> On Dec 13, 2023, at 17:08, Anton Khirnov <an...@khirnov.net> wrote: > > Quoting Zhao Zhili (2023-12-12 18:27:39) >> Now it's time to talk about the libavdevice/sdl issue. >> >> SDL output is broken with ffmpeg multithread refactor. SDL 'muxer' >> write_header >> and write_packet must be run in the same thread. And to make it work portable >> and reliable, SDL 'muxer' must be run in main thread. It's a common >> requirement >> for render to be run in main thread. >> >> There are at least two trac tickets for the same issue: #10644 and #10649. >> >> And there are two patches for the issue: >> https://patchwork.ffmpeg.org/project/ffmpeg/patch/20230918063728.198377-1-haihao.xi...@intel.com/ >> https://patchwork.ffmpeg.org/project/ffmpeg/patch/20231101090115.10655-1-angus.c...@intel.com/ >> >> There patches might work on Linux, but not portable. >> >> A simple workaround is pipe the output of ffmpeg to ffplay: >> >> ./ffmpeg -re -i /e/video/cctv.mp4 -an -f yuv4mpegpipe - |ffplay - >> >> To fix it, another thread can be used to drive transcode rather than main >> thread. >> A main loop should be created on main thread, and prepared to handle any >> special >> tasks like render. It sounds a lot of work. I'm not sure if it worth for a >> single use case. >> However, maybe we can have a libavfilter/vsink_preview after that. >> >> What should we do? > > Honestly I don't see how this could be done in ffmpeg CLI without > disgusting hacks, but before that the question is: why is there an SDL > "muxer" and why would anyone want to use it in ffmpeg CLI? What actual > use cases does it serve that cannot be better handled otherwise?
I pasted wrong tickets, they are #10625 and #10649. https://trac.ffmpeg.org/ticket/10625 The use case is realtime preview. The function lavd/sdl2 provides is limited. A vsink_preview filter is more appropriate. It has the same thread issue with libavfilter. > > -- > Anton Khirnov > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel > > To unsubscribe, visit link above, or email > ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe". _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
