Add the null video filter.
[libav.git] / doc / vfilters.texi
CommitLineData
1f09ab5e
SS
1\input texinfo @c -*- texinfo -*-
2
3@settitle Video Filter Documentation
4@titlepage
5@sp 7
6@center @titlefont{Video Filter Documentation}
7@sp 3
8@end titlepage
9
10
11@chapter Introduction
12
13Libavfilter is the filtering API of FFmpeg. It is the substitute of the
14now deprecated 'vhooks' and started as a Google Summer of Code project.
15
16Integrating libavfilter into the main FFmpeg repository is a work in
17progress. If you wish to try the unfinished development code of
18libavfilter then check it out from the libavfilter repository into
19some directory of your choice by:
20
21@example
22 svn checkout svn://svn.ffmpeg.org/soc/libavfilter
23@end example
24
25And then read the README file in the top directory to learn how to
26integrate it into ffmpeg and ffplay.
27
28But note that there may still be serious bugs in the code and its API
29and ABI should not be considered stable yet!
30
31In libavfilter, it is possible for filters to have multiple inputs and
32multiple outputs.
33To illustrate the sorts of things that are possible, we can
34use a complex filter graph. For example, the following one:
35
36@example
37input --> split --> fifo -----------------------> overlay --> output
38 | ^
39 | |
40 +------> fifo --> crop --> vflip --------+
41@end example
42
43splits the stream in two streams, sends one stream through the crop filter
44and the vflip filter before merging it back with the other stream by
45overlaying it on top. You can use the following command to achieve this:
46
47@example
48./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]
49@end example
50
51where input_video.avi has a vertical resolution of 480 pixels. The
52result will be that in output the top half of the video is mirrored
53onto the bottom half.
54
55Video filters are loaded using the @var{-vfilters} option passed to
56ffmpeg or to ffplay. Filters in the same linear chain are separated by
57commas. In our example, @var{split, fifo, overlay} are in one linear
58chain, and @var{fifo, crop, vflip} are in another. The points where
59the linear chains join are labeled by names enclosed in square
60brackets. In our example, that is @var{[T1]} and @var{[T2]}. The magic
61labels @var{[in]} and @var{[out]} are the points where video is input
62and output.
63
64Some filters take in input a list of parameters: they are specified
65after the filter name and an equal sign, and are separated each other
66by a semicolon.
67
68There exist so-called @var{source filters} that do not have a video
69input, and we expect in the future some @var{sink filters} that will
70not have video output.
71
72@chapter Available video filters
73
74When you configure your FFmpeg build, you can disable any of the
75existing video filters.
76The configure output will show the video filters included in your
77build.
78
79Below is a description of the currently available video filters.
80
7b018b1d
SS
81@section null
82
83Pass the source unchanged to the output.
84
1f09ab5e 85@bye