High CPU usage while transcoding from webcam regdardless fps

[BizonGod]

Hello!
I wanted to make a simple video recorder uring 2 or 3 webcams (UVC, 640x480) and PC (old, Athlon 64 3200+).
I need low fps - 5 to 10 per camera. Using one camera CPU usage is as 75%. But I found that CPU usage is high,
no matter how much fps I use, 1, 3, 5 or 10 fps. Everywhere is written the lower fps the lower CPU usage.
Is my situation normal? I use this command to record stream:

vlc v4l2:///dev/video0:fps=1 --sout'#transcode{vcodec=h264,fps=1,vb=256}:std{access=file,mux=mp4,dst=111.mp4}

Thanks,
Karol

[Rémi Denis-Courmont]

The V4L2 input does not yet support custom frame rates, and it never did. That's why.

[mundu]

Try mpgv instead of h264 it might decrease CPU usage a bit.