.org} @section geq The filter takes one, two or three equations as parameter, separated by ':'. The first equation is mandatory and applies to the luma plane. The two following are respectively for chroma blue and chroma red planes. The filter syntax allows named parameters: @table @option @item lum_expr the luminance expression @item cb_expr the chrominance blue expression @item cr_expr the chrominance red expression @end table If one of the chrominance expression is not defined, it falls back on the other one. If none of them are specified, they will evaluate the luminance expression. The expressions can use the following variables and functions: @table @option @item N The sequential number of the filtered frame, starting from @code{0}. @item X, Y The coordinates of the current sample. @item W, H The width and height of the image. @item SW, SH Width and height scale depending on the currently filtered plane. It is the ratio between the corresponding luma plane number of pixels and the current plane ones. E.g. for YUV4:2:0 the values are @code{1,1} for the luma plane, and @code{0.5,0.5} for chroma planes. @item T Time of the current frame, expressed in seconds. @item p(x, y) Return the value of the pixel at location (@var{x},@var{y}) of the current plane. @item lum(x, y) Return the value of the pixel at location (@var{x},@var{y}) of the luminance plane. @item cb(x, y) Return the value of the pixel at location (@var{x},@var{y}) of the blue-difference chroma plane. @item cr(x, y) Return the value of the pixel at location (@var{x},@var{y}) of the red-difference chroma plane. @end table For functions, if @var{x} and @var{y} are outside the area, the value will be automatically clipped to the closer edge. Some examples follow: @itemize @item Flip the image horizontally: @example geq=p(W-X\,Y) @end example @item Generate a bidimensional sine wave, with angle @code{PI/3} and a wavelength of 100 pixels: @example geq=128 + 100*sin(2*(PI/100)*(cos(PI/3)*(X-50*T) + sin(PI/3)*Y)):128:128 @end example @item Generate a fancy enigmatic moving light: @example nullsrc=s=256x256,geq=random(1)/hypot(X-cos(N*0.07)*W/2-W/2\,Y-sin(N*0.09)*H/2-H/2)^2*1000000*sin(N*0.02):128:128 @end example @end itemize @section gradfun Fix the banding artifacts that are sometimes introduced into nearly flat regions by truncation to 8bit color depth. Interpolate the gradients that should go where the bands are, and dither them. This filter is designed for playback only. Do not use it prior to lossy compression, because compression tends to lose the dither and bring back the bands. The filter takes two optional parameters, separated by ':': @var{strength}:@var{radius} @var{strength} is the maximum amount by which the filter will change any one pixel. Also the threshold for detecting nearly flat regions. Acceptable values range from .51 to 255, default value is 1.2, out-of-range values will be clipped to the valid range. @var{radius} is the neighborhood to fit the gradient to. A larger radius makes for smoother gradients, but also prevents the filter from modifying the pixels near detailed regions. Acceptable values are 8-32, default value is 16, out-of-range values will be clipped to the valid range. @example # default parameters gradfun=1.2:16 # omitting radius gradfun=1.2 @end example @section hflip Flip the input video horizontally. For example to horizontally flip the input video with @command{ffmpeg}: @example ffmpeg -i in.avi -vf "hflip" out.avi @end example @section hqdn3d High precision/quality 3d denoise filter. This filter aims to reduce image noise producing smooth images and making still images really still. It should enhance compressibility. It accepts the following optional parameters: @var{luma_spatial}:@var{chroma_spatial}:@var{luma_tmp}:@var{chroma_tmp} @table @option @item luma_spatial a non-negative float number which specifies spatial luma strength, defaults to 4.0 @item chroma_spatial a non-negative float number which specifies spatial chroma strength, defaults to 3.0*@var{luma_spatial}/4.0 @item luma_tmp a float number which specifies luma temporal strength, defaults to 6.0*@var{luma_spatial}/4.0 @item chroma_tmp a float number which specifies chroma temporal strength, defaults to @var{luma_tmp}*@var{chroma_spatial}/@var{luma_spatial} @end table @section hue Modify the hue and/or the saturation of the input. This filter accepts the following optional named options: @table @option @item h Specify the hue angle as a number of degrees. It accepts a float number or an expression, and defaults to 0.0. @item H Specify the hue angle as a number of degrees. It accepts a float number or an expression, and defaults to 0.0. @item s Specify the saturation in the [-10,10] range. It accepts a float number and defaults to 1.0. @end table The @var{h}, @var{H} and @var{s} parameters are expressions containing the following constants: @table @option @item n frame count of the input frame starting from 0 @item pts presentation timestamp of the input frame expressed in time base units @item r frame rate of the input video, NAN if the input frame rate is unknown @item t timestamp expressed in seconds, NAN if the input timestamp is unknown @item tb time base of the input video @end table The options can also be set using the syntax: @var{hue}:@var{saturation} In this case @var{hue} is expressed in degrees. Some examples follow: @itemize @item Set the hue to 90 degrees and the saturation to 1.0: @example hue=h=90:s=1 @end example @item Same command but expressing the hue in radians: @example hue=H=PI/2:s=1 @end example @item Same command without named options, hue must be expressed in degrees: @example hue=90:1 @end example @item Note that "h:s" syntax does not support expressions for the values of h and s, so the following example will issue an error: @example hue=PI/2:1 @end example @item Rotate hue and make the saturation swing between 0 and 2 over a period of 1 second: @example hue="H=2*PI*t: s=sin(2*PI*t)+1" @end example @item Apply a 3 seconds saturation fade-in effect starting at 0: @example hue="s=min(t/3\,1)" @end example The general fade-in expression can be written as: @example hue="s=min(0\, max((t-START)/DURATION\, 1))" @end example @item Apply a 3 seconds saturation fade-out effect starting at 5 seconds: @example hue="s=max(0\, min(1\, (8-t)/3))" @end example The general fade-out expression can be written as: @example hue="s=max(0\, min(1\, (START+DURATION-t)/DURATION))" @end example @end itemize @subsection Commands This filter supports the following command: @table @option @item reinit Modify the hue and/or the saturation of the input video. The command accepts the same named options and syntax than when calling the filter from the command-line. If a parameter is omitted, it is kept at its current value. @end table @section idet Interlaceing detect filter. This filter tries to detect if the input is interlaced or progressive. Top or bottom field first. @section lut, lutrgb, lutyuv Compute a look-up table for binding each pixel component input value to an output value, and apply it to input video. @var{lutyuv} applies a lookup table to a YUV input video, @var{lutrgb} to an RGB input video. These filters accept in input a ":"-separated list of options, which specify the expressions used for computing the lookup table for the corresponding pixel component values. The @var{lut} filter requires either YUV or RGB pixel formats in input, and accepts the options: @table @option @item @var{c0} (first pixel component) @item @var{c1} (second pixel component) @item @var{c2} (third pixel component) @item @var{c3} (fourth pixel component, corresponds to the alpha component) @end table The exact component associated to each option depends on the format in input. The @var{lutrgb} filter requires RGB pixel formats in input, and accepts the options: @table @option @item @var{r} (red component) @item @var{g} (green component) @item @var{b} (blue component) @item @var{a} (alpha component) @end table The @var{lutyuv} filter requires YUV pixel formats in input, and accepts the options: @table @option @item @var{y} (Y/luminance component) @item @var{u} (U/Cb component) @item @var{v} (V/Cr component) @item @var{a} (alpha component) @end table The expressions can contain the following constants and functions: @table @option @item w, h the input width and height @item val input value for the pixel component @item clipval the input value clipped in the @var{minval}-@var{maxval} range @item maxval maximum value for the pixel component @item minval minimum value for the pixel component @item negval the negated value for the pixel component value clipped in the @var{minval}-@var{maxval} range , it corresponds to the expression "maxval-clipval+minval" @item clip(val) the computed value in @var{val} clipped in the @var{minval}-@var{maxval} range @item gammaval(gamma) the computed gamma correction value of the pixel component value clipped in the @var{minval}-@var{maxval} range, corresponds to the expression "pow((clipval-minval)/(maxval-minval)\,@var{gamma})*(maxval-minval)+minval" @end table All expressions default to "val". Some examples follow: @example # negate input video lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val" lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val" # the above is the same as lutrgb="r=negval:g=negval:b=negval" lutyuv="y=negval:u=negval:v=negval" # negate luminance lutyuv=y=negval # remove chroma components, turns the video into a graytone image lutyuv="u=128:v=128" # apply a luma burning effect lutyuv="y=2*val" # remove green and blue components lutrgb="g=0:b=0" # set a constant alpha channel value on input format=rgba,lutrgb=a="maxval-minval/2" # correct luminance gamma by a 0.5 factor lutyuv=y=gammaval(0.5) @end example @section mp Apply an MPlayer filter to the input video. This filter provides a wrapper around most of the