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Andreas Rheinhardt 4e1fee405f avcodec: Fix invalid uses of ff_codec_open2_recursive() 
Normally no two codecs with FF_CODEC_CAP_INIT_THREADSAFE unset
can be initialized at the same time: a mutex in avcodec_open2()
ensures this. This implies that one cannot simply open a codec
with a non-threadsafe init-function from the init function of
a codec whose own init function is not threadsafe either as the child
codec couldn't acquire the lock.

ff_codec_open2_recursive() exists to get around this limitation:
If the init function of the child codec to be initialized is not
thread-safe, the mutex is unlocked, the child is initialized and
the mutex is locked again. This of course has as a prerequisite that
the parent AVCodecContext actually holds the lock, i.e. that the
parent codec's init function is not thread-safe. If it is, then one
can (and has to) just use avcodec_open2() directly (if the child's
init function is not thread-safe, then avcodec_open2() will have to
acquire the mutex itself (and potentially wait for it), so that it is
perfectly fine for an otherwise thread-safe init function to open
a codec with a potentially non-thread-safe init function via
avcodec_open2()).

Yet several of the users of ff_codec_open2_recursive() have the
FF_CODEC_CAP_INIT_THREADSAFE flag set; this only worked because
all the child codecs' init functions were thread-safe themselves
so that ff_codec_open2_recursive() didn't touch the mutex at all.
But of course the real solution to this is to directly use
avcodec_open2().

Reviewed-by: Anton Khirnov <anton@khirnov.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
2020-12-04 15:46:46 +01:00
compat
doc avfilter/af_stereotools: add support for commands 2020-12-04 15:40:42 +01:00
ffbuild
fftools fftools/cmdutils: also print warnings when using -sinks and -sources 2020-12-03 18:32:57 +01:00
libavcodec avcodec: Fix invalid uses of ff_codec_open2_recursive() 2020-12-04 15:46:46 +01:00
libavdevice avdevice/decklink: warn about too old decklink API version 2020-12-03 18:32:57 +01:00
libavfilter avfilter/af_stereotools: add support for commands 2020-12-04 15:40:42 +01:00
libavformat
libavresample
libavutil avutil/timecode: add av_timecode_init_from_components 2020-12-03 18:32:54 +01:00
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README.md

FFmpeg README

FFmpeg is a collection of libraries and tools to process multimedia content such as audio, video, subtitles and related metadata.

Libraries

  • libavcodec provides implementation of a wider range of codecs.
  • libavformat implements streaming protocols, container formats and basic I/O access.
  • libavutil includes hashers, decompressors and miscellaneous utility functions.
  • libavfilter provides a mean to alter decoded Audio and Video through chain of filters.
  • libavdevice provides an abstraction to access capture and playback devices.
  • libswresample implements audio mixing and resampling routines.
  • libswscale implements color conversion and scaling routines.

Tools

  • ffmpeg is a command line toolbox to manipulate, convert and stream multimedia content.
  • ffplay is a minimalistic multimedia player.
  • ffprobe is a simple analysis tool to inspect multimedia content.
  • Additional small tools such as aviocat, ismindex and qt-faststart.

Documentation

The offline documentation is available in the doc/ directory.

The online documentation is available in the main website and in the wiki.

Examples

Coding examples are available in the doc/examples directory.

License

FFmpeg codebase is mainly LGPL-licensed with optional components licensed under GPL. Please refer to the LICENSE file for detailed information.

Contributing

Patches should be submitted to the ffmpeg-devel mailing list using git format-patch or git send-email. Github pull requests should be avoided because they are not part of our review process and will be ignored.