v4l2-ctl not changing from default webcam

Question

I am using v4l2-ctl from command line to change exposure values of usb camera but I cannot change the device from built in webcam When I am using v4l2-ctl d /dev/video1 - it gives no error but it does nothing at all

Answer 1

you might be using the wrong cmd.

• first of all, you need to specify -d to select a different device (mind the --prefix; it is missing in the Q).

  but simply running v4l2-ctl -d /dev/video1 will not do anything with the device (you don't specify what to do)

• so you also need to tell v4l2-ctl to change the exposure-time (or whatever you want to do) with the -c <ctrl>=<val> switch

so your command should look like:

 v4l2-ctrl -d /dev/video1 -c exposure_absolute=3000

but then, your device simply may not support setting the exposure time and simply ignore any requests (it should not announce support for setting the exposure if it cannot change it, but often device drivers are a bit easygoing)