Re: [FFmpeg-user] How to drop frames to limit memory usage (or keep latency low)?
On 4/3/2018 8:55 PM, Adam Nielsen wrote: I've had a look through the manpage but I can't find any options that can do this. The -r and -vsync options seem to only drop frames to match a constant framerate (rather than trying to minimise latency) and -frame_drop_threshold looks to be similar, keeping up with timestamps rather than affecting latency. Do you -need- full-rate motion? It sounds like you need to drop frames to match a constant FR that you then transcode. You might be able to use the framestep filter to discard every other frame, transcode, then use -r to set the desired output rate which will dup frames to fill the time. (I have not tried this myself.) There's a some vaguely apropos answer regarding framestep at https://video.stackexchange.com/questions/16552/4x-resample-videoframes-using-ffmpeg. Later, z! ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
Re: [FFmpeg-user] How to drop frames to limit memory usage (or keep latency low)?
Hi Victor, Many thanks for your reply! > What you could do is reduce the output framerate by using the `-r > (framerate)` or the `fps` video filter, which will reduce the > encoding load on the CPU. This looks like the best option for me. With fps=15, removing the rotation filter, and adding your -tune stillimage suggestion, I can get 15fps transcoding at 1.05x realtime. I imagine this will slow down and start using more memory for buffering if there's a lot of movement in the image, but being slightly faster than realtime means it should catch up again once the movement settles down. > Also, I'm sure `mpeg2video` does not support encoding presets. If you > want fast encoding, you may want to try `libx264` with `-preset > ultrafast`, `-tune stillimage` and `-deblock 0:0`, since that can be > faster than MPEG-2 depending on your CPU architecture, and maybe more > efficient. I tried this however it makes no difference to the encoding speed on the Intel NUC platform I'm using (Intel i3 @ 2.1GHz). I did end up switching to libx264 now that I realise it's no slower, as this matches the format of the other files I'm getting from my other cameras, however there was unfortunately no speed increase just from changing the codec. The stillimage tuning option did provide a noticeable speed boost though. > If available on your platform, you may also want to try > hardware-accelerated H 264 encoding APIs. You can find some info > here: https://trac.ffmpeg.org/wiki/HWAccelIntro (note: you may have > to compile a custom build of FFmpeg to enable this feature, as > pre-built ones aren't usually compiled for it. I have thought about this as the video is coming from a Raspberry Pi, which apparently has hardware H264 encoding now. I am not sure if it has enough power to encode two H264 streams at the same time (both the Pi camera and the MJPEG USB camera that is the root cause of this issue) but if it can, that will probably be the best option. Thanks again for your help! Cheers, Adam. ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
Re: [FFmpeg-user] How to drop frames to limit memory usage (or keep latency low)?
Hi, Adam. I don't see any way to do automatic frame skipping in FFmpeg. What you could do is reduce the output framerate by using the `-r (framerate)` or the `fps` video filter, which will reduce the encoding load on the CPU. Adjust this until the average encoding throughput is 1.00x (that means, when the average number of frames encoded per second is equal to the specified framerate, and your average CPU load is below ~90% just to be safe). Also, I'm sure `mpeg2video` does not support encoding presets. If you want fast encoding, you may want to try `libx264` with `-preset ultrafast`, `-tune stillimage` and `-deblock 0:0`, since that can be faster than MPEG-2 depending on your CPU architecture, and maybe more efficient. If available on your platform, you may also want to try hardware-accelerated H 264 encoding APIs. You can find some info here: https://trac.ffmpeg.org/wiki/HWAccelIntro (note: you may have to compile a custom build of FFmpeg to enable this feature, as pre-built ones aren't usually compiled for it. Victor Carneiro ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
