b6eaa3928e
The way videotoolbox hooks in as a hwaccel is pretty hacky. The VT decode API is not invoked until end_frame(), so alloc_frame() returns a dummy frame with a 1-byte buffer. When end_frame() is eventually called, the dummy buffer is replaced with the actual decoded data from VTDecompressionSessionDecodeFrame(). When the VT decoder fails, the frame returned to the h264 decoder from alloc_frame() remains invalid and should not be used. Before 9747219958060d8c4f697df62e7f172c2a77e6c7, it was accidentally being returned all the way up to the API user. After that commit, the dummy frame was unref'd so the user received an error. However, since that commit, VT hwaccel failures started causing random segfaults in the h264 decoder. This happened more often on iOS where the VT implementation is more likely to throw errors on bitstream anomolies. A recent report of this issue can be see in http://ffmpeg.org/pipermail/libav-user/2016-November/009831.html The issue here is that the dummy frame is still referenced internally by the h264 decoder, as part of the reflist and cur_pic_ptr. Deallocating the frame causes assertions like this one to trip later on during decoding: Assertion h->cur_pic_ptr->f->buf[0] failed at src/libavcodec/h264_slice.c:1340 With this commit, we leave the dummy 1-byte frame intact, but avoid returning it to the user. This reverts commit 9747219958060d8c4f697df62e7f172c2a77e6c7. Signed-off-by: wm4 <nfxjfg@googlemail.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.
- ffserver is a multimedia streaming server for live broadcasts.
- 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.