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c13d959343
This change improves the performance and multicore scalability of the vp9 codec for streaming single-pass encoded videos by taking advantage of up to 64 cores in the system. The current thread limit for ffmpeg codecs is 16 (MAX_AUTO_THREADS in pthread_internal.h) due to a limitation in H.264 codec that prevents more than 16 threads being used. Experiments show that increasing the thread limit to 64 for vp9 improves the performance for encoding 4K raw videos for streaming by up to 47% compared to 16 threads, and from 20-30% for 32 threads, with the same quality as measured by the VMAF score. Rationale for this change: Vp9 uses tiling to split the video frame into multiple columns; tiles must be at least 256 pixels wide, so there is a limit to how many tiles can be used. The tiles can be processed in parallel, and more tiles mean more CPU threads can be used. 4K videos can make use of 16 threads, and 8K videos can use 32. Row-mt can double the number of threads so 64 threads can be used. Signed-off-by: James Zern <jzern@google.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.