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b5d146d17c
call_kernel() obtains the command buffer and compute encoder from
property getters (mtlQueue.commandBuffer, buffer.computeCommandEncoder),
which return autoreleased references under the non-ARC build, and then
releases them via ff_objc_release(). That is an over-release: when the
enclosing autorelease pool is drained, the objects are released a second
time and the process crashes with EXC_BAD_ACCESS in objc_release.
On current macOS this is reproducible with the ffmpeg CLI itself. The
filter thread's thread-local autorelease pool is popped during pthread
TSD cleanup at thread exit, so any run that used yadif_videotoolbox
crashes when the filter thread terminates:
ffmpeg -init_hw_device videotoolbox=vt -filter_hw_device vt \
-f lavfi -i testsrc2=size=640x480:rate=30 \
-vf setfield=tff,format=nv12,hwupload,yadif_videotoolbox,\
hwdownload,format=nv12 -frames:v 20 -f null -
Thread 11 Crashed:: vf#0:0
0 libobjc.A.dylib objc_release + 16
1 libobjc.A.dylib AutoreleasePoolPage::releaseUntil(objc_object**) + 204
2 libobjc.A.dylib objc_autoreleasePoolPop + 244
3 libobjc.A.dylib objc_tls_direct_base<...>::dtor_(void*) + 156
4 libsystem_pthread.dylib _pthread_tsd_cleanup + 620
5 libsystem_pthread.dylib _pthread_exit + 84
Host applications hit the same crash earlier, for example when a
dispatch queue drains its last-resort pool after a work item that ran
the filter.
Wrap the kernel invocation in @autoreleasepool and drop the manual
releases, making the pool pop the single balanced release and draining
the Metal transients once per frame. The ff_objc_release() calls on the
s->mtl* members in do_uninit() stay: those hold owned references
obtained from new* methods.
(cherry picked from commit 7f2e5cdd7c)
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.