v4l2-ctl missing controls (16MP Autofocus Camera)

[giano574]

When executing v4l2-ctl --list-ctrls -d /dev/v4l-subdev1 only focus_absolute is listed as a control. I need to be able to adjust at least the shutter speed and gain on the fly. Using libcamera-vid --shutter x --gain x works, so why can't I use v4l2-ctl to adjust it?

[kbingham]

When libcamera is in control of the camera, it is responsible for handling the gain and exposure.
What is your use case?

[giano574]

I'm creating a video stream using rtsp-simple-server, which uses libcamera (not apps) directly. I need to be able to adjust shutter speed and gain on the fly, and since v4l2-ctl -d /dev/v4l-subdev1 -c focus_absolute=850 works, I thought I would be able to also adjust the shutter speed and gain in the same way.
Apparently /dev/v4l-subdev0 is the device that exposes everything other than focus_absolute but changing exposure and analogue_gain doesn't work, I assume because - as you said - libcamera is in control.

[kbingham]

I would say this should be an issue on the rtsp-simple-server then. Can you reference it here when you create it so I can follow it please?

[giano574]

bluenviron/mediamtx#1159
Is it documented somewhere in libcamera docs what one would have to do to change camera controls in the least "intrusive" way? From what I could gather from reading the doxygen docs, it seems like one would at least have to call stop() on the libcamera::Camera followed by a call to start() with an updated libcamera::ControlList. Is that the case?

[kbingham]

It doesn't have to stop and restart no - the request which are queued to get the frames can supply a control list as well. The desired controls should be part of that list which is submitted. That request is submitted by the rtsp-simple-server in the use case you've described, so rtsp-simple-server needs to add the controls.