Webcam is greyed out, even when v4l2loopback device is present.

[Kundan]

The webcam field in the Xpra Client is greyed out, even when we create a v4l2loopback device by modprobe v4l2loopback devices=1 on Ubuntu 16.04.
I checked the device. The virtual device was present.
The command, I used to start xpra and attach it.

xpra start :10 --bind-tcp=192.168.0.20:10000 -d webcam --webcam=/dev/video1 &
xpra attach tcp:192.168.0.20:10000

[Kundan]

It seems the reason for this is that, the v4loloopback devices created on Ubuntu 16.04 (Installed through sudo apt) has exclusive_caps set to 1 by default. It means, it won't expose the VIDEO_CAPTURE capabilities until we write anything to it. But, it seems, here in Xpra we are checking for the device capabilities much earlier, which doesn't report VIDEO_CAPTURE capability since nothing was written to it, at that point of time. This leads to webcam support being disabled or greyed out.

After, creating Video devices through,

sudo modprobe v4l2loopback devices=1 exclusive_caps=0

It works.

[Kundan]

xpra log without any exclusive_caps option while loading v4l2loopback device, The command is sudo modprobe v4l2loopback devices=1, seems to be equivalent to adding option exclusive_caps=1

[Kundan]

The xpra log after starting the server, when the v4loopback device was created by adding exclusive_caps=0.

[Antoine Martin]

Good catch, does r16480 fix things? (disables the check on Debian and Ubuntu only)

[Kundan]

Yes, Antoine,
Now, webcam option is enabled on Ubuntu 16.04 and working properly.

Thanks a lot.