Quoting Zhao Zhili (2023-12-13 11:37:52) > > > > On Dec 13, 2023, at 18:06, Anton Khirnov <an...@khirnov.net> wrote: > > > > Quoting Zhao Zhili (2023-12-13 10:31:38) > >> > >>> 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. > > > > The submitter claims that piping to ffplay suffers from latency, which > > should not be there and so is either a bug or an improper setup. > > The latency issue may be real or not, I’m concerned with performance. > Colorspace is easy to > be handled in the same process than pipe to ffplay, although it’s missing in > current implementation.
I would think piping yuv4mpeg to ffplay should have very little overhead compared to actual encoding. IMO ffmpeg is just not a GUI program and trying to use it as one will just unavoidably lead to tears. It's not an email client either btw. -- 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".
