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In some situations, MMAL won't return a decoded frame for certain input frames. This can happen if a frame fails to decode, or if a packet does not actually contain a complete frame. In these situations, we would deadlock (or actually timeout) waiting for an expected output frame, which is not ideal. On the other hand, there are situations where we definitely have to block to avoid deadlocks. (This mess is a consequence of trying to map MMAL's asynchronous and flexible dataflow to libavcodec, which is more static and rigid.) Solve this by doing a blocking wait only if the amount of buffered data is too big. The whole purpose of the blocking wait is to avoid excessive buffering of input data, so we can skip it if it appears to be low. The consequence is that libavcodec can gracefully return no frame to the API user. We want to track the number of full packets to make our heuristic work. But MMAL buffers are fixed-size, requiring splitting large packets. This is why the previous commit is needed. We use the ..._FRAME_END flag to remember packet boundaries, but MMAL does not preserve these buffer flags when returning buffers to the user. Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
Libav
Libav 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.libavresampleimplements audio mixing and resampling routines.libswscaleimplements color conversion and scaling routines.
Tools
- avconv is a command line toolbox to manipulate, convert and stream multimedia content.
- avplay is a minimalistic multimedia player.
- avprobe is a simple analisys 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
Conding examples are available in the doc/example directory.
License
Libav codebase is mainly LGPL-licensed with optional components licensed under GPL. Please refer to the LICENSE file for detailed information.