The first open has:
```
[17047.368576] v4l2-loopback[1992]: opened dev:00000000c093a43d with
image:0000000000000000
[17047.368577]
/var/lib/dkms/v4l2loopback/0.12.5/build/v4l2loopback.c:1993[v4l2_loopback_open]
[17047.368582] video10: VIDIOC_QUERYCAP: driver=v4l2 loopback, card=OBS Video
Source, bus=platform:v4l2loopback-000, version=0x00050f07, capabilities=0x
85200002, device_caps=0x05200002
```
The second open has:
```
[17091.427287]
/var/lib/dkms/v4l2loopback/0.12.5/build/v4l2loopback.c:1964[v4l2_loopback_open]
[17091.427292] v4l2-loopback[1992]: opened dev:00000000c093a43d with
image:0000000000000000
[17091.427293]
/var/lib/dkms/v4l2loopback/0.12.5/build/v4l2loopback.c:1993[v4l2_loopback_open]
[17091.427297] video10: VIDIOC_QUERYCAP: driver=v4l2 loopback, card=OBS Video
Source, bus=platform:v4l2loopback-000, version=0x00050f07,
capabilities=0x85200000, device_caps=0x05200000
[17091.427304] video10: VIDIOC_G_FMT: error -22: type=vid-out,
width=4294966992, height=4294967295, pixelformat=.... little-endian
(0x00000000), field=any, bytesperline=1401200640, sizeimage=4288352138,
colorspace=-744513136, flags=0xfffffed0, ycbcr_enc=0, quantization=0,
xfer_func=0
```
As indicated in the capabilities field returned from the VIDIOC_QUERYCAP
call, 0x85200000 means no V4L2_CAP_VIDEO_CAPTURE(0x01) neither
V4L2_CAP_VIDEO_OUTPUT(0x02) is set. And since it reports neither, kernel
`check_fmt` in "drivers/media/v4l2-core/v4l2-ioctl.c" will evaluate
variable is_vid to false, and therefore returns -EINVAL.
This is a direct result from
https://github.com/umlaeute/v4l2loopback/commit/9a77eb6 merged in
https://github.com/umlaeute/v4l2loopback/pull/415.
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https://bugs.launchpad.net/bugs/1946660
Title:
Ubuntu port of v4l2loopback doesn't behave the same as official port
(v0.12.5)
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