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There are two types of checks for whether the current codec is MPEG-1/2 in mpv_reconstruct_mb_internal(): Those that are required for correctness and those that are not; an example of the latter is "is_mpeg12 || (s->codec_id != AV_CODEC_ID_WMV2)". The reason for the existence of such checks is that mpv_reconstruct_mb_internal() has the av_always_inline attribute and is_mpeg12 is usually inlined, so that in case we are dealing with MPEG-1/2 the above check can be completely optimized away. But is_mpeg12 is not always inlined: it is not in case CONFIG_SMALL is true in which case is_mpeg12 is always zero, so that the checks required for correctness need to check out_format explicitly. This is currently done via a macro in mpv_reconstruct_mb_internal(), so that the fact that it is CONFIG_SMALL that determines this is encoded at two places. This commit changes this by making is_mpeg12 a three-state: DEFINITELY_MPEG12, MAY_BE_MPEG12 and NOT_MPEG12. In the second case, one has to resort to check out_format, in the other cases is_mpeg12 can be taken at face-value. This will allow to make inlining is_mpeg12 more flexible in a future commit. 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.