Hi Michael, > I'm having some problems reading from /dev/video0 when using my Logitech > QuickCam Orbit MP camera. I'm using an ubuntu 2.6.15-28-386 kernel. > > At module insertion time, with trace set to 15, I see the following in > dmesg: > > [17179739.156000] Linux video capture interface: v1.00 > [17179739.172000] uvcvideo: Adding mapping Brightness to control > 00000000-0000-0000-0000-000000000101/2. [17179739.172000] uvcvideo: Adding > mapping Contrast to control 00000000-0000-0000-0000-000000000101/3. > [17179739.172000] uvcvideo: Adding mapping Hue to control > 00000000-0000-0000-0000-000000000101/6. [17179739.172000] uvcvideo: Adding > mapping Saturation to control 00000000-0000-0000-0000-000000000101/7. > [17179739.172000] uvcvideo: Adding mapping Sharpness to control > 00000000-0000-0000-0000-000000000101/8. [17179739.172000] uvcvideo: Adding > mapping Gamma to control 00000000-0000-0000-0000-000000000101/9. > [17179739.172000] uvcvideo: Adding mapping Backlight Compensation to > control 00000000-0000-0000-0000-000000000101/1. [17179739.172000] uvcvideo: > Adding mapping Gain to control 00000000-0000-0000-0000-000000000101/4. > [17179739.172000] uvcvideo: Adding mapping Power Line Frequency to control > 00000000-0000-0000-0000-000000000101/5. [17179739.172000] uvcvideo: Adding > mapping Hue, Auto to control 00000000-0000-0000-0000-000000000101/16. > [17179739.172000] uvcvideo: Adding mapping Pan (relative) to control > 63610682-5070-49ab-b8cc-b3855e8d2256/1. [17179739.172000] uvcvideo: Adding > mapping Tilt (relative) to control 63610682-5070-49ab-b8cc-b3855e8d2256/1. > [17179739.172000] uvcvideo: Adding mapping Pan/Tilt (reset) to control > 63610682-5070-49ab-b8cc-b3855e8d2256/2. [17179739.172000] uvcvideo: Adding > mapping Exposure, Auto to control 00000000-0000-0000-0000-000000000001/2. > [17179739.172000] uvcvideo: Adding mapping Exposure (Absolute) to control > 00000000-0000-0000-0000-000000000001/4. [17179739.172000] uvcvideo: Adding > mapping White Balance Temperature, Auto to control > 00000000-0000-0000-0000-000000000101/11. [17179739.172000] uvcvideo: Adding > mapping White Balance Temperature to control > 00000000-0000-0000-0000-000000000101/10. [17179739.172000] usbcore: > registered new driver uvcvideo > [17179739.172000] USB Video Class driver (v0.1.0) > > And when I plug in the USB cable, I see: > > [17179760.888000] usb 5-7: new high speed USB device using ehci_hcd and > address 4 [17179761.196000] uvcvideo: Probing known UVC device 7 > (046d:08c2) [17179761.200000] uvcvideo: Found format MJPEG. > [17179761.200000] uvcvideo: - 160x120 (30.0 fps) > [17179761.200000] uvcvideo: - 176x144 (30.0 fps) > [17179761.200000] uvcvideo: - 320x240 (15.0 fps) > [17179761.200000] uvcvideo: - 352x288 (30.0 fps) > [17179761.200000] uvcvideo: - 432x240 (30.0 fps) > [17179761.200000] uvcvideo: - 480x360 (30.0 fps) > [17179761.200000] uvcvideo: - 512x288 (30.0 fps) > [17179761.200000] uvcvideo: - 640x360 (30.0 fps) > [17179761.200000] uvcvideo: - 640x480 (15.0 fps) > [17179761.200000] uvcvideo: - 704x576 (15.0 fps) > [17179761.200000] uvcvideo: - 864x480 (15.0 fps) > [17179761.200000] uvcvideo: - 960x720 (15.0 fps) > [17179761.200000] uvcvideo: