v4l2loopback webcam not detected

[Daniel Pocock]

I have a v4l2loopback setup from OBS Studio.  It works fine with
guvcview and Firefox (WebRTC)

Jami says "No camera detected"

Jami version 20210104.4.dda80df~ds1-1


$ v4l2-ctl -d /dev/video2 --all

Driver Info:
        Driver name      : v4l2 loopback
        Card type        : Dummy video device (0x0000)
        Bus info         : platform:v4l2loopback-000
        Driver version   : 4.19.132
        Capabilities     : 0x85208001
                Video Capture
                Video Memory-to-Memory
                Read/Write
                Streaming
                Extended Pix Format
                Device Capabilities
        Device Caps      : 0x85208001
                Video Capture
                Video Memory-to-Memory
                Read/Write
                Streaming
                Extended Pix Format
                Device Capabilities
Priority: 0
Video input : 0 (loopback: ok)
Format Video Capture:
        Width/Height      : 1280/720
        Pixel Format      : 'YUYV' (YUYV 4:2:2)
        Field             : None
        Bytes per Line    : 2560
        Size Image        : 1843200
        Colorspace        : sRGB
        Transfer Function : Default (maps to sRGB)
        YCbCr/HSV Encoding: Default (maps to ITU-R 601)
        Quantization      : Default (maps to Limited Range)
        Flags             :
Format Video Output:
        Width/Height      : 1280/720
        Pixel Format      : 'YUYV' (YUYV 4:2:2)
        Field             : None
        Bytes per Line    : 2560
        Size Image        : 1843200
        Colorspace        : sRGB
        Transfer Function : Default (maps to sRGB)
        YCbCr/HSV Encoding: Default (maps to ITU-R 601)
        Quantization      : Default (maps to Limited Range)
        Flags             :
Streaming Parameters Video Capture:
        Frames per second: 25.000 (25/1)
        Read buffers     : 8
Streaming Parameters Video Output:
        Frames per second: 25.000 (25/1)
        Write buffers    : 8

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