filters of MPlayer/MEncoder. This wrapper is considered experimental. Some of the wrapped filters may not work properly and we may drop support for them, as they will be implemented natively into FFmpeg. Thus you should avoid depending on them when writing portable scripts. The filters accepts the parameters: @var{filter_name}[:=]@var{filter_params} @var{filter_name} is the name of a supported MPlayer filter, @var{filter_params} is a string containing the parameters accepted by the named filter. The list of the currently supported filters follows: @table @var @item detc @item dint @item divtc @item down3dright @item dsize @item eq2 @item eq @item fil @item fspp @item harddup @item il @item ilpack @item ivtc @item kerndeint @item mcdeint @item noise @item ow @item perspective @item phase @item pp7 @item pullup @item qp @item sab @item softpulldown @item softskip @item spp @item telecine @item tinterlace @item unsharp @item uspp @end table The parameter syntax and behavior for the listed filters are the same of the corresponding MPlayer filters. For detailed instructions check the "VIDEO FILTERS" section in the MPlayer manual. Some examples follow: @itemize @item Adjust gamma, brightness, contrast: @example mp=eq2=1.0:2:0.5 @end example @item Add temporal noise to input video: @example mp=noise=20t @end example @end itemize See also mplayer(1), @url{http://www.mplayerhq.hu/}. @section negate Negate input video. This filter accepts an integer in input, if non-zero it negates the alpha component (if available). The default value in input is 0. @section noformat Force libavfilter not to use any of the specified pixel formats for the input to the next filter. The filter accepts a list of pixel format names, separated by ":", for example "yuv420p:monow:rgb24". Some examples follow: @example # force libavfilter to use a format different from "yuv420p" for the # input to the vflip filter noformat=yuv420p,vflip # convert the input video to any of the formats not contained in the list noformat=yuv420p:yuv444p:yuv410p @end example @section null Pass the video source unchanged to the output. @section ocv Apply video transform using libopencv. To enable this filter install libopencv library and headers and configure FFmpeg with @code{--enable-libopencv}. The filter takes the parameters: @var{filter_name}@{:=@}@var{filter_params}. @var{filter_name} is the name of the libopencv filter to apply. @var{filter_params} specifies the parameters to pass to the libopencv filter. If not specified the default values are assumed. Refer to the official libopencv documentation for more precise information: @url{http://opencv.willowgarage.com/documentation/c/image_filtering.html} Follows the list of supported libopencv filters. @anchor{dilate} @subsection dilate Dilate an image by using a specific structuring element. This filter corresponds to the libopencv function @code{cvDilate}. It accepts the parameters: @var{struct_el}:@var{nb_iterations}. @var{struct_el} represents a structuring element, and has the syntax: @var{cols}x@var{rows}+@var{anchor_x}x@var{anchor_y}/@var{shape} @var{cols} and @var{rows} represent the number of columns and rows of the structuring element, @var{anchor_x} and @var{anchor_y} the anchor point, and @var{shape} the shape for the structuring element, and can be one of the values "rect", "cross", "ellipse", "custom". If the value for @var{shape} is "custom", it must be followed by a string of the form "=@var{filename}". The file with name @var{filename} is assumed to represent a binary image, with each printable character corresponding to a bright pixel. When a custom @var{shape} is used, @var{cols} and @var{rows} are ignored, the number or columns and rows of the read file are assumed instead. The default value for @var{struct_el} is "3x3+0x0/rect". @var{nb_iterations} specifies the number of times the transform is applied to the image, and defaults to 1. Follow some example: @example # use the default values ocv=dilate # dilate using a structuring element with a 5x5 cross, iterate two times ocv=dilate=5x5+2x2/cross:2 # read the shape from the file diamond.shape, iterate two times # the file diamond.shape may contain a pattern of characters like this: # * # *** # ***** # *** # * # the specified cols and rows are ignored (but not the anchor point coordinates) ocv=0x0+2x2/custom=diamond.shape:2 @end example @subsection erode Erode an image by using a specific structuring element. This filter corresponds to the libopencv function @code{cvErode}. The filter accepts the parameters: @var{struct_el}:@var{nb_iterations}, with the same syntax and semantics as the @ref{dilate} filter. @subsection smooth Smooth the input video. The filter takes the following parameters: @var{type}:@var{param1}:@var{param2}:@var{param3}:@var{param4}. @var{type} is the type of smooth filter to apply, and can be one of the following values: "blur", "blur_no_scale", "median", "gaussian", "bilateral". The default value is "gaussian". @var{param1}, @var{param2}, @var{param3}, and @var{param4} are parameters whose meanings depend on smooth type. @var{param1} and @var{param2} accept integer positive values or 0, @var{param3} and @var{param4} accept float values. The default value for @var{param1} is 3, the default value for the other parameters is 0. These parameters correspond to the parameters assigned to the libopencv function @code{cvSmooth}. @anchor{overlay} @section overlay Overlay one video on top of another. It takes two inputs and one output, the first input is the "main" video on which the second input is overlayed. It accepts the parameters: @var{x}:@var{y}[:@var{options}]. @var{x} is the x coordinate of the overlayed video on the main video, @var{y} is the y coordinate. @var{x} and @var{y} are expressions containing the following parameters: @table @option @item main_w, main_h main input width and height @item W, H same as @var{main_w} and @var{main_h} @item overlay_w, overlay_h overlay input width and height @item w, h same as @var{overlay_w} and @var{overlay_h} @end table @var{options} is an optional list of @var{key}=@var{value} pairs, separated by ":". The description of the accepted options follows. @table @option @item rgb If set to 1, force the filter to accept inputs in the RGB color space. Default value is 0. @end table Be aware that frames are taken from each input video in timestamp order, hence, if their initial timestamps differ, it is a a good idea to pass the two inputs through a @var{setpts=PTS-STARTPTS} filter to have them begin in the same zero timestamp, as it does the example for the @var{movie} filter. Follow some examples: @example # draw the overlay at 10 pixels from the bottom right # corner of the main video. overlay=main_w-overlay_w-10:main_h-overlay_h-10 # insert a transparent PNG logo in the bottom left corner of the input ffmpeg -i input -i logo -filter_complex 'overlay=10:main_h-overlay_h-10' output # insert 2 different transparent PNG logos (second logo on bottom # right corner): ffmpeg -i input -i logo1 -i logo2 -filter_complex 'overlay=10:H-h-10,overlay=W-w-10:H-h-10' output # add a transparent color layer on top of the main video, # WxH specifies the size of the main input to the overlay filter color=red@@.3:WxH [over]; [in][over] overlay [out] # play an original video and a filtered version (here with the deshake filter) # side by side ffplay input.avi -vf 'split[a][b]; [a]pad=iw*2:ih[src]; [b]deshake[filt]; [src][filt]overlay=w' # the previous example is the same as: ffplay input.avi -vf 'split[b], pad=iw*2[src], [b]deshake, [src]overlay=w' @end example You can chain together more overlays but the efficiency of such approach is yet to be tested. @section pad Add paddings to the input image, and places the original input at the given coordinates @var{x}, @var{y}. It accepts the following parameters: @var{width}:@var{height}:@var{x}:@var{y}:@var{color}. The parameters @var{width}, @var{height}, @var{x}, and @var{y} are expressions containing the following constants: @table @option @item in_w, in_h the input video width and height @item iw, ih same as @var{in_w} and @var{in_h} @item out_w, out_h the output width and height, that is the size of the padded area as specified by the @var{width} and @var{height} expressions @item ow, oh same as @var{out_w} and @var{out_h} @item x, y x and y offsets as specified by the @var{x} and @var{y} expressions, or NAN if not yet specified @item a same as @var{iw} / @var{ih} @item sar input sample aspect ratio @item dar input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar} @item hsub, vsub horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1. @end table Follows the description of the accepted parameters. @table @option @item width, height Specify the size of the output image with the paddings added. If the value for @var{width} or @var{height} is 0, the corresponding input size is used for the output. The @var{width} expression can reference the value set by the @var{height} expression, and vice versa. The default value of @var{width} and @var{height} is 0. @item x, y Specify the offsets where to place the input image in the padded area with respect to the top/left border of the output image. The @var{x} expression can reference the value set by the @var{y} expression, and vice versa. The default value of @var{x} and @var{y} is 0. @item color Specify the color of the padded area, it can be the name of a color (case insensitive match) or a 0xRRGGBB[AA] sequence. The default value of @var{color} is "black". @end table @subsection Examples @itemize @item Add paddings with color "violet" to the input video. Output video size is 640x480, the top-left corner of the input video is placed at column 0, row 40: @example pad=640:480:0:40:violet @end example @item Pad the input to get an output with dimensions increased by 3/2, and put the input video at the center of the padded