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MPEG-2 allows to pair an intra field (as first field) together with a P-field. In this case a conformant bitstream has to satisfy certain restrictions in order to ensure that only the I field is used for prediction. See section 7.6.3.5 of the MPEG-2 specifications. We do not check these restrictions; normally we simply allocate dummy frames for reference in order to avoid checks lateron. This happens in ff_mpv_frame_start() and therefore does not happen for a second field. This is inconsistent. Fix this by allocating these dummy frames for the second field, too. This already fixes two bugs: 1. Undefined pointer arithmetic in prefetch_motion() in mpegvideo_motion.c where it is simply presumed that the reference frame exists. 2. Several MPEG-2 hardware accelerations rely on last_picture being allocated for P pictures and next picture for B pictures; e.g. VDPAU returns VDP_STATUS_INVALID_HANDLE when decoding an I-P fields pair because the forward_reference was set incorrectly. 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.