@chapter Decoders @c man begin DECODERS Decoders are configured elements in FFmpeg which allow the decoding of multimedia streams. When you configure your FFmpeg build, all the supported native decoders are enabled by default. Decoders requiring an external library must be enabled manually via the corresponding @code{--enable-lib} option. You can list all available decoders using the configure option @code{--list-decoders}. You can disable all the decoders with the configure option @code{--disable-decoders} and selectively enable / disable single decoders with the options @code{--enable-decoder=@var{DECODER}} / @code{--disable-decoder=@var{DECODER}}. The option @code{-decoders} of the ff* tools will display the list of enabled decoders. @c man end DECODERS @chapter Video Decoders @c man begin VIDEO DECODERS A description of some of the currently available video decoders follows. @section av1 AOMedia Video 1 (AV1) decoder. @subsection Options @table @option @item operating_point Select an operating point of a scalable AV1 bitstream (0 - 31). Default is 0. @end table @section rawvideo Raw video decoder. This decoder decodes rawvideo streams. @subsection Options @table @option @item top @var{top_field_first} Specify the assumed field type of the input video. @table @option @item -1 the video is assumed to be progressive (default) @item 0 bottom-field-first is assumed @item 1 top-field-first is assumed @end table @end table @section libdav1d dav1d AV1 decoder. libdav1d allows libavcodec to decode the AOMedia Video 1 (AV1) codec. Requires the presence of the libdav1d headers and library during configuration. You need to explicitly configure the build with @code{--enable-libdav1d}. @subsection Options The following options are supported by the libdav1d wrapper. @table @option @item framethreads Set amount of frame threads to use during decoding. The default value is 0 (autodetect). This option is deprecated for libdav1d >= 1.0 and will be removed in the future. Use the option @code{max_frame_delay} and the global option @code{threads} instead. @item tilethreads Set amount of tile threads to use during decoding. The default value is 0 (autodetect). This option is deprecated for libdav1d >= 1.0 and will be removed in the future. Use the global option @code{threads} instead. @item max_frame_delay Set max amount of frames the decoder may buffer internally. The default value is 0 (autodetect). @item filmgrain Apply film grain to the decoded video if present in the bitstream. Defaults to the internal default of the library. This option is deprecated and will be removed in the future. See the global option @code{export_side_data} to export Film Grain parameters instead of applying it. @item oppoint Select an operating point of a scalable AV1 bitstream (0 - 31). Defaults to the internal default of the library. @item alllayers Output all spatial layers of a scalable AV1 bitstream. The default value is false. @end table @section libdavs2 AVS2-P2/IEEE1857.4 video decoder wrapper. This decoder allows libavcodec to decode AVS2 streams with davs2 library. @c man end VIDEO DECODERS @section libuavs3d AVS3-P2/IEEE1857.10 video decoder. libuavs3d allows libavcodec to decode AVS3 streams. Requires the presence of the libuavs3d headers and library during configuration. You need to explicitly configure the build with @code{--enable-libuavs3d}. @subsection Options The following option is supported by the libuavs3d wrapper. @table @option @item frame_threads Set amount of frame threads to use during decoding. The default value is 0 (autodetect). @end table @section QSV Decoders The family of Intel QuickSync Video decoders (VC1, MPEG-2, H.264, HEVC, JPEG/MJPEG, VP8, VP9, AV1). @subsection Common Options The following options are supported by all qsv decoders. @table @option @item @var{async_depth} Internal parallelization depth, the higher the value the higher the latency. @item @var{gpu_copy} A GPU-accelerated copy between video and system memory @table @samp @item default @item on @item off @end table @end table @subsection HEVC Options Extra options for hevc_qsv. @table @option @item @var{load_plugin} A user plugin to load in an internal session @table @samp @item none @item hevc_sw @item hevc_hw @end table @item @var{load_plugins} A :-separate list of hexadecimal plugin UIDs to load in an internal session @end table @section v210 Uncompressed 4:2:2 10-bit decoder. @subsection Options @table @option @item custom_stride Set the line size of the v210 data in bytes. The default value is 0 (autodetect). You can use the special -1 value for a strideless v210 as seen in BOXX files. @end table @c man end VIDEO DECODERS @chapter Audio