Generate a video with a duration of 5.3 seconds, with size 176x144 and a frame rate of 10 frames per second:

testsrc=duration=5.3:size=qcif:rate=10

The following graph description will generate a red source with an opacity of 0.2, with size "qcif" and a frame rate of 10 frames per second:

color=c=red@0.2:s=qcif:r=10

If the input content is to be ignored, nullsrc can be used. The following command generates noise in the luminance plane by employing the geq filter:

nullsrc=s=256x256, geq=random(1)*255:128:128