Hi Paulo, On Wednesday 03 June 2009 00:04:23 Paulo Assis wrote: > Hi, > so here are my findings (using a sphere AF): > > I'm now disabling the video stream and re-queueing the buffers, this > enables VIDIOC_S_JPEGCOMP > > below is what I'm getting from the driver and the corresponding log entry > from dmesg: > > setting quality to 60 => > > VIDIOC_G_COMP: > quality: 60 > APPn: 0 > APP_len: 0 > APP_data: > COM_len: 0 > COM_data: > jpeg_markers: 0x10 > > "dmesg (with trace=15)" > [ 9993.399812] uvcvideo: Setting jpeg quality to 6000. > > setting quality to 80 => > > VIDIOC_G_COMP: > quality: 80 > APPn: 0 > APP_len: 0 > APP_data: > COM_len: 0 > COM_data: > jpeg_markers: 0x10 > > "dmesg (with trace=15)" > [10001.869273] uvcvideo: Setting jpeg quality to 8200. > > In any case the video frames don't change their quality, so I guess the > camera is not handling this the correct way,
I haven't seen any visual difference either between Q=20 and Q=100 on my Logitech Quickcam Pro for Notebooks. However, the average frame size was ~24k for Q=20 and ~28k for Q=100, so I guess there's still a difference. > I can't also understand the values seen in dmesg, is there any reason > special reason for this ? The quality range in the UVC specification is [0, 10000]. While the V4L2 specification doesn't mention any specific range, most users are familiar with the [0, 100] range. I thus convert between the two ranges in the driver. Moreover, the requested quality value is passed to the hardware which is free to modify it. This is probably why you get 8200 when you ask for 8000. Best regards, Laurent Pinchart _______________________________________________ Linux-uvc-devel mailing list [email protected] https://lists.berlios.de/mailman/listinfo/linux-uvc-devel
