-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Laurent Pinchart wrote: > That's bad. The USB EHCI driver will reject 2x 3072 bytes per microframe as > exceeding the available bandwidth.
Yep, I suspected something like that ... > I suppose you'll object that the cameras work on Windows, so I'll try to > address that :-) Thank you :) > > I see three possible reasons why Windows would stream video from both cameras > at the same time. > > - The Windows UVC driver might query the cameras slightly differently and > receive a different bandwidth. A USB sniffer would help confirm or infirm > this explanation. I can check this if I manage to get a sniffer to work. I will report back once that far. > > - The Windows UVC driver might ignore the requested bandwidth and compute a > value itself. > > - Windows might accept 2x 3072 bytes per microframe. I seem to remember this > might be the case, and that that behaviour is buggy according to the USB 2.0 > spec. You would have to contact the linux-usb mailing list for more > information on that. Hard to say which one is correct. It could be even both - Windows accepts the value (doesn't report error) and the driver does some kind of black magic afterwards to get things actually working. I am getting different resolutions offered on Windows than on Linux and also the camera seems to run at a lower framerate if both cameras are streaming. I didn't try to measure it, but the stereo output looks like ~10fps or so. It could be a software issue as well, though. The documentation is also cautioning to plug the device ideally to a separate host and not to use the USB connectors on the front panel - they assume that those are not full-featured. So it could be indeed a marginal design. > It would be helpful if you could capture all USB control traffic from device > enumeration to video streaming using a USB analyser (a software one will do). > It would show what bandwidth the device requests, and what bandwidth the > Windows UVC driver selects. As I said above, I will try to get a sniffer working and will report back once that far. Regards (and thanks), Jan -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) Comment: Using GnuPG with Mandriva - http://enigmail.mozdev.org iD8DBQFJhz2+n11XseNj94gRAlm+AKDOTMtUwPvAFW4sqLmLc+DhGzcXvgCeIuJP /Pq16p2jarKlLMQdVtCJmbI= =NsvL -----END PGP SIGNATURE----- _______________________________________________ Linux-uvc-devel mailing list Linux-uvc-devel@lists.berlios.de https://lists.berlios.de/mailman/listinfo/linux-uvc-devel