area: @example pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2" @end example @item Pad the input to get a squared output with size equal to the maximum value between the input width and height, and put the input video at the center of the padded area: @example pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2" @end example @item Pad the input to get a final w/h ratio of 16:9: @example pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2" @end example @item In case of anamorphic video, in order to set the output display aspect correctly, it is necessary to use @var{sar} in the expression, according to the relation: @example (ih * X / ih) * sar = output_dar X = output_dar / sar @end example Thus the previous example needs to be modified to: @example pad="ih*16/9/sar:ih:(ow-iw)/2:(oh-ih)/2" @end example @item Double output size and put the input video in the bottom-right corner of the output padded area: @example pad="2*iw:2*ih:ow-iw:oh-ih" @end example @end itemize @section pixdesctest Pixel format descriptor test filter, mainly useful for internal testing. The output video should be equal to the input video. For example: @example format=monow, pixdesctest @end example can be used to test the monowhite pixel format descriptor definition. @section removelogo Suppress a TV station logo, using an image file to determine which pixels comprise the logo. It works by filling in the pixels that comprise the logo with neighboring pixels. This filter requires one argument which specifies the filter bitmap file, which can be any image format supported by libavformat. The width and height of the image file must match those of the video stream being processed. Pixels in the provided bitmap image with a value of zero are not considered part of the logo, non-zero pixels are considered part of the logo. If you use white (255) for the logo and black (0) for the rest, you will be safe. For making the filter bitmap, it is recommended to take a screen capture of a black frame with the logo visible, and then using a threshold filter followed by the erode filter once or twice. If needed, little splotches can be fixed manually. Remember that if logo pixels are not covered, the filter quality will be much reduced. Marking too many pixels as part of the logo does not hurt as much, but it will increase the amount of blurring needed to cover over the image and will destroy more information than necessary, and extra pixels will slow things down on a large logo. @section scale Scale (resize) the input video, using the libswscale library. The scale filter forces the output display aspect ratio to be the same of the input, by changing the output sample aspect ratio. This filter accepts a list of named options in the form of @var{key}=@var{value} pairs separated by ":". If the key for the first two options is not specified, the assumed keys for the first two values are @code{w} and @code{h}. If the first option has no key and can be interpreted like a video size specification, it will be used to set the video size. A description of the accepted options follows. @table @option @item width, w Set the video width expression, default value is @code{iw}. See below for the list of accepted constants. @item height, h Set the video heiht expression, default value is @code{ih}. See below for the list of accepted constants. @item interl Set the interlacing. It accepts the following values: @table @option @item 1 force interlaced aware scaling @item 0 do not apply interlaced scaling @item -1 select interlaced aware scaling depending on whether the source frames are flagged as interlaced or not @end table Default value is @code{0}. @item flags Set libswscale scaling flags. If not explictly specified the filter applies a bilinear scaling algorithm. @item size, s Set the video size, the value must be a valid abbreviation or in the form @var{width}x@var{height}. @end table The values of the @var{w} and @var{h} options are expressions containing the following constants: @table @option @item in_w, in_h the input width and height @item iw, ih same as @var{in_w} and @var{in_h} @item out_w, out_h the output (cropped) width and height @item ow, oh same as @var{out_w} and @var{out_h} @item a same as @var{iw} / @var{ih} @item sar input sample aspect ratio @item dar input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar} @item hsub, vsub horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1. @end table If the input image format is different from the format requested by the next filter, the scale filter will convert the input to the requested format. If the value for @var{width} or @var{height} is 0, the respective input size is used for the output. If the value for @var{width} or @var{height} is -1, the scale filter will use, for the respective output size, a value that maintains the aspect ratio of the input image. @subsection Examples @itemize @item Scale the input video to a size of 200x100: @example scale=200:100 @end example This is equivalent to: @example scale=w=200:h=100 @end example or: @example scale=200x100 @end example @item Specify a size abbreviation for the output size: @example scale=qcif @end example which can also be written as: @example scale=size=qcif @end example @item Scale the input to 2x: @example scale=2*iw:2*ih @end example @item The above is the same as: @example scale=2*in_w:2*in_h @end example @item Scale the input to 2x with forced interlaced scaling: @example scale=2*iw:2*ih:interl=1 @end example @item Scale the input to half size: @example scale=iw/2:ih/2 @end example @item Increase the width, and set the height to the same size: @example scale=3/2*iw:ow @end example @item Seek for Greek harmony: @example scale=iw:1/PHI*iw scale=ih*PHI:ih @end example @item Increase the height, and set the width to 3/2 of the height: @example scale=3/2*oh:3/5*ih @end example @item Increase the size, but make the size a multiple of the chroma: @example scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub" @end example @item Increase the width to a maximum of 500 pixels, keep the same input aspect ratio: @example scale='min(500\, iw*3/2):-1' @end example @end itemize @section setdar, setsar The @code{setdar} filter sets the Display Aspect Ratio for the filter output video. This is done by changing the specified Sample (aka Pixel) Aspect Ratio, according to the following equation: @example @var{DAR} = @var{HORIZONTAL_RESOLUTION} / @var{VERTICAL_RESOLUTION} * @var{SAR} @end example Keep in mind that the @code{setdar} filter does not modify the pixel dimensions of the video frame. Also the display aspect ratio set by this filter may be changed by later filters in the filterchain, e.g. in case of scaling or if another "setdar" or a "setsar" filter is applied. The @code{setsar} filter sets the Sample (aka Pixel) Aspect Ratio for the filter output video. Note that as a consequence of the application of this filter, the output display aspect ratio will change according to the equation above. Keep in mind that the sample aspect ratio set by the @code{setsar} filter may be changed by later filters in the filterchain, e.g. if another "setsar" or a "setdar" filter is applied. The @code{setdar} and @code{setsar} filters accept a string in the form @var{num}:@var{den} expressing an aspect ratio, or the following named options, expressed as a sequence of @var{key}=@var{value} pairs, separated by ":". @table @option @item max Set the maximum integer value to use for expressing numerator and denominator when reducing the expressed aspect ratio to a rational. Default value is @code{100}. @item r, ratio: Set the aspect ratio used by the filter. The parameter can be a floating point number string, an expression, or a string of the form @var{num}:@var{den}, where @var{num} and @var{den} are the numerator and denominator of the aspect ratio. If the parameter is not specified, it is assumed the value "0". In case the form "@var{num}:@var{den}" the @code{:} character should be escaped. @end table If the keys are omitted in the named options list, the specifed values are assumed to be @var{ratio} and @var{max} in that order. For example to change the display aspect ratio to 16:9, specify: @example setdar='16:9' @end example The example above is equivalent to: @example setdar=1.77777 @end example To change the sample aspect ratio to 10:11, specify: @example setsar='10:11' @end example To set a display aspect ratio of 16:9, and specify a maximum integer value of 1000 in the aspect ratio reduction, use the command: @example setdar=ratio='16:9':max=1000 @end example @section setfield Force field for the output video frame. The @code{setfield} filter marks the interlace type field for the output frames. It does not change the input frame, but only sets the corresponding property, which affects how the frame is treated by following filters (e.g. @code{fieldorder} or @code{yadif}). This filter accepts a single option @option{mode}, which can be specified either by setting @code{mode=VALUE} or setting the value alone. Available values are: @table @samp @item auto Keep the same field property. @item bff Mark the frame as bottom-field-first. @item tff Mark the frame as top-field-first. @item prog Mark the frame as progressive. @end table @section showinfo Show a line containing various information for each input video frame. The input video is not modified. The shown line contains a sequence of key/value pairs of the form @var{key}:@var{value}. A description of each shown parameter follows: @table @option @item n sequential number of the input frame, starting from 0 @item pts Presentation TimeStamp of the input frame, expressed as a number of time base units. The time base unit depends on the filter input pad. @item pts_time Presentation TimeStamp of the input frame, expressed as a number of seconds @item pos position of the frame in the input stream, -1 if this