Can't change settings using v4l2ucp (Linux)



I own two AV.IO HD devices

One of them doesn’t respond to changing brightness and contrast using v4l2ucp in Linux.
v4l2ucp can see the device, change and reset the values but it has no effect on the grabber.
Other than that the grabber works fine.

The other device behaves as expected.
Both have the same (latest) firmware.



Are the sources both VGA into the two HD devices? The brightness / contrast adjustments are only for VGA analog input signals, but wouldn’t apply to DVI or HDMI input signals as these are digital.