On Fri, 15 Aug 2025 15:41:07 +0200, Jan Stary <h...@stare.cz> wrote: > > On Aug 15 15:30:29, kir...@korins.ky wrote: > > > a framerate confusion for mjpeg, which I suspect is a ffmpeg problem > > > not related to this: sometimes it will play back the video using > > > a framerate different from recording (such as 25 vs 20). > > > > > Interesting, I had reported to ffmpeg upstream an issue with my Elgato > > webcam: when I stream with 4K 60fps, I have "frozen" picture. > > > > Quite possible that root cause is mjpeg and that ffmpeg uses CPU to decode > > it, if your CPU isn't very fast, it may be an issue. > > May aim was to not do any decoding: get the mjpeg frames > as they come from the camera and just store them, > hence the -vcodec copy in > > ffmpeg -y -vcodec mjpeg -i /dev/video -vcodec copy /tmp/video.mjpeg >
Same, I had frozen stream when run: ffmpeg -input_format mjpeg -video_size 3840x2160 -framerate 60 -i /dev/video1 -codec copy -t 10 framerate-60.mp4 and I had reply from ffmpeg upstream: That pretty much means your CPU is too weak to decode mjpeg of that quality in real time. Try one of the various hardware decoders that support mjpeg. and from this I made a conclusion that it reencodes frame, and not just copies. But I haven't dig into this depper. -- wbr, Kirill
