wiki:

Using libav*


Version 7 (modified by rogerdpack, 4 years ago) (diff)

add doxygen links, clarify some libs

FFmpeg itself is composed of several subcomponents that can be used individually, and outside of FFmpeg, for instance in your own program. These are

  • libavformat which contains muxer and de-muxer information and capabilities.
  • libavcodec which contains all the (built-in) video encoding and decoding codecs that FFmpeg contains.
  • libswscale contains the (raw pixel) format conversions, and also high speed/assembly optimized versions of certain scaling routines.
  • libavfilter contains the filters FFmpeg contains, like adjusting audio sample rate, etc.
  • libavdevice contains interfaces for working with "local devices" for instance webcams in windows, line-in audio in linux, etc.
  • libpostproc ??
  • libswresample audio conversion routines (?)
  • libavresample audio conversion routines (?)
  • libavutil "contains the code shared across all the other FFmpeg libraries" so isn't used by itself, that I know of.

Getting started

There is not much "web based" official documentation for using these libraries.

Check doc/examples, also doxygen documentation is fairly complete and should work as reference (example: the example codes as doxygen).

In general, you must have the appropriate library compiled/available on your machine (for instance, if using packages, something like libswscale-dev must be installed, or configure, build, and install FFmpeg yourself using the --enable-shared configure option), then you include the appropriate header file in your C code, then link against that library's linker file, like "gcc input.c -lswscale" or the like during the linker phase.

Tutorials

The web has a few tutorials, some of which are out of date. The doc/examples files usually use the latest ABI, however, should be more trustworthy.

Using libavformat and libavcodec by Martin Böhme, a good overview of the FFmpeg APIs, though quite out dated.

An FFmpeg and SDL Tutorial by Stephen Dranger, explains how to write a video player based on FFmpeg (updated source code for that tutorial, by Michael Penkov, is also now available).

Hints

libavformat

Its Doxygen docu. see most of the tutorials, as well.

libavcodec

Its Doxygen docu. see most of the tutorials, as well.

Determining the right values to pass to AVCodecContext:

One user shared this advice for determining all the correct values:

[An] approach to figuring this out is:

  1. come up with the ffmpeg app command line which does what you want
  1. use the gdb debugger to execute the ffmpeg_g app, put a breakpoint on avcodec_encode_audio2() (or whichever method you need), and see what values the ffmpeg app uses for AVPacket and for the (audio or otherwise) related fields in AVCodecContext.

libswresample

This file is also given as documentation. You may find some docu under the doxygen of libavcodec "Audio resampling".

libswscale

This file is also given as documentation.

libavdevice

Its doxygen documentation.

Contact

If you have problems, one place to get help is to ask the libav-user mailing list, its description: "This list is about using libavcodec, libavformat, libavutil, libavdevice and libavfilter." IRC might work also.