Found format Uncompressed. > [17179761.200000] uvcvideo: - 1024x576 (10.0 fps) > [17179761.200000] uvcvideo: - 1280x960 (7.5 fps) > [17179761.200000] uvcvideo: Found a Status endpoint (addr 87). > [17179761.200000] uvcvideo: Found UVC 1.00 device <unnamed> (046d:08c2) > [17179761.200000] uvcvideo: Added control > 00000000-0000-0000-0000-000000000101/2 to device 7 entity 2 > [17179761.200000] uvcvideo: Added control > 00000000-0000-0000-0000-000000000101/3 to device 7 entity 2 > [17179761.200000] uvcvideo: Added control > 00000000-0000-0000-0000-000000000101/7 to device 7 entity 2 > [17179761.200000] uvcvideo: Added control > 00000000-0000-0000-0000-000000000101/8 to device 7 entity 2 > [17179761.200000] uvcvideo: Added control > 00000000-0000-0000-0000-000000000101/9 to device 7 entity 2 > [17179761.200000] uvcvideo: Added control > 00000000-0000-0000-0000-000000000101/1 to device 7 entity 2 > [17179761.200000] uvcvideo: Added control > 00000000-0000-0000-0000-000000000101/4 to device 7 entity 2 > [17179761.200000] uvcvideo: Added control > 00000000-0000-0000-0000-000000000101/5 to device 7 entity 2 > [17179761.200000] uvcvideo: Added control > 63610682-5070-49ab-b8cc-b3855e8d2256/1 to device 7 entity 9 > [17179761.200000] uvcvideo: Added control > 63610682-5070-49ab-b8cc-b3855e8d2256/2 to device 7 entity 9 > [17179761.200000] uvcvideo: Added control > 00000000-0000-0000-0000-000000000001/2 to device 7 entity 1 > [17179761.200000] uvcvideo: Added control > 00000000-0000-0000-0000-000000000001/4 to device 7 entity 1 > [17179761.200000] uvcvideo: Added control > 00000000-0000-0000-0000-000000000101/11 to device 7 entity 2 > [17179761.200000] uvcvideo: Added control > 00000000-0000-0000-0000-000000000101/10 to device 7 entity 2 > [17179761.200000] uvcvideo: Scanning UVC chain: OT 5 (-> 8 10 9) <- Unit 4 > <- Unit 3 <- Unit 2 <- IT 1 [17179761.200000] uvcvideo: Found a valid video > chain (1 -> 5). [17179761.212000] uvcvideo: UVC device initialized. > [17179762.384000] 4:3:1: cannot set freq 0 to ep 0x86 > [17179763.384000] 4:3:2: cannot set freq 0 to ep 0x86 > [17179764.388000] 4:3:3: cannot get freq at ep 0x86 > [17179764.468000] usbcore: registered new driver snd-usb-audio > > As far as I can tell the above looks correct, and once plugged in the > /dev/video0 device is created by udev. However, when I go to read from > the /dev/video0 device, it fails: > > [EMAIL PROTECTED] ~]$ ls -l /dev/video0 > crw-rw---- 1 root video 81, 0 Mar 23 13:23 /dev/video0 > > [EMAIL PROTECTED] ~]$ cat /dev/video0 > /tmp/foo.mpg > cat: /dev/video0: No such device > > No additional lines appear in dmesg after attempting to read from > /dev/video0. > > Does anyone know what the problem might be? I have two cameras of > the same make and model, but ran into the same problem with both.
The Linux UVC driver doesn't support reading directly from the device (yet). Only the streaming I/O method (using mmap) is supported. You can test your webcam with luvcview. Cheers, Laurent Pinchart _______________________________________________ Linux-uvc-devel mailing list Linux-uvc-devel@lists.berlios.de https://lists.berlios.de/mailman/listinfo/linux-uvc-devel