information in unavailable and/or meaningless (for example in case of synthetic video) @item fmt pixel format name @item sar sample aspect ratio of the input frame, expressed in the form @var{num}/@var{den} @item s size of the input frame, expressed in the form @var{width}x@var{height} @item i interlaced mode ("P" for "progressive", "T" for top field first, "B" for bottom field first) @item iskey 1 if the frame is a key frame, 0 otherwise @item type picture type of the input frame ("I" for an I-frame, "P" for a P-frame, "B" for a B-frame, "?" for unknown type). Check also the documentation of the @code{AVPictureType} enum and of the @code{av_get_picture_type_char} function defined in @file{libavutil/avutil.h}. @item checksum Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame @item plane_checksum Adler-32 checksum (printed in hexadecimal) of each plane of the input frame, expressed in the form "[@var{c0} @var{c1} @var{c2} @var{c3}]" @end table @section smartblur Blur the input video without impacting the outlines. The filter accepts the following parameters: @var{luma_radius}:@var{luma_strength}:@var{luma_threshold}[:@var{chroma_radius}:@var{chroma_strength}:@var{chroma_threshold}] Parameters prefixed by @var{luma} indicate that they work on the luminance of the pixels whereas parameters prefixed by @var{chroma} refer to the chrominance of the pixels. If the chroma parameters are not set, the luma parameters are used for either the luminance and the chrominance of the pixels. @var{luma_radius} or @var{chroma_radius} must be a float number in the range [0.1,5.0] that specifies the variance of the gaussian filter used to blur the image (slower if larger). @var{luma_strength} or @var{chroma_strength} must be a float number in the range [-1.0,1.0] that configures the blurring. A value included in [0.0,1.0] will blur the image whereas a value included in [-1.0,0.0] will sharpen the image. @var{luma_threshold} or @var{chroma_threshold} must be an integer in the range [-30,30] that is used as a coefficient to determine whether a pixel should be blurred or not. A value of 0 will filter all the image, a value included in [0,30] will filter flat areas and a value included in [-30,0] will filter edges. @anchor{subtitles} @section subtitles Draw subtitles on top of input video using the libass library. To enable compilation of this filter you need to configure FFmpeg with @code{--enable-libass}. This filter also requires a build with libavcodec and libavformat to convert the passed subtitles file to ASS (Advanced Substation Alpha) subtitles format. This filter accepts the following named options, expressed as a sequence of @var{key}=@var{value} pairs, separated by ":". @table @option @item filename, f Set the filename of the subtitle file to read. It must be specified. @item original_size Specify the size of the original video, the video for which the ASS file was composed. Due to a misdesign in ASS aspect ratio arithmetic, this is necessary to correctly scale the fonts if the aspect ratio has been changed. @end table If the first key is not specified, it is assumed that the first value specifies the @option{filename}. For example, to render the file @file{sub.srt} on top of the input video, use the command: @example subtitles=sub.srt @end example which is equivalent to: @example subtitles=filename=sub.srt @end example @section split Split input video into several identical outputs. The filter accepts a single parameter which specifies the number of outputs. If unspecified, it defaults to 2. For example @example ffmpeg -i INPUT -filter_complex split=5 OUTPUT @end example will create 5 copies of the input video. For example: @example [in] split [splitout1][splitout2]; [splitout1] crop=100:100:0:0 [cropout]; [splitout2] pad=200:200:100:100 [padout]; @end example will create two separate outputs from the same input, one cropped and one padded. @section super2xsai Scale the input by 2x and smooth using the Super2xSaI (Scale and Interpolate) pixel art scaling algorithm. Useful for enlarging pixel art images without reducing sharpness. @section swapuv Swap U & V plane. @section thumbnail Select the most representative frame in a given sequence of consecutive frames. It accepts as argument the frames batch size to analyze (default @var{N}=100); in a set of @var{N} frames, the filter will pick one of them, and then handle the next batch of @var{N} frames until the end. Since the filter keeps track of the whole frames sequence, a bigger @var{N} value will result in a higher memory usage, so a high value is not recommended. The following example extract one picture each 50 frames: @example thumbnail=50 @end example Complete example of a thumbnail creation with @command{ffmpeg}: @example ffmpeg -i in.avi -vf thumbnail,scale=300:200 -frames:v 1 out.png @end example @section tile Tile several successive frames together. It accepts a list of options in the form of @var{key}=@var{value} pairs separated by ":". A description of the accepted options follows. @table @option @item layout Set the grid size (i.e. the number of lines and columns) in the form "@var{w}x@var{h}". @item margin Set the outer border margin in pixels. @item padding Set the inner border thickness (i.e. the number of pixels between frames). For more advanced padding options (such as having different values for the edges), refer to the pad video filter. @item nb_frames Set the maximum number of frames to render in the given area. It must be less than or equal to @var{w}x@var{h}. The default value is @code{0}, meaning all the area will be used. @end table Alternatively, the options can be specified as a flat string: @var{layout}[:@var{nb_frames}[:@var{margin}[:@var{padding}]]] For example, produce 8×8 PNG tiles of all keyframes (@option{-skip_frame nokey}) in a movie: @example ffmpeg -skip_frame nokey -i file.avi -vf 'scale=128:72,tile=8x8' -an -vsync 0 keyframes%03d.png @end example The @option{-vsync 0} is necessary to prevent @command{ffmpeg} from duplicating each output frame to accomodate the originally detected frame rate. Another example to display @code{5} pictures in an area of @code{3x2} frames, with @code{7} pixels between them, and @code{2} pixels of initial margin, using mixed flat and named options: @example tile=3x2:nb_frames=5:padding=7:margin=2 @end example @section tinterlace Perform various types of temporal field interlacing. Frames are counted starting from 1, so the first input frame is considered odd. This filter accepts a single option @option{mode} specifying the mode, which can be specified either by specyfing @code{mode=VALUE} either specifying the value alone. Available values are: @table @samp @item merge, 0 Move odd frames into the upper field, even into the lower field, generating a double height frame at half framerate. @item drop_odd, 1 Only output even frames, odd frames are dropped, generating a frame with unchanged height at half framerate. @item drop_even, 2 Only output odd frames, even frames are dropped, generating a frame with unchanged height at half framerate. @item pad, 3 Expand each frame to full height, but pad alternate lines with black, generating a frame with double height at the same input framerate. @item interleave_top, 4 Interleave the upper field from odd frames with the lower field from even frames, generating a frame with unchanged height at half framerate. @item interleave_bottom, 5 Interleave the lower field from odd frames with the upper field from even frames, generating a frame with unchanged height at half framerate. @item interlacex2, 6 Double frame rate with unchanged height. Frames are inserted each containing the second temporal field from the previous input frame and the first temporal field from the next input frame. This mode relies on the top_field_first flag. Useful for interlaced video displays with no field synchronisation. @end table Numeric values are deprecated but are accepted for backward compatibility reasons. Default mode is @code{merge}. @section transpose Transpose rows with columns in the input video and optionally flip it. This filter accepts the following named parameters: @table @option @item dir Specify the transposition direction. Can assume the following values: @table @samp @item 0, 4 Rotate by 90 degrees counterclockwise and vertically flip (default), that is: @example L.R L.l . . -> . . l.r R.r @end example @item 1, 5 Rotate by 90 degrees clockwise, that is: @example L.R l.L . . -> . . l.r r.R @end example @item 2, 6 Rotate by 90 degrees counterclockwise, that is: @example L.R R.r . . -> . . l.r L.l @end example @item 3, 7 Rotate by 90 degrees clockwise and vertically flip, that is: @example L.R r.R . . -> . . l.r l.L @end example @end table For values between 4-7, the transposition is only done if the input video geometry is portrait and not landscape. These values are deprecated, the @code{passthrough} option should be used instead. @item passthrough Do not apply the transposition if the input geometry matches the one specified by the specified value. It accepts the following values: @table @samp @item none Always apply transposition. @item portrait Preserve portrait geometry (when @var{height} >= @var{width}). @item landscape Preserve landscape geometry (when @var{width} >= @var{height}). @end table Default value is @code{none}. @end table @section unsharp Sharpen or blur the input video. It accepts the following parameters: @var{luma_msize_x}:@var{luma_msize_y}:@var{luma_amount}:@var{chroma_msize_x}:@var{chroma_msize_y}:@var{chroma_amount} Negative values for the amount will blur the input video, while positive values will sharpen. All parameters are optional and default to the equivalent of the string '5:5:1.0:5:5:0.0'. @table @option @item luma_msize_x Set the luma matrix horizontal size. It can be an integer between 3 and 13, default value is 5. @item luma_msize_y Set the luma