Decoders @c man begin AUDIO DECODERS A description of some of the currently available audio decoders follows. @section ac3 AC-3 audio decoder. This decoder implements part of ATSC A/52:2010 and ETSI TS 102 366, as well as the undocumented RealAudio 3 (a.k.a. dnet). @subsection AC-3 Decoder Options @table @option @item -drc_scale @var{value} Dynamic Range Scale Factor. The factor to apply to dynamic range values from the AC-3 stream. This factor is applied exponentially. The default value is 1. There are 3 notable scale factor ranges: @table @option @item drc_scale == 0 DRC disabled. Produces full range audio. @item 0 < drc_scale <= 1 DRC enabled. Applies a fraction of the stream DRC value. Audio reproduction is between full range and full compression. @item drc_scale > 1 DRC enabled. Applies drc_scale asymmetrically. Loud sounds are fully compressed. Soft sounds are enhanced. @end table @end table @section flac FLAC audio decoder. This decoder aims to implement the complete FLAC specification from Xiph. @subsection FLAC Decoder options @table @option @item -use_buggy_lpc The lavc FLAC encoder used to produce buggy streams with high lpc values (like the default value). This option makes it possible to decode such streams correctly by using lavc's old buggy lpc logic for decoding. @end table @section ffwavesynth Internal wave synthesizer. This decoder generates wave patterns according to predefined sequences. Its use is purely internal and the format of the data it accepts is not publicly documented. @section libcelt libcelt decoder wrapper. libcelt allows libavcodec to decode the Xiph CELT ultra-low delay audio codec. Requires the presence of the libcelt headers and library during configuration. You need to explicitly configure the build with @code{--enable-libcelt}. @section libgsm libgsm decoder wrapper. libgsm allows libavcodec to decode the GSM full rate audio codec. Requires the presence of the libgsm headers and library during configuration. You need to explicitly configure the build with @code{--enable-libgsm}. This decoder supports both the ordinary GSM and the Microsoft variant. @section libilbc libilbc decoder wrapper. libilbc allows libavcodec to decode the Internet Low Bitrate Codec (iLBC) audio codec. Requires the presence of the libilbc headers and library during configuration. You need to explicitly configure the build with @code{--enable-libilbc}. @subsection Options The following option is supported by the libilbc wrapper. @table @option @item enhance Enable the enhancement of the decoded audio when set to 1. The default value is 0 (disabled). @end table @section libopencore-amrnb libopencore-amrnb decoder wrapper. libopencore-amrnb allows libavcodec to decode the Adaptive Multi-Rate Narrowband audio codec. Using it requires the presence of the libopencore-amrnb headers and library during configuration. You need to explicitly configure the build with @code{--enable-libopencore-amrnb}. An FFmpeg native decoder for AMR-NB exists, so users can decode AMR-NB without this library. @section libopencore-amrwb libopencore-amrwb decoder wrapper. libopencore-amrwb allows libavcodec to decode the Adaptive Multi-Rate Wideband audio codec. Using it requires the presence of the libopencore-amrwb headers and library during configuration. You need to explicitly configure the build with @code{--enable-libopencore-amrwb}. An FFmpeg native decoder for AMR-WB exists, so users can decode AMR-WB without this library. @section libopus libopus decoder wrapper. libopus allows libavcodec to decode the Opus Interactive Audio Codec. Requires the presence of the libopus headers and library during configuration. You need to explicitly configure the build with @code{--enable-libopus}. An FFmpeg native decoder for Opus exists, so users can decode Opus without this library. @c man end AUDIO DECODERS @chapter Subtitles Decoders @c man begin SUBTILES DECODERS @section libaribb24 ARIB STD-B24 caption decoder. Implements profiles A and C of the ARIB STD-B24 standard. @subsection libaribb24 Decoder Options @table @option @item -aribb24-base-path @var{path} Sets the base path for the libaribb24 library. This is utilized for reading of configuration files (for custom unicode conversions), and for dumping of non-text symbols as images under that location. Unset by default. @item -aribb24-skip-ruby-text @var{boolean} Tells the decoder wrapper to skip text blocks that contain half-height ruby text. Enabled by default. @end table @section libaribcaption Yet another ARIB STD-B24 caption decoder using external @dfn{libaribcaption} library. Implements profiles A and C of the Japanse ARIB STD-B24 standard, Brazilian ABNT NBR 15606-1, and