a30c95ed8a
linesize and uvlinesize are supposed to be the common linesize of all the Y/UV-planes of all the currently cached pictures. ff_mpeg_update_thread_context() syncs the pictures, yet it did not sync linesize and uvlinesize. This mostly works, because ff_alloc_picture() only accepts new pictures if they coincide with the linesize of the already provided pictures (if any). Yet there is a catch: Linesize changes are accepted when the dimensions change (in which case the cached frames are discarded). So imagine a scenario where all frame threads use the same dimension A until a frame with a different dimension B is encountered in the bitstream, only to be instantly reverted to A in the next picture. If the user changes the linesize of the frames upon the change to dimension B and keeps the linesize thereafter (possible if B > A), ff_alloc_picture() will report an error when frame-threading is in use: The thread decoding B will perform a frame size change and so will the next thread in ff_mpeg_update_thread_context() as well as when decoding its picture. But the next thread will (presuming it is not the same thread that decoded B, i.e. presuming >= 3 threads) not perform a frame size change, because the new frame size coincides with its old frame size, yet the linesize it expects from ff_alloc_picture() is outdated, so that it errors out. It is also possible for the user to use the original linesizes for the frame after the frame that reverted back to A; this will be accepted, yet the assumption that of all pictures are the same will be broken, leading to segfaults. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
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.