On Wed, Dec 06, 2017 at 15:58:28 +0000, Dhananjay Umap wrote: > ffmpeg -f video4linux2 -i /dev/video0 -start_number 1 -vframes 250 -c:v mpeg4 > -qscale:v 1 test1.avi > As I can see below the rawvideo is at 1920x1080 format, but the input to the > card is 4K as well as the card is 4K capable.
> If I use the following command, I capture 4K video with 25 fps. > ./ffmpeg -f video4linux2 -i /dev/video0 -s 3840x2160 -start_number 1 -vframes > 250 -c:v mpeg4 -qscale:v 1 test.avi > In this case scaling is performed by the ffmpeg to 4K which affects > the KPI of the captured video. This also affect the speed of the > capture since ffmpeg is processing the video to 4K during capture > which eventually affects the KPI for the captured video. You need to tell the v4l2 device to choose the correct input resolution. The input option "-video_size <resolution>" should work. (You may also want to choose the correct "-pixel_format".) Yet even then, ffmpeg will convert 3840x2160 (raw) to 3840x2160 (mpeg4), and take about as much CPU as when it does soft upscaling 1920x1080 -> 3840x2160). Only that the quality will be better. You need to find encoding settings which are faster (at the cost of quality or size/compression ratio). With x264, I would try various presets, such as "-preset fast". I'm not sure what to do for the mpeg4 codec, Google or others on this list should help you. The default of 200 kb/s is probably the issue, I'm guessing that the codec many be trying really hard to compress the hell out of your HD images (and won't succeed). Cheers, Gruß nach Nürnberg, Moritz _______________________________________________ ffmpeg-user mailing list [email protected] http://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email [email protected] with subject "unsubscribe".
