4e7e30bbe0
cbs is currently inconsistent regarding the opaque field that can be used as a special argument to av_buffer_create in order to be used during freeing the buffer: ff_cbs_alloc_unit_content and all the free functions used name this parameter as if it should contain a pointer to the unit whose content is about to be created; but both ff_cbs_alloc_unit_content as well as ff_cbs_h264_add_sei_message actually use a pointer to the CodedBitstreamContext as opaque. It should actually be neither, because it is unneeded (as is evidenced by the fact that none of the free functions use this pointer at all) and because it ties the unit's content to the lifetime of other objects, although a refcounted buffer is supposed to have its own lifetime that only ends when its reference count reaches zero. This problem manifests itself in the pointer becoming dangling. The pointer to the unit can become dangling if another unit is added to the fragment later as happens in the bitstream filters; in this case, the pointer can point to the wrong unit (if the fragment's unit array needn't be relocated) or it can point to where the array was earlier. It can also become dangling if the unit's content is meant to survive the resetting of the fragment it was originally read with. This applies to the extradata of H.264 and HEVC. The pointer to the context can become dangling if the context is closed before the content is freed. Although this doesn't seem to happen right now, it could happen, in particular if one uses different CodedBitstreamContexts for in- and output. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.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 a mean to alter decoded Audio and Video through chain of 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.