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6c7a344b65made the VLCs shared between threads and did so in a way that was designed to support stream reconfigurations, so that the structure containing the VLCs was synced in update_thread_context. The idea was that the currently active VLCs would just be passed along between threads. Yet this was broken by5acbdd2264: Before this commit, submit_packet() was a no-op during flushing for VP3, as it is a no-delay decoder, so it won't produce any output during flushing. This meant that prev_thread in pthread_frame.c contained the last dst thread that update_thread_context() was called for (so that these VLCs could be passed along between threads). Yet after said commit, submit_packet was no longer a no-op during flushing and changed prev_thread in such a way that it did not need to contain any VLCs at all*. When flushing, prev_thread is used to pass the current state to the first worker thread which is the one that is used to restart decoding. It could therefore happen that the decoding thread did not contain the VLCs at all any more after decoding restarts after flushing leading to a crash (this scenario was never anticipated and must not happen at all). There is a simple, easily backportable fix given that we do not support stream reconfigurations (yet) when using frame threading: Don't sync the VLCs in update_thread_context(), instead do it once during init. This fixes forgejo issue #20346 and trac issue #11592. (I don't know why5acbdd2264changed submit_packet() to no longer be a no-op when draining no-delay decoders.) *: The exact condition for the crash is nb_threads > 2*nb_frames. Reviewed-by: Peter Ross <pross@xvid.org> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com> (cherry picked from commit90551b7d80)
FFmpeg README
FFmpeg is a collection of libraries and tools to process multimedia content such as audio, video, subtitles and related metadata.
Libraries
libavcodecprovides implementation of a wider range of codecs.libavformatimplements streaming protocols, container formats and basic I/O access.libavutilincludes hashers, decompressors and miscellaneous utility functions.libavfilterprovides means to alter decoded audio and video through a directed graph of connected filters.libavdeviceprovides an abstraction to access capture and playback devices.libswresampleimplements audio mixing and resampling routines.libswscaleimplements 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,ismindexandqt-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.