76b33704b6
For 422 frames we should not use hard coded 8 to calculate mb size for uv plane. Chroma shift should be taken into consideration to be compatiple with different sampling format. The error is reported by fate test when av_cpu_max_align() return 64 on the platform supporting AVX512. This is a hidden error and it is exposed after commit 17a59a634c39b00a680c6ebbaea58db95594d13d. mpeg2enc has a mechanism to reuse frames. When it computes SSE (sum of squared error) on current mb, reconstructed mb will be wrote to the previous mb space, so that the memory can be saved. However if the align is 64, the frame is shared in somewhere else, so the frame cannot be reused and a new frame to store reconstrued data is created. Because the height of mb is wrong when compute sse on 422 frame, starting from the second line of macro block, changed data is read when frame is reused (we need to read row 16 rather than row 8 if frame is 422), and unchanged data is read when frame is not reused (a new frame is created so the original frame will not be changed). That is why commit 17a59a634c39b00a680c6ebbaea58db95594d13d exposes this issue, because it add av_cpu_max_align() and this function return 64 on platform supporting AVX512 which lead to creating a frame in mpeg2enc, and this lead to the different outputs. Signed-off-by: Wenbin Chen <wenbin.chen@intel.com> Signed-off-by: Marton Balint <cus@passwd.hu>
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.