Raspberry Pi Stack Exchange is a question and answer site for users and developers of hardware and software for Raspberry Pi. It only takes a minute to sign up.
Sign up to join this community
To record video from my USB webcam I use ffmpeg with v4l2 driver (command below).
ffmpeg -f v4l2 -r 30 -s 640x480 -an -sn -i /dev/video0 -f avi temp
Unfortunately fps is too low for 640x480 (around 5 fps). During recording, ffmpeg loads the cpu by 6%. I tried to change the resolution to 1920x1080, but FPS has not changed and cpu load increased to 20%.
How to fix it?
Framerate can be limited by either the CPU performance (how fast the RPi can accept the frames), by the stream format (how fast can a webcam produce given frames), or by ambient conditions (low light requiring long exposition time). Since the CPU load in your first case is low, it looks like the problem is of the second/third kind.
Check out what video stream formats your webcam supports by running
v4l2-ctl --list-formats-ext
and pick a format which has high enough FPS. If you still get low FPS, try pointing your webcam at a light source and see if that increases the FPS. If that helps, you need to provide more light in the scene you're capturing, or buy a webcam which works better in the dark (expensive models often do).