matrix vertical size. It can be an integer between 3 and 13, default value is 5. @item luma_amount Set the luma effect strength. It can be a float number between -2.0 and 5.0, default value is 1.0. @item chroma_msize_x Set the chroma matrix horizontal size. It can be an integer between 3 and 13, default value is 5. @item chroma_msize_y Set the chroma matrix vertical size. It can be an integer between 3 and 13, default value is 5. @item chroma_amount Set the chroma effect strength. It can be a float number between -2.0 and 5.0, default value is 0.0. @end table @example # Strong luma sharpen effect parameters unsharp=7:7:2.5 # Strong blur of both luma and chroma parameters unsharp=7:7:-2:7:7:-2 # Use the default values with @command{ffmpeg} ffmpeg -i in.avi -vf "unsharp" out.mp4 @end example @section vflip Flip the input video vertically. @example ffmpeg -i in.avi -vf "vflip" out.avi @end example @section yadif Deinterlace the input video ("yadif" means "yet another deinterlacing filter"). It accepts the optional parameters: @var{mode}:@var{parity}:@var{auto}. @var{mode} specifies the interlacing mode to adopt, accepts one of the following values: @table @option @item 0 output 1 frame for each frame @item 1 output 1 frame for each field @item 2 like 0 but skips spatial interlacing check @item 3 like 1 but skips spatial interlacing check @end table Default value is 0. @var{parity} specifies the picture field parity assumed for the input interlaced video, accepts one of the following values: @table @option @item 0 assume top field first @item 1 assume bottom field first @item -1 enable automatic detection @end table Default value is -1. If interlacing is unknown or decoder does not export this information, top field first will be assumed. @var{auto} specifies if deinterlacer should trust the interlaced flag and only deinterlace frames marked as interlaced @table @option @item 0 deinterlace all frames @item 1 only deinterlace frames marked as interlaced @end table Default value is 0. @c man end VIDEO FILTERS @chapter Video Sources @c man begin VIDEO SOURCES Below is a description of the currently available video sources. @section buffer Buffer video frames, and make them available to the filter chain. This source is mainly intended for a programmatic use, in particular through the interface defined in @file{libavfilter/vsrc_buffer.h}. It accepts a list of options in the form of @var{key}=@var{value} pairs separated by ":". A description of the accepted options follows. @table @option @item video_size Specify the size (width and height) of the buffered video frames. @item pix_fmt A string representing the pixel format of the buffered video frames. It may be a number corresponding to a pixel format, or a pixel format name. @item time_base Specify the timebase assumed by the timestamps of the buffered frames. @item time_base Specify the frame rate expected for the video stream. @item pixel_aspect Specify the sample aspect ratio assumed by the video frames. @item sws_param Specify the optional parameters to be used for the scale filter which is automatically inserted when an input change is detected in the input size or format. @end table For example: @example buffer=size=320x240:pix_fmt=yuv410p:time_base=1/24:pixel_aspect=1/1 @end example will instruct the source to accept video frames with size 320x240 and with format "yuv410p", assuming 1/24 as the timestamps timebase and square pixels (1:1 sample aspect ratio). Since the pixel format with name "yuv410p" corresponds to the number 6 (check the enum AVPixelFormat definition in @file{libavutil/pixfmt.h}), this example corresponds to: @example buffer=size=320x240:pixfmt=6:time_base=1/24:pixel_aspect=1/1 @end example Alternatively, the options can be specified as a flat string, but this syntax is deprecated: @var{width}:@var{height}:@var{pix_fmt}:@var{time_base.num}:@var{time_base.den}:@var{pixel_aspect.num}:@var{pixel_aspect.den}[:@var{sws_param}] @section cellauto Create a pattern generated by an elementary cellular automaton. The initial state of the cellular automaton can be defined through the @option{filename}, and @option{pattern} options. If such options are not specified an initial state is created randomly. At each new frame a new row in the video is filled with the result of the cellular automaton next generation. The behavior when the whole frame is filled is defined by the @option{scroll} option. This source accepts a list of options in the form of @var{key}=@var{value} pairs separated by ":". A description of the accepted options follows. @table @option @item filename, f Read the initial cellular automaton state, i.e. the starting row, from the specified file. In the file, each non-whitespace character is considered an alive cell, a newline will terminate the row, and further characters in the file will be ignored. @item pattern, p Read the initial cellular automaton state, i.e. the starting row, from the specified string. Each non-whitespace character in the string is considered an alive cell, a newline will terminate the row, and further characters in the string will be ignored. @item rate, r Set the video rate, that is the number of frames generated per second. Default is 25. @item random_fill_ratio, ratio Set the random fill ratio for the initial cellular automaton row. It is a floating point number value ranging from 0 to 1, defaults to 1/PHI. This option is ignored when a file or a pattern is specified. @item random_seed, seed Set the seed for filling randomly the initial row, must be an integer included between 0 and UINT32_MAX. If not specified, or if explicitly set to -1, the filter will try to use a good random seed on a best effort basis. @item rule Set the cellular automaton rule, it is a number ranging from 0 to 255. Default value is 110. @item size, s Set the size of the output video. If @option{filename} or @option{pattern} is specified, the size is set by default to the width of the specified initial state row, and the height is set to @var{width} * PHI. If @option{size} is set, it must contain the width of the specified pattern string, and the specified pattern will be centered in the larger row. If a filename or a pattern string is not specified, the size value defaults to "320x518" (used for a randomly generated initial state). @item scroll If set to 1, scroll the output upward when all the rows in the output have been already filled. If set to 0, the new generated row will be written over the top row just after the bottom row is filled. Defaults to 1. @item start_full, full If set to 1, completely fill the output with generated rows before outputting the first frame. This is the default behavior, for disabling set the value to 0. @item stitch If set to 1, stitch the left and right row edges together. This is the default behavior, for disabling set the value to 0. @end table @subsection Examples @itemize @item Read the initial state from @file{pattern}, and specify an output of size 200x400. @example cellauto=f=pattern:s=200x400 @end example @item Generate a random initial row with a width of 200 cells, with a fill ratio of 2/3: @example cellauto=ratio=2/3:s=200x200 @end example @item Create a pattern generated by rule 18 starting by a single alive cell centered on an initial row with width 100: @example cellauto=p=@@:s=100x400:full=0:rule=18 @end example @item Specify a more elaborated initial pattern: @example cellauto=p='@@@@ @@ @@@@':s=100x400:full=0:rule=18 @end example @end itemize @section mandelbrot Generate a Mandelbrot set fractal, and progressively zoom towards the point specified with @var{start_x} and @var{start_y}. This source accepts a list of options in the form of @var{key}=@var{value} pairs separated by ":". A description of the accepted options follows. @table @option @item end_pts Set the terminal pts value. Default value is 400. @item end_scale Set the terminal scale value. Must be a floating point value. Default value is 0.3. @item inner Set the inner coloring mode, that is the algorithm used to draw the Mandelbrot fractal internal region. It shall assume one of the following values: @table @option @item black Set black mode. @item convergence Show time until convergence. @item mincol Set color based on point closest to the origin of the iterations. @item period Set period mode. @end table Default value is @var{mincol}. @item bailout Set the bailout value. Default value is 10.0. @item maxiter Set the maximum of iterations performed by the rendering algorithm. Default value is 7189. @item outer Set outer coloring mode. It shall assume one of following values: @table @option @item iteration_count Set iteration cound mode. @item normalized_iteration_count set normalized iteration count mode. @end table Default value is @var{normalized_iteration_count}. @item rate, r Set frame rate, expressed as number of frames per second. Default value is "25". @item size, s Set frame size. Default value is "640x480". @item start_scale Set the initial scale value. Default value is 3.0. @item start_x Set the initial x position. Must be a floating point value between -100 and 100. Default value is -0.743643887037158704752191506114774. @item start_y Set the initial y position. Must be a floating point value between -100 and 100. Default value is -0.131825904205311970493132056385139. @end table @section mptestsrc Generate various test patterns, as generated by the MPlayer test filter. The size of the generated video is fixed, and is 256x256. This source is useful in particular for testing encoding features. This source accepts an optional sequence of @var{key}=@var{value} pairs, separated by ":". The description of the accepted options follows. @table @option @item rate, r Specify the frame rate of the sourced video, as the number of frames generated per second. It has to be a string in the format @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float