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When switching to the XviD IDCT, the IDCT permutation can change. Given that we already permute the quant matrices when parsing them, they need to be permuted, too. Up until now this has not been done; instead the header has been parsed again in the expectation that the currently active quant matrix is contained in this header. This expectation is wrong; it is for example wrong when the VOL header is only available via extradata (such a file can be easily created from xvid_vlc_trac7411.h263 (in the FATE suite) via the remove_extra BSF). It could also be wrong if the XviD user data is only available in a subsequent packet. This commit therefore switches to permuting the relevant matrices directly. It also stops parsing the header a second time when switching to the XviD IDCT. (I wonder whether ff_mpv_idct_init() should take alternate_scan into account when initializing permutated_intra_h_scantable as the decoder does. Does the MPEG-4 encoder use a wrong scantable in this case?) 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.