Hi Cesar, On Tuesday 23 February 2010 01:48:10 Cesar Maciel wrote: > Hello, > > I am trying to capture from a webcam with a fixed frame rate. I am using > ffmpeg (svn revision 21498) with the following options: > > > ./ffmpeg -y -t 00:01:00 -f video4linux2 -r 30 -s 352x288 -i > /dev/video0 -vcodec msmpeg4v2 -f avi -r 30 video.avi > > > I used two webcams where uvcvideo shows being capable of 352x288 at > 30fps. For some reason, ffmpeg cannot keep the input frame rate, and it > starts to go down. There are processing resources available in the > system (Ubuntu Karmic 9.10, and also Voyage Linux 0.62 (Debian-based). I > have tried specifying the qscale option, but it did not make any > difference. Also, both cameras can output raw and mjpeg, but it also did > not make a difference.
Have you tried disabling auto-exposure ? Most cameras adjust the frame rate based on lightning conditions. > I have updated uvc on Karmic to the version available as a gzip file on > the official website. dmesg shows tons of > > uvcvideo: Dropping payload (out of sync). > > and every now and then: > > [28339.492016] uvcvideo: uvc_v4l2_ioctl(VIDIOC_QBUF) > [28339.492022] uvcvideo: Queuing buffer 30. > [28339.492030] uvcvideo: uvc_v4l2_ioctl(VIDIOC_DQBUF) > > > for both cameras. On Voyage Linux (kernel 2.6.30), it shows several msgs > like the following ones > > [26440.191029] uvcvideo: Queuing buffer 3. > [26440.191405] uvcvideo: uvc_v4l2_ioctl(VIDIOC_DQBUF) > [26440.201496] uvcvideo: uvc_v4l2_ioctl(VIDIOC_DQBUF) > [26440.211579] uvcvideo: uvc_v4l2_ioctl(VIDIOC_DQBUF) > [26440.221661] uvcvideo: uvc_v4l2_ioctl(VIDIOC_DQBUF) > [26440.230034] uvcvideo: Frame complete (EOF found). > [26440.231743] uvcvideo: uvc_v4l2_ioctl(VIDIOC_DQBUF) > [26440.231753] uvcvideo: Dequeuing buffer 4 (3, 14800 bytes). > [26440.249905] uvcvideo: uvc_v4l2_ioctl(VIDIOC_QBUF) > [26440.249921] uvcvideo: Queuing buffer 4. > [26440.249950] uvcvideo: uvc_v4l2_ioctl(VIDIOC_DQBUF) > > Cameras are Microsoft NX-3000 and Genius eFace 1325R > > Does anyone have an idea, or need more info? -- Regards, Laurent Pinchart _______________________________________________ Linux-uvc-devel mailing list Linux-uvc-devel@lists.berlios.de https://lists.berlios.de/mailman/listinfo/linux-uvc-devel