number or a valid video frame rate abbreviation. The default value is "25". @item duration, d Set the video duration of the sourced video. The accepted syntax is: @example [-]HH:MM:SS[.m...] [-]S+[.m...] @end example See also the function @code{av_parse_time()}. If not specified, or the expressed duration is negative, the video is supposed to be generated forever. @item test, t Set the number or the name of the test to perform. Supported tests are: @table @option @item dc_luma @item dc_chroma @item freq_luma @item freq_chroma @item amp_luma @item amp_chroma @item cbp @item mv @item ring1 @item ring2 @item all @end table Default value is "all", which will cycle through the list of all tests. @end table For example the following: @example testsrc=t=dc_luma @end example will generate a "dc_luma" test pattern. @section frei0r_src Provide a frei0r source. To enable compilation of this filter you need to install the frei0r header and configure FFmpeg with @code{--enable-frei0r}. The source supports the syntax: @example @var{size}:@var{rate}:@var{src_name}[@{=|:@}@var{param1}:@var{param2}:...:@var{paramN}] @end example @var{size} is the size of the video to generate, may be a string of the form @var{width}x@var{height} or a frame size abbreviation. @var{rate} is the rate of the video to generate, may be a string of the form @var{num}/@var{den} or a frame rate abbreviation. @var{src_name} is the name to the frei0r source to load. For more information regarding frei0r and how to set the parameters read the section @ref{frei0r} in the description of the video filters. For example, to generate a frei0r partik0l source with size 200x200 and frame rate 10 which is overlayed on the overlay filter main input: @example frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay @end example @section life Generate a life pattern. This source is based on a generalization of John Conway's life game. The sourced input represents a life grid, each pixel represents a cell which can be in one of two possible states, alive or dead. Every cell interacts with its eight neighbours, which are the cells that are horizontally, vertically, or diagonally adjacent. At each interaction the grid evolves according to the adopted rule, which specifies the number of neighbor alive cells which will make a cell stay alive or born. The @option{rule} option allows to specify the rule to adopt. This source accepts a list of options in the form of @var{key}=@var{value} pairs separated by ":". A description of the accepted options follows. @table @option @item filename, f Set the file from which to read the initial grid state. In the file, each non-whitespace character is considered an alive cell, and newline is used to delimit the end of each row. If this option is not specified, the initial grid is generated randomly. @item rate, r Set the video rate, that is the number of frames generated per second. Default is 25. @item random_fill_ratio, ratio Set the random fill ratio for the initial random grid. It is a floating point number value ranging from 0 to 1, defaults to 1/PHI. It is ignored when a file is specified. @item random_seed, seed Set the seed for filling the initial random grid, must be an integer included between 0 and UINT32_MAX. If not specified, or if explicitly set to -1, the filter will try to use a good random seed on a best effort basis. @item rule Set the life rule. A rule can be specified with a code of the kind "S@var{NS}/B@var{NB}", where @var{NS} and @var{NB} are sequences of numbers in the range 0-8, @var{NS} specifies the number of alive neighbor cells which make a live cell stay alive, and @var{NB} the number of alive neighbor cells which make a dead cell to become alive (i.e. to "born"). "s" and "b" can be used in place of "S" and "B", respectively. Alternatively a rule can be specified by an 18-bits integer. The 9 high order bits are used to encode the next cell state if it is alive for each number of neighbor alive cells, the low order bits specify the rule for "borning" new cells. Higher order bits encode for an higher number of neighbor cells. For example the number 6153 = @code{(12<<9)+9} specifies a stay alive rule of 12 and a born rule of 9, which corresponds to "S23/B03". Default value is "S23/B3", which is the original Conway's game of life rule, and will keep a cell alive if it has 2 or 3 neighbor alive cells, and will born a new cell if there are three alive cells around a dead cell. @item size, s Set the size of the output video. If @option{filename} is specified, the size is set by default to the same size of the input file. If @option{size} is set, it must contain the size specified in the input file, and the initial grid defined in that file is centered in the larger resulting area. If a filename is not specified, the size value defaults to "320x240" (used for a randomly generated initial grid). @item stitch If set to 1, stitch the left and right grid edges together, and the top and bottom edges also. Defaults to 1. @item mold Set cell mold speed. If set, a dead cell will go from @option{death_color} to @option{mold_color} with a step of @option{mold}. @option{mold} can have a value from 0 to 255. @item life_color Set the color of living (or new born) cells. @item death_color Set the color of dead cells. If @option{mold} is set, this is the first color used to represent a dead cell. @item mold_color Set mold color, for definitely dead and moldy cells. @end table @subsection Examples @itemize @item Read a grid from @file{pattern}, and center it on a grid of size 300x300 pixels: @example life=f=pattern:s=300x300 @end example @item Generate a random grid of size 200x200, with a fill ratio of 2/3: @example life=ratio=2/3:s=200x200 @end example @item Specify a custom rule for evolving a randomly generated grid: @example life=rule=S14/B34 @end example @item Full example with slow death effect (mold) using @command{ffplay}: @example ffplay -f lavfi life=s=300x200:mold=10:r=60:ratio=0.1:death_color=#C83232:life_color=#00ff00,scale=1200:800:flags=16 @end example @end itemize @section color, nullsrc, rgbtestsrc, smptebars, testsrc The @code{color} source provides an uniformly colored input. The @code{nullsrc} source returns unprocessed video frames. It is mainly useful to be employed in analysis / debugging tools, or as the source for filters which ignore the input data. The @code{rgbtestsrc} source generates an RGB test pattern useful for detecting RGB vs BGR issues. You should see a red, green and blue stripe from top to bottom. The @code{smptebars} source generates a color bars pattern, based on the SMPTE Engineering Guideline EG 1-1990. The @code{testsrc} source generates a test video pattern, showing a color pattern, a scrolling gradient and a timestamp. This is mainly intended for testing purposes. These sources accept an optional sequence of @var{key}=@var{value} pairs, separated by ":". The description of the accepted options follows. @table @option @item color, c Specify the color of the source, only used in the @code{color} source. It can be the name of a color (case insensitive match) or a 0xRRGGBB[AA] sequence, possibly followed by an alpha specifier. The default value is "black". @item size, s Specify the size of the sourced video, it may be a string of the form @var{width}x@var{height}, or the name of a size abbreviation. The default value is "320x240". @item rate, r Specify the frame rate of the sourced video, as the number of frames generated per second. It has to be a string in the format @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float number or a valid video frame rate abbreviation. The default value is "25". @item sar Set the sample aspect ratio of the sourced video. @item duration, d Set the video duration of the sourced video. The accepted syntax is: @example [-]HH[:MM[:SS[.m...]]] [-]S+[.m...] @end example See also the function @code{av_parse_time()}. If not specified, or the expressed duration is negative, the video is supposed to be generated forever. @item decimals, n Set the number of decimals to show in the timestamp, only used in the @code{testsrc} source. The displayed timestamp value will correspond to the original timestamp value multiplied by the power of 10 of the specified value. Default value is 0. @end table For example the following: @example testsrc=duration=5.3:size=qcif:rate=10 @end example will generate a video with a duration of 5.3 seconds, with size 176x144 and a frame rate of 10 frames per second. The following graph description will generate a red source with an opacity of 0.2, with size "qcif" and a frame rate of 10 frames per second. @example color=c=red@@0.2:s=qcif:r=10 @end example If the input content is to be ignored, @code{nullsrc} can be used. The following command generates noise in the luminance plane by employing the @code{geq} filter: @example nullsrc=s=256x256, geq=random(1)*255:128:128 @end example @c man end VIDEO SOURCES @chapter Video Sinks @c man begin VIDEO SINKS Below is a description of the currently available video sinks. @section buffersink Buffer video frames, and make them available to the end of the filter graph. This sink is mainly intended for a programmatic use, in particular through the interface defined in @file{libavfilter/buffersink.h}. It does not require a string parameter in input, but you need to specify a pointer to a list of supported pixel formats terminated by -1 in the opaque parameter provided to @code{avfilter_init_filter} when initializing this sink. @section nullsink Null video sink, do absolutely nothing with the input video. It is mainly useful as a template and to be employed in analysis / debugging tools. @c man end VIDEO SINKS @chapter Multimedia Filters @c man begin MULTIMEDIA FILTERS Below is a description of the currently available multimedia filters. @section aselect, select Select frames to pass in output. These