Philippines version of ISDB-T. Requires the presence of the libaribcaption headers and library (@url{https://github.com/xqq/libaribcaption}) during configuration. You need to explicitly configure the build with @code{--enable-libaribcaption}. If both @dfn{libaribb24} and @dfn{libaribcaption} are enabled, @dfn{libaribcaption} decoder precedes. @subsection libaribcaption Decoder Options @table @option @item -sub_type @var{subtitle_type} Specifies the format of the decoded subtitles. @table @samp @item bitmap Graphical image. @item ass ASS formatted text. @item text Simple text based output without formatting. @end table The default is @dfn{ass} as same as @dfn{libaribb24} decoder. Some present players (e.g., @dfn{mpv}) expect ASS format for ARIB caption. @item -caption_encoding @var{encoding_scheme} Specifies the encoding scheme of input subtitle text. @table @samp @item auto Automatically detect text encoding. @item jis 8bit-char JIS encoding defined in ARIB STD B24. This encoding used in Japan for ISDB captions. @item utf8 UTF-8 encoding defined in ARIB STD B24. This encoding is used in Philippines for ISDB-T captions. @item latin Latin character encoding defined in ABNT NBR 15606-1. This encoding is used in South America for SBTVD / ISDB-Tb captions. @end table The default is @dfn{ass} as same as @dfn{libaribb24} decoder. Some present players (e.g., @dfn{mpv}) expect ASS format for ARIB caption. @item -font @var{font_name[,font_name2,...]} Specify comma-separated list of font family names to be used for @dfn{bitmap} or @dfn{ass} type subtitle rendering. Only first font name is used for @dfn{ass} type subtitle. If not specified, use internaly defined default font family. @item -ass_single_rect @var{boolean} ARIB STD-B24 specifies that some captions may be displayed at different positions at a time (multi-rectangle subtitle). Since some players (e.g., old @dfn{mpv}) can't handle multiple ASS rectangles in a single AVSubtitle, or multiple ASS rectangles of indeterminate duration with the same start timestamp, this option can change the behavior so that all the texts are displayed in a single ASS rectangle. The default is @var{false}. If your player cannot handle AVSubtitles with multiple ASS rectangles properly, set this option to @var{true} or define @env{ASS_SINGLE_RECT=1} to change default behavior at compilation. @item -replace_fullwidth_ascii @var{boolean} Specify whether to replace MSZ (Middle Size, half width) fullwidth alphanumerics with halfwidth alphanumerics. The default is @var{true}. @item -force_outline_text @var{boolean} Specify whether always render outline text for all characters regardless of the indication by charactor style. The default is @var{false}. @item -outline_width @var{number} (0.0 - 3.0) Specify width for outline text, in dots (relative). The default is @var{1.5}. @item -ignore_background @var{boolean} Specify whether to ignore background color rendering. The default is @var{false}. @item -ignore_ruby @var{boolean} Specify whether to ignore rendering for ruby-like (furigana) characters. The default is @var{false}. @item -replace_drcs @var{boolean} Specify whether to render replaced DRCS characters as Unicode characters. The default is @var{true}. @item -replace_msz_japanese @var{boolean} Specify whether to replace some MSZ (Middle Size; half width) fullwidth japanese special characters with halfwidth ones. The default is @var{true}. @item -replace_msz_glyph @var{boolean} Specify whether to replace MSZ (Middle Size; half width) characters with halfwidth glyphs if the fonts supports it. This option works under FreeType or DirectWrite renderer with Adobe-Japan1 compliant fonts. e.g., IBM Plex Sans JP, Morisawa BIZ UDGothic, Morisawa BIZ UDMincho, Yu Gothic, Yu Mincho, and Meiryo. The default is @var{true}. @item -canvas_size @var{image_size} Specify the resolution of the canvas to render subtitles to; usually, this should be frame size of input video. This only applies when @code{-subtitle_type} is set to @var{bitmap}. The libaribcaption decoder assumes input frame size for bitmap rendering as below: @enumerate @item PROFILE_A : 1440 x 1080 with SAR (PAR) 4:3 @item PROFILE_C : 320 x 180 with SAR (PAR) 1:1 @end enumerate If actual frame size of input video does not match above assumption, the rendered captions may be distorted. To make the captions undistorted, add @code{-canvas_size} option to specify actual input video size. Note that the @code{-canvas_size} option is not required for video with different size but same aspect ratio. In such cases, the caption will be stretched or shrunk to actual video size if @code{-canvas_size} option is not specified. If @code{-canvas_size} option