Hi Ben, On Wednesday 03 October 2007, Ben Lau wrote: > Hi, > > I have VGear Talkcam MX6 EZ and Talkcam MX6 AF. In low light > environment, both of the webcam drop frame rate from 25fps to 12fps > (or even lower) automatically. Can I forbid the camera to drop frame > through the UVC driver?
I'm afraid not. Your webcams default to automatic exposure mode, which is allowed to lower the frame rate in low light conditions. You would need to switch to manual exposure mode, but that doesn't seem to be possible with the VGear Talkcam MX6. To confirm this (or to prove me wrong :-)), have a look at the USB descriptors with lsusb -v (usbutils 0.72 or newer). If the Input Terminal has "Auto-Exposure Mode" and "Exposure Time (Absolute)" controls, then you will be able to switch to manual exposure. Otherwise, you're stuck with lower frame rates. > p.s Do the Creative Live! Optia has the same problem? I'm not sure if the webcam will lower the frame rate, but it supports manual exposure so you should be safe. > The available control of the camera: > > $ luvcview -f yuv -l > luvcview version 0.2.1 > Video driver: x11 > A window manager is available > video /dev/video0 > Available controls of device 'Camera 1' (Type 1=Integer 2=Boolean > 3=Menu 4=Button) > V4L2_CID_BASE (predefined controls): > index:9963776 name:Brightness type:1 > min:-128 max:127 step:1 def:0 now:0 > index:9963777 name:Contrast type:1 min:0 > max:100 step:1 def:0 now:0 > index:9963778 name:Saturation type:1 min:0 > max:100 step:1 def:0 now:0 > index:9963779 name:Hue type:1 min:-40 > max:40 step:1 def:0 now:0 > index:9963792 name:Gamma type:1 min:1 > max:100 step:1 def:1 now:1 > V4L2_CID_PRIVATE_BASE (driver specific controls): > index:134217728 name:Backlight Compensation type:1 min:0 > max:1 step:1 def:0 now:0 > index:134217729 name:Power Line Frequency type:3 min:0 > max:2 step:1 def:1 now:1 > Menu items: > index:0 name:Disabled > index:1 name:50 Hz > index:2 name:60 Hz > index:134217730 name:Sharpness type:1 min:0 > max:100 step:1 def:0 now:0 Best regards, Laurent Pinchart _______________________________________________ Linux-uvc-devel mailing list [email protected] https://lists.berlios.de/mailman/listinfo/linux-uvc-devel
