mirror of
https://github.com/FFmpeg/FFmpeg.git
synced 2024-12-18 03:19:31 +02:00
227 lines
6.5 KiB
Plaintext
227 lines
6.5 KiB
Plaintext
\input texinfo @c -*- texinfo -*-
|
|
|
|
@settitle Libavfilter Documentation
|
|
@titlepage
|
|
@sp 7
|
|
@center @titlefont{Libavfilter Documentation}
|
|
@sp 3
|
|
@end titlepage
|
|
|
|
|
|
@chapter Introduction
|
|
|
|
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.
|
|
|
|
Integrating libavfilter into the main FFmpeg repository is a work in
|
|
progress. If you wish to try the unfinished development code of
|
|
libavfilter then check it out from the libavfilter repository into
|
|
some directory of your choice by:
|
|
|
|
@example
|
|
svn checkout svn://svn.ffmpeg.org/soc/libavfilter
|
|
@end example
|
|
|
|
And then read the README file in the top directory to learn how to
|
|
integrate it into ffmpeg and ffplay.
|
|
|
|
But note that there may still be serious bugs in the code and its API
|
|
and ABI should not be considered stable yet!
|
|
|
|
@chapter Tutorial
|
|
|
|
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 in.avi -s 240x320 -vfilters "[in] split [T1], fifo, [T2] overlay= 0:240 [out]; [T1] fifo, crop=0:0:-1:240, vflip [T2]
|
|
@end example
|
|
|
|
where input_video.avi has a vertical resolution of 480 pixels. The
|
|
result will be that in output the top half of the video is mirrored
|
|
onto the bottom half.
|
|
|
|
Video filters are loaded using the @var{-vfilters} option passed to
|
|
ffmpeg or to 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 magic
|
|
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 each other
|
|
by a semicolon.
|
|
|
|
There exist so-called @var{source filters} that do not have a video
|
|
input, and we expect in the future some @var{sink filters} that will
|
|
not have video output.
|
|
|
|
@chapter Available video filters
|
|
|
|
When you configure your FFmpeg build, you can disable any of the
|
|
existing video filters.
|
|
The configure output will show the video filters included in your
|
|
build.
|
|
|
|
Below is a description of the currently available video filters.
|
|
|
|
@section crop
|
|
|
|
Crop the input video to x:y:width:height.
|
|
|
|
@example
|
|
./ffmpeg -i in.avi -vfilters "crop=0:0:0:240" out.avi
|
|
@end example
|
|
|
|
``x'' and ``y'' specify the position of the top-left corner of the
|
|
output (non-cropped) area.
|
|
|
|
The default value of ``x'' and ``y'' is 0.
|
|
|
|
The ``width'' and ``height'' parameters specify the width and height
|
|
of the output (non-cropped) area.
|
|
|
|
A value of 0 is interpreted as the maximum possible size contained in
|
|
the area delimited by the top-left corner at position x:y.
|
|
|
|
For example the parameters:
|
|
|
|
@example
|
|
"crop=100:100:0:0"
|
|
@end example
|
|
|
|
will 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.
|
|
|
|
The default value of ``width'' and ``height'' is 0.
|
|
|
|
@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''.
|
|
|
|
The following command:
|
|
|
|
@example
|
|
./ffmpeg -i in.avi -vfilters "format=yuv420p" out.avi
|
|
@end example
|
|
|
|
will convert the input video to the format ``yuv420p''.
|
|
|
|
@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''.
|
|
|
|
The following command:
|
|
|
|
@example
|
|
./ffmpeg -i in.avi -vfilters "noformat=yuv420p, vflip" out.avi
|
|
@end example
|
|
|
|
will make libavfilter use a format different from ``yuv420p'' for the
|
|
input to the vflip filter.
|
|
|
|
@section null
|
|
|
|
Pass the source unchanged to the output.
|
|
|
|
@section scale
|
|
|
|
Scale the input video to width:height and/or convert the image format.
|
|
|
|
For example the command:
|
|
|
|
@example
|
|
./ffmpeg -i in.avi -vfilters "scale=200:100" out.avi
|
|
@end example
|
|
|
|
will scale the input video to a size of 200x100.
|
|
|
|
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 ``width'' or ``height'' is 0, the respective input
|
|
size is used for the output.
|
|
|
|
If the value for ``width'' or ``height'' is -1, the scale filter will
|
|
use, for the respective output size, a value that maintains the aspect
|
|
ratio of the input image.
|
|
|
|
The default value of ``width'' and ``height'' is 0.
|
|
|
|
@section slicify
|
|
|
|
Pass the images of input video on to next video filter as multiple
|
|
slices.
|
|
|
|
@example
|
|
./ffmpeg -i in.avi -vfilters "slicify=32" out.avi
|
|
@end example
|
|
|
|
The filter accepts the slice height as parameter. If the parameter is
|
|
not specified it will use the default value of 16.
|
|
|
|
Adding this in the beginning of filter chains should make filtering
|
|
faster due to better use of the memory cache.
|
|
|
|
@section vflip
|
|
|
|
Flip the input video vertically.
|
|
|
|
@example
|
|
./ffmpeg -i in.avi -vfilters "vflip" out.avi
|
|
@end example
|
|
|
|
@chapter Available video sources
|
|
|
|
Below is a description of the currently available video sources.
|
|
|
|
@section nullsrc
|
|
|
|
Null video source, never return images. It is mainly useful as a
|
|
template and to be employed in analysis / debugging tools.
|
|
|
|
It accepts as optional parameter a string of the form
|
|
``width:height'', where ``width'' and ``height'' specify the size of
|
|
the configured source.
|
|
|
|
The default values of ``width'' and ``height'' are respectively 352
|
|
and 288 (corresponding to the CIF size format).
|
|
|
|
@chapter Available video sinks
|
|
|
|
Below is a description of the currently available video sinks.
|
|
|
|
@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.
|
|
|
|
@bye
|