filters accept a single option @option{expr} or @option{e} specifying the select expression, which can be specified either by specyfing @code{expr=VALUE} or specifying the expression alone. The select expression is evaluated for each input frame. If the evaluation result is a non-zero value, the frame is selected and passed to the output, otherwise it is discarded. The expression can contain the following constants: @table @option @item n the sequential number of the filtered frame, starting from 0 @item selected_n the sequential number of the selected frame, starting from 0 @item prev_selected_n the sequential number of the last selected frame, NAN if undefined @item TB timebase of the input timestamps @item pts the PTS (Presentation TimeStamp) of the filtered video frame, expressed in @var{TB} units, NAN if undefined @item t the PTS (Presentation TimeStamp) of the filtered video frame, expressed in seconds, NAN if undefined @item prev_pts the PTS of the previously filtered video frame, NAN if undefined @item prev_selected_pts the PTS of the last previously filtered video frame, NAN if undefined @item prev_selected_t the PTS of the last previously selected video frame, NAN if undefined @item start_pts the PTS of the first video frame in the video, NAN if undefined @item start_t the time of the first video frame in the video, NAN if undefined @item pict_type @emph{(video only)} the type of the filtered frame, can assume one of the following values: @table @option @item I @item P @item B @item S @item SI @item SP @item BI @end table @item interlace_type @emph{(video only)} the frame interlace type, can assume one of the following values: @table @option @item PROGRESSIVE the frame is progressive (not interlaced) @item TOPFIRST the frame is top-field-first @item BOTTOMFIRST the frame is bottom-field-first @end table @item consumed_sample_n @emph{(audio only)} the number of selected samples before the current frame @item samples_n @emph{(audio only)} the number of samples in the current frame @item sample_rate @emph{(audio only)} the input sample rate @item key 1 if the filtered frame is a key-frame, 0 otherwise @item pos the position in the file of the filtered frame, -1 if the information is not available (e.g. for synthetic video) @item scene @emph{(video only)} value between 0 and 1 to indicate a new scene; a low value reflects a low probability for the current frame to introduce a new scene, while a higher value means the current frame is more likely to be one (see the example below) @end table The default value of the select expression is "1". @subsection Examples @itemize @item Select all frames in input: @example select @end example The example above is the same as: @example select=1 @end example @item Skip all frames: @example select=0 @end example @item Select only I-frames: @example select='eq(pict_type\,I)' @end example @item Select one frame every 100: @example select='not(mod(n\,100))' @end example @item Select only frames contained in the 10-20 time interval: @example select='gte(t\,10)*lte(t\,20)' @end example @item Select only I frames contained in the 10-20 time interval: @example select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)' @end example @item Select frames with a minimum distance of 10 seconds: @example select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)' @end example @item Use aselect to select only audio frames with samples number > 100: @example aselect='gt(samples_n\,100)' @end example @item Create a mosaic of the first scenes: @example ffmpeg -i video.avi -vf select='gt(scene\,0.4)',scale=160:120,tile -frames:v 1 preview.png @end example Comparing @var{scene} against a value between 0.3 and 0.5 is generally a sane choice. @end itemize @section asendcmd, sendcmd Send commands to filters in the filtergraph. These filters read commands to be sent to other filters in the filtergraph. @code{asendcmd} must be inserted between two audio filters, @code{sendcmd} must be inserted between two video filters, but apart from that they act the same way. The specification of commands can be provided in the filter arguments with the @var{commands} option, or in a file specified by the @var{filename} option. These filters accept the following options: @table @option @item commands, c Set the commands to be read and sent to the other filters. @item filename, f Set the filename of the commands to be read and sent to the other filters. @end table @subsection Commands syntax A commands description consists of a sequence of interval specifications, comprising a list of commands to be executed when a particular event related to that interval occurs. The occurring event is typically the current frame time entering or leaving a given time interval. An interval is specified by the following syntax: @example @var{START}[-@var{END}] @var{COMMANDS}; @end example The time interval is specified by the @var{START} and @var{END} times. @var{END} is optional and defaults to the maximum time. The current frame time is considered within the specified interval if it is included in the interval [@var{START}, @var{END}), that is when the time is greater or equal to @var{START} and is lesser than @var{END}. @var{COMMANDS} consists of a sequence of one or more command specifications, separated by ",", relating to that interval. The syntax of a command specification is given by: @example [@var{FLAGS}] @var{TARGET} @var{COMMAND} @var{ARG} @end example @var{FLAGS} is optional and specifies the type of events relating to the time interval which enable sending the specified command, and must be a non-null sequence of identifier flags separated by "+" or "|" and enclosed between "[" and "]". The following flags are recognized: @table @option @item enter The command is sent when the current frame timestamp enters the specified interval. In other words, the command is sent when the previous frame timestamp was not in the given interval, and the current is. @item leave The command is sent when the current frame timestamp leaves the specified interval. In other words, the command is sent when the previous frame timestamp was in the given interval, and the current is not. @end table If @var{FLAGS} is not specified, a default value of @code{[enter]} is assumed. @var{TARGET} specifies the target of the command, usually the name of the filter class or a specific filter instance name. @var{COMMAND} specifies the name of the command for the target filter. @var{ARG} is optional and specifies the optional list of argument for the given @var{COMMAND}. Between one interval specification and another, whitespaces, or sequences of characters starting with @code{#} until the end of line, are ignored and can be used to annotate comments. A simplified BNF description of the commands specification syntax follows: @example @var{COMMAND_FLAG} ::= "enter" | "leave" @var{COMMAND_FLAGS} ::= @var{COMMAND_FLAG} [(+|"|")@var{COMMAND_FLAG}] @var{COMMAND} ::= ["[" @var{COMMAND_FLAGS} "]"] @var{TARGET} @var{COMMAND} [@var{ARG}] @var{COMMANDS} ::= @var{COMMAND} [,@var{COMMANDS}] @var{INTERVAL} ::= @var{START}[-@var{END}] @var{COMMANDS} @var{INTERVALS} ::= @var{INTERVAL}[;@var{INTERVALS}] @end example @subsection Examples @itemize @item Specify audio tempo change at second 4: @example asendcmd=c='4.0 atempo tempo 1.5',atempo @end example @item Specify a list of drawtext and hue commands in a file. @example # show text in the interval 5-10 5.0-10.0 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=hello world', [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text='; # desaturate the image in the interval 15-20 15.0-20.0 [enter] hue reinit s=0, [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=nocolor', [leave] hue reinit s=1, [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=color'; # apply an exponential saturation fade-out effect, starting from time 25 25 [enter] hue s=exp(t-25) @end example A filtergraph allowing to read and process the above command list stored in a file @file{test.cmd}, can be specified with: @example sendcmd=f=test.cmd,drawtext=fontfile=FreeSerif.ttf:text='',hue @end example @end itemize @anchor{setpts} @section asetpts, setpts Change the PTS (presentation timestamp) of the input frames. @code{asetpts} works on audio frames, @code{setpts} on video frames. Accept in input an expression evaluated through the eval API, which can contain the following constants: @table @option @item FRAME_RATE frame rate, only defined for constant frame-rate video @item PTS the presentation timestamp in input @item N the count of the input frame, starting from 0. @item NB_CONSUMED_SAMPLES the number of consumed samples, not including the current frame (only audio) @item NB_SAMPLES the number of samples in the current frame (only audio) @item SAMPLE_RATE audio sample rate @item STARTPTS the PTS of the first frame @item STARTT the time in seconds of the first frame @item INTERLACED tell if the current frame is interlaced @item T the time in seconds of the current frame @item TB the time base @item POS original position in the file of the frame, or undefined if undefined for the current frame @item PREV_INPTS previous input PTS @item PREV_INT previous input time in seconds @item PREV_OUTPTS previous output PTS @item PREV_OUTT previous output time in seconds @end table @subsection Examples @itemize @item Start counting PTS from zero @example setpts=PTS-STARTPTS @end example @item Apply fast motion effect: @example setpts=0.5*PTS @end example @item Apply slow motion effect: @example setpts=2.0*PTS @end example @item Set fixed rate of 25 frames per second: @example setpts=N/(25*TB) @end example @item Set fixed rate 25 fps with some jitter: @example setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))' @end example @item Apply an offset of 10 seconds to the input PTS: @example setpts=PTS+10/TB @end example @end itemize @section ebur128 