[Bug]: Device lose video capture capability!

[GreatAg]

Is there an existing issue for this?

• I have searched the existing issues

Detail

I am using v4l2loopback for webcam as a virtual device in container for chrome application.
Here is the scenario:
1- i build the source and load the devices with exclusive_caps
2- i run the container and map the device into container using --device flag
3- open the webcam test in chrome and everything is fine
4- delete the container and run again
5- that device no longer known as a webcam or capture device!!

I run v4l2-ctl device=/dev/video2 --all before and after using it in container and find out after destroy the container the device lose it's capture device capability!!

Here is the log before i run container at fresh loading:

root@dmz:/var/modules/v4l2# v4l2-ctl --device=/dev/video2 --all
Driver Info:
	Driver name      : v4l2 loopback
	Card type        : test
	Bus info         : platform:v4l2loopback-002
	Driver version   : 5.4.255
	Capabilities     : 0x85200002
		Video Output
		Read/Write
		Streaming
		Extended Pix Format
		Device Capabilities
	Device Caps      : 0x05200002
		Video Output
		Read/Write
		Streaming
		Extended Pix Format
Priority: 2
Video output: 0 (loopback in)
Format Video Output:
	Width/Height      : 0/0
	Pixel Format      : 'BGR4' (32-bit BGRA/X 8-8-8-8)
	Field             : None
	Bytes per Line    : 0
	Size Image        : 0
	Colorspace        : sRGB
	Transfer Function : Default (maps to sRGB)
	YCbCr/HSV Encoding: Default (maps to ITU-R 601)
	Quantization      : Default (maps to Full Range)
	Flags             : 
Streaming Parameters Video Capture:
	Frames per second: 30.000 (30/1)
	Read buffers     : 2
Streaming Parameters Video Output:
	Frames per second: 30.000 (30/1)
	Write buffers    : 2

User Controls

                    keep_format 0x0098f900 (bool)   : default=0 value=0
              sustain_framerate 0x0098f901 (bool)   : default=0 value=0
                        timeout 0x0098f902 (int)    : min=0 max=100000 step=1 default=0 value=0
               timeout_image_io 0x0098f903 (bool)   : default=0 value=0

And this is after i remove the container:

root@dmz:/dev# v4l2-ctl --device=/dev/video2 --all
Driver Info:
	Driver name      : v4l2 loopback
	Card type        : test
	Bus info         : platform:v4l2loopback-002
	Driver version   : 5.4.255
	Capabilities     : 0x85200000
		Read/Write
		Streaming
		Extended Pix Format
		Device Capabilities
	Device Caps      : 0x05200000
		Read/Write
		Streaming
		Extended Pix Format
Priority: 2

User Controls

                    keep_format 0x0098f900 (bool)   : default=0 value=0
              sustain_framerate 0x0098f901 (bool)   : default=0 value=0
                        timeout 0x0098f902 (int)    : min=0 max=100000 step=1 default=0 value=0
               timeout_image_io 0x0098f903 (bool)   : default=0 value=0

What is wrong? what is modifying the device? how can i resolve this?

v4l2loopback version

0.12.5

kernel version

Linux dmz 5.4.0-200-generic #220-Ubuntu SMP Fri Sep 27 13:19:16 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux

OS Version

Ubuntu 20.04

Which CPU are you using?

amd64/x86_64 ("64bit Intel")

[umlaeute]

1. Please check with the latest release of v4l2loopback (at the time of writing this is 0.13.2)
2. If this doesn't help, please provide actual commands to reproduce the problem on a pristine machine (eg rather than "run the container" I would expect something like docker run --rm -ti alpine:latest bash

[GreatAg]

Thanks for the replay,
I run my container using this command:
docker run -d --device=/dev/video2 ubuntu:20:04
which i have chrome installed in that image and i want to use webcam in container.

[GreatAg]

also i checked the latest version and the problem still there.
This is really weird.

[umlaeute]

I run my container using this command:

that was really just an example.
i would need all commands you run, and I need know where you run each of them (within the container, or outside).

e.g. in your example there is no a producer anywhere.

[GreatAg]

You can take a look at kasm application (https://kasmweb.com/)
I am doing pretty much the same thing in my app
Also kasm using v4l2loopback

[umlaeute]

sorry, I don't think i will (find the time to) checkout kasm, just to reproduce this issue.

please try to provide a minimal reproducible example.