Hi Paul, > as much as I would like to see cheap USB webcam based stereo vision, I > have to agree with you that adherence to standard is crucial. In general > case we have to assume different values in device and host SOF counters. Do > you have means (bus analyzer) to test some UVC cameras to find out if these > counters have the same values?
There's an easier way. I just plugged two Logitech webcams. Their SOF counters seem to be synchronised. > Maybe all of them or most of them do. In such a case, it would be worthwhile > to pursue it further. Agreed, that would be interesting. Webcams with synchronised SOF counters could be marked as such in the driver. > UVC driver could use time stamps only for these devices. The driver should support timestamps for all UVC webcams. Devices which have a non-synchronised SOF counter would use the PTS/SCR values to handle clock drift. Other devices could be synchronised to the host clock. > I can provide you with at least one new UVC camera, which is not on official > list yet (V-Gear TalkCam MX6) for testing. Have you tested it ? Does it work ? If so, I can add it to the list on the website. Please provide me with the device USB descriptors. > There seems to be a way to get host system time at SOF Token generation. > Chapter 6.3 of Open Host Controller Interface Specification for USB > describes StartOfFrame interrupt event, which could be used for this > purpose. That won't work for EHCI controllers (not sure about UHCI). We need to find something else. Best regards, Laurent Pinchart _______________________________________________ Linux-uvc-devel mailing list Linux-uvc-devel@lists.berlios.de https://lists.berlios.de/mailman/listinfo/linux-uvc-devel