EBU R128 scanner filter. This filter takes an audio stream as input and outputs it unchanged. By default, it logs a message at a frequency of 10Hz with the Momentary loudness (identified by @code{M}), Short-term loudness (@code{S}), Integrated loudness (@code{I}) and Loudness Range (@code{LRA}). The filter also has a video output (see the @var{video} option) with a real time graph to observe the loudness evolution. The graphic contains the logged message mentioned above, so it is not printed anymore when this option is set, unless the verbose logging is set. The main graphing area contains the short-term loudness (3 seconds of analysis), and the gauge on the right is for the momentary loudness (400 milliseconds). More information about the Loudness Recommendation EBU R128 on @url{http://tech.ebu.ch/loudness}. The filter accepts the following named parameters: @table @option @item video Activate the video output. The audio stream is passed unchanged whether this option is set or no. The video stream will be the first output stream if activated. Default is @code{0}. @item size Set the video size. This option is for video only. Default and minimum resolution is @code{640x480}. @item meter Set the EBU scale meter. Default is @code{9}. Common values are @code{9} and @code{18}, respectively for EBU scale meter +9 and EBU scale meter +18. Any other integer value between this range is allowed. @end table Example of real-time graph using @command{ffplay}, with a EBU scale meter +18: @example ffplay -f lavfi -i "amovie=input.mp3,ebur128=video=1:meter=18 [out0][out1]" @end example Run an analysis with @command{ffmpeg}: @example ffmpeg -nostats -i input.mp3 -filter_complex ebur128 -f null - @end example @section settb, asettb Set the timebase to use for the output frames timestamps. It is mainly useful for testing timebase configuration. It accepts in input an arithmetic expression representing a rational. The expression can contain the constants "AVTB" (the default timebase), "intb" (the input timebase) and "sr" (the sample rate, audio only). The default value for the input is "intb". @subsection Examples @itemize @item Set the timebase to 1/25: @example settb=1/25 @end example @item Set the timebase to 1/10: @example settb=0.1 @end example @item Set the timebase to 1001/1000: @example settb=1+0.001 @end example @item Set the timebase to 2*intb: @example settb=2*intb @end example @item Set the default timebase value: @example settb=AVTB @end example @end itemize @section concat Concatenate audio and video streams, joining them together one after the other. The filter works on segments of synchronized video and audio streams. All segments must have the same number of streams of each type, and that will also be the number of streams at output. The filter accepts the following named parameters: @table @option @item n Set the number of segments. Default is 2. @item v Set the number of output video streams, that is also the number of video streams in each segment. Default is 1. @item a Set the number of output audio streams, that is also the number of video streams in each segment. Default is 0. @item unsafe Activate unsafe mode: do not fail if segments have a different format. @end table The filter has @var{v}+@var{a} outputs: first @var{v} video outputs, then @var{a} audio outputs. There are @var{n}×(@var{v}+@var{a}) inputs: first the inputs for the first segment, in the same order as the outputs, then the inputs for the second segment, etc. Related streams do not always have exactly the same duration, for various reasons including codec frame size or sloppy authoring. For that reason, related synchronized streams (e.g. a video and its audio track) should be concatenated at once. The concat filter will use the duration of the longest stream in each segment (except the last one), and if necessary pad shorter audio streams with silence. For this filter to work correctly, all segments must start at timestamp 0. All corresponding streams must have the same parameters in all segments; the filtering system will automatically select a common pixel format for video streams, and a common sample format, sample rate and channel layout for audio streams, but other settings, such as resolution, must be converted explicitly by the user. Different frame rates are acceptable but will result in variable frame rate at output; be sure to configure the output file to handle it. Examples: @itemize @item Concatenate an opening, an episode and an ending, all in bilingual version (video in stream 0, audio in streams 1 and 2): @example ffmpeg -i opening.mkv -i episode.mkv -i ending.mkv -filter_complex \ '[0:0] [0:1] [0:2] [1:0] [1:1] [1:2] [2:0] [2:1] [2:2] concat=n=3:v=1:a=2 [v] [a1] [a2]' \ -map '[v]' -map '[a1]' -map '[a2]' output.mkv @end example @item Concatenate two parts, handling audio and video separately, using the (a)movie sources, and adjusting the resolution: @example movie=part1.mp4, scale=512:288 [v1] ; amovie=part1.mp4 [a1] ; movie=part2.mp4, scale=512:288 [v2] ; amovie=part2.mp4 [a2] ; [v1] [v2] concat [outv] ; [a1] [a2] concat=v=0:a=1 [outa] @end example Note that a desync will happen at the stitch if the audio and video streams do not have exactly the same duration in the first file. @end itemize @section showspectrum Convert input audio to a video output, representing the audio frequency spectrum. The filter accepts the following named parameters: @table @option @item size, s Specify the video size for the output. Default value is @code{640x480}. @item slide Specify if the spectrum should slide along the window. Default value is @code{0}. @end table The usage is very similar to the showwaves filter; see the examples in that section. @section showwaves Convert input audio to a video output, representing the samples waves. The filter accepts the following named parameters: @table @option @item n Set the number of samples which are printed on the same column. A larger value will decrease the frame rate. Must be a positive integer. This option can be set only if the value for @var{rate} is not explicitly specified. @item rate, r Set the (approximate) output frame rate. This is done by setting the option @var{n}. Default value is "25". @item size, s Specify the video size for the output. Default value is "600x240". @end table Some examples follow. @itemize @item Output the input file audio and the corresponding video representation at the same time: @example amovie=a.mp3,asplit[out0],showwaves[out1] @end example @item Create a synthetic signal and show it with showwaves, forcing a framerate of 30 frames per second: @example aevalsrc=sin(1*2*PI*t)*sin(880*2*PI*t):cos(2*PI*200*t),asplit[out0],showwaves=r=30[out1] @end example @end itemize @c man end MULTIMEDIA FILTERS @chapter Multimedia Sources @c man begin MULTIMEDIA SOURCES Below is a description of the currently available multimedia sources. @section amovie This is the same as @ref{src_movie} source, except it selects an audio stream by default. @anchor{src_movie} @section movie Read audio and/or video stream(s) from a movie container. It accepts the syntax: @var{movie_name}[:@var{options}] where @var{movie_name} is the name of the resource to read (not necessarily a file but also a device or a stream accessed through some protocol), and @var{options} is an optional sequence of @var{key}=@var{value} pairs, separated by ":". The description of the accepted options follows. @table @option @item format_name, f Specifies the format assumed for the movie to read, and can be either the name of a container or an input device. If not specified the format is guessed from @var{movie_name} or by probing. @item seek_point, sp Specifies the seek point in seconds, the frames will be output starting from this seek point, the parameter is evaluated with @code{av_strtod} so the numerical value may be suffixed by an IS postfix. Default value is "0". @item streams, s Specifies the streams to read. Several streams can be specified, separated by "+". The source will then have as many outputs, in the same order. The syntax is explained in the @ref{Stream specifiers} chapter. Two special names, "dv" and "da" specify respectively the default (best suited) video and audio stream. Default is "dv", or "da" if the filter is called as "amovie". @item stream_index, si Specifies the index of the video stream to read. If the value is -1, the best suited video stream will be automatically selected. Default value is "-1". Deprecated. If the filter is called "amovie", it will select audio instead of video. @item loop Specifies how many times to read the stream in sequence. If the value is less than 1, the stream will be read again and again. Default value is "1". Note that when the movie is looped the source timestamps are not changed, so it will generate non monotonically increasing timestamps. @end table This filter allows to overlay a second video on top of main input of a filtergraph as shown in this graph: @example input -----------> deltapts0 --> overlay --> output ^ | movie --> scale--> deltapts1 -------+ @end example Some examples follow. @itemize @item Skip 3.2 seconds from the start of the avi file in.avi, and overlay it on top of the input labelled as "in": @example movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie]; [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out] @end example @item Read from a video4linux2 device, and overlay it on top of the input labelled as "in": @example movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie]; [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out] @end example @item Read the first video stream and the audio stream with id 0x81 from dvd.vob; the video is connected to the pad named "video" and the audio is connected to the pad named "audio": @example movie=dvd.vob:s=v:0+#0x81 [video] [audio] @end example @end itemize @c man end MULTIMEDIA SOURCES