is specified with different size, the caption will be stretched or shrunk as specified size with calculated SAR. @end table @subsection libaribcaption decoder usage examples Display MPEG-TS file with ARIB subtitle by @code{ffplay} tool: @example ffplay -sub_type bitmap MPEG.TS @end example Display MPEG-TS file with input frame size 1920x1080 by @code{ffplay} tool: @example ffplay -sub_type bitmap -canvas_size 1920x1080 MPEG.TS @end example Embed ARIB subtitle in transcoded video: @example ffmpeg -sub_type bitmap -i src.m2t -filter_complex "[0:v][0:s]overlay" -vcodec h264 dest.mp4 @end example @section dvbsub @subsection Options @table @option @item compute_clut @table @option @item -2 Compute clut once if no matching CLUT is in the stream. @item -1 Compute clut if no matching CLUT is in the stream. @item 0 Never compute CLUT @item 1 Always compute CLUT and override the one provided in the stream. @end table @item dvb_substream Selects the dvb substream, or all substreams if -1 which is default. @end table @section dvdsub This codec decodes the bitmap subtitles used in DVDs; the same subtitles can also be found in VobSub file pairs and in some Matroska files. @subsection Options @table @option @item palette Specify the global palette used by the bitmaps. When stored in VobSub, the palette is normally specified in the index file; in Matroska, the palette is stored in the codec extra-data in the same format as in VobSub. In DVDs, the palette is stored in the IFO file, and therefore not available when reading from dumped VOB files. The format for this option is a string containing 16 24-bits hexadecimal numbers (without 0x prefix) separated by commas, for example @code{0d00ee, ee450d, 101010, eaeaea, 0ce60b, ec14ed, ebff0b, 0d617a, 7b7b7b, d1d1d1, 7b2a0e, 0d950c, 0f007b, cf0dec, cfa80c, 7c127b}. @item ifo_palette Specify the IFO file from which the global palette is obtained. (experimental) @item forced_subs_only Only decode subtitle entries marked as forced. Some titles have forced and non-forced subtitles in the same track. Setting this flag to @code{1} will only keep the forced subtitles. Default value is @code{0}. @end table @section libzvbi-teletext Libzvbi allows libavcodec to decode DVB teletext pages and DVB teletext subtitles. Requires the presence of the libzvbi headers and library during configuration. You need to explicitly configure the build with @code{--enable-libzvbi}. @subsection Options @table @option @item txt_page List of teletext page numbers to decode. Pages that do not match the specified list are dropped. You may use the special @code{*} string to match all pages, or @code{subtitle} to match all subtitle pages. Default value is *. @item txt_default_region Set default character set used for decoding, a value between 0 and 87 (see ETS 300 706, Section 15, Table 32). Default value is -1, which does not override the libzvbi default. This option is needed for some legacy level 1.0 transmissions which cannot signal the proper charset. @item txt_chop_top Discards the top teletext line. Default value is 1. @item txt_format Specifies the format of the decoded subtitles. @table @option @item bitmap The default format, you should use this for teletext pages, because certain graphics and colors cannot be expressed in simple text or even ASS. @item text Simple text based output without formatting. @item ass Formatted ASS output, subtitle pages and teletext pages are returned in different styles, subtitle pages are stripped down to text, but an effort is made to keep the text alignment and the formatting. @end table @item txt_left X offset of generated bitmaps, default is 0. @item txt_top Y offset of generated bitmaps, default is 0. @item txt_chop_spaces Chops leading and trailing spaces and removes empty lines from the generated text. This option is useful for teletext based subtitles where empty spaces may be present at the start or at the end of the lines or empty lines may be present between the subtitle lines because of double-sized teletext characters. Default value is 1. @item txt_duration Sets the display duration of the decoded teletext pages or subtitles in milliseconds. Default value is -1 which means infinity or until the next subtitle event comes. @item txt_transparent Force transparent background of the generated teletext bitmaps. Default value is 0 which means an opaque background. @item txt_opacity Sets the opacity (0-255) of the teletext background. If @option{txt_transparent} is not set, it only affects characters between a start box and an end box, typically subtitles. Default value is 0 if @option{txt_transparent} is set, 255 otherwise. @end table @c man end SUBTILES DECODERS