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