Package: linux
Version: 6.12.96+deb13-amd64
Control: affects -1 pipewire
Severity: wishlist
The hardware of the tested USB camera is as follows:
# lsusb -v -d 046d:092f | egrep -i "idProduct|idVendor"
idVendor 0x046d Logitech, Inc.
idProduct 0x092f QuickCam Express Plus
Windows 11 says it's “Logitech Quickcam Express/Go”.
The camera is handled by the gspca_spca561 driver:
# readlink -f /sys/class/video4linux/video1/device/driver
/sys/bus/usb/drivers/spca561
Problem: The driver exposes only S561 (320×240 and 352×288) and GBRG (160×120
and 176×144) formats:
$ v4l2-ctl -d /dev/video1 --all --list-formats-ext
Driver Info:
Driver name : spca561
Card type : Camera
Bus info : usb-0000:00:14.0-5.1
Driver version : 6.12.96
Capabilities : 0x85200001
Video Capture
Read/Write
Streaming
Extended Pix Format
Device Capabilities
Device Caps : 0x05200001
Video Capture
Read/Write
Streaming
Extended Pix Format
Priority: 2
Video input : 0 (spca561: ok)
Format Video Capture:
Width/Height : 352/288
Pixel Format : 'S561' (GSPCA SPCA561)
Field : None
Bytes per Line : 352
Size Image : 50688
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: invalid (0/0)
Read buffers : 2
User Controls
brightness 0x00980900 (int) : min=-128 max=127 step=1 default=0 value=0 flags=slider
hue 0x00980903 (int) : min=1 max=127 step=1
default=64 value=64 flags=slider
exposure 0x00980911 (int) : min=1 max=2372 step=1
default=700 value=700
gain 0x00980913 (int) : min=0 max=255 step=1
default=63 value=70
ioctl: VIDIOC_ENUM_FMT
Type: Video Capture
[0]: 'S561' (GSPCA SPCA561, compressed)
Size: Discrete 320x240
Size: Discrete 352x288
[1]: 'GBRG' (8-bit Bayer GBGB/RGRG)
Size: Discrete 160x120
Size: Discrete 176x144
Modern PipeWire camera applications cannot use the camera directly. Snapshot
doesn't detect the camera, and Firefox and Chromium see the camera but cannot
obtain a usable video stream.
The only workaround known to me is a cumbersome multistep process requiring
root privileges:
1) Determine the /dev/video… device corresponding to the camera from the output
of `v4l2-ctl --list-devices`. In our test, this is /dev/video1, and it's
subject to change (say, at boot or when re-plugging).
2) Create a loopback device:
$ sudo modprobe -r v4l2loopback
$ sudo modprobe v4l2loopback video_nr=10 card_label="QuickCam Express
(converted)" exclusive_caps=1
3) Convert the stream and feed it into the loopback device in a new xterm:
$ LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libv4l/v4l2convert.so ffmpeg -f v4l2
-video_size 352x288 -i /dev/video1 -f v4l2 /dev/video10
Keep the process running as long as you need the camera (to quit, hit “q”).
The maximal resolution was taken from the output of `v4l2-ctl -d /dev/video1
--list-formats-ext`.
4) Restart PipeWire components:
$ systemctl --user restart pipewire pipewire-pulse wireplumber
5) Applications can then use the virtual camera exposed through /dev/video10.
Tests:
$ snapshot
$ ffplay -f v4l2 /dev/video10
$ firefox https://webcamtests.com
$ chromium
https://webrtc.github.io/samples/src/content/getusermedia/resolution
Wish:
Please consider exposing at least one commonly supported standard V4L2 pixel
format in addition to the existing S561 and GBRG formats. Examples include YUYV
or another standard format directly usable by modern PipeWire/WebRTC camera
applications. This would allow the camera to be used directly by applications
such as Snapshot, Firefox, and Chromium without requiring an ffmpeg +
v4l2loopback conversion pipeline.
