Am Sonntag, den 06.03.2011, 12:47 +0000 schrieb Paulo Assis: > Hi, > please check this link: > http://forums.quickcamteam.net/showthread.php?tid=1305 > with a little fix to the previous patch the camera seems to work fine > with at least two units streaming at the same time. > > I can't send an updated patch right now since my adsl connection is on > the slow side at the moment, and cloning the uvc git repo would take > several hours. > When/if I manage to get this done I'll post the full patch.
You do not need to, i send a patch set to work with this problem, Laurent need to think about it :D > Regards, > Paulo > > 2011/3/6 Laurent Pinchart <laurent.pinch...@ideasonboard.com>: > > Hi Philip, > > > > On Sunday 20 February 2011 21:57:24 Philip Gladstone wrote: > >> I attached two C910s to a small linux box, and ran into the 'Failed to > >> submit URB' problem. > >> > >> When I look at the descriptors for this camera, I think I understand the > >> problem. I'm capturing at 5 Mpixels and I'm trying two cameras. > >> > >> VideoStreaming Interface Descriptor: > >> bLength 38 > >> bDescriptorType 36 > >> bDescriptorSubtype 7 (FRAME_MJPEG) > >> bFrameIndex 28 > >> bmCapabilities 0x01 > >> Still image supported > >> wWidth 2592 > >> wHeight 1944 > >> dwMinBitRate 403107840 > >> dwMaxBitRate 806215680 > >> dwMaxVideoFrameBufferSize 10077696 > >> dwDefaultFrameInterval 1000000 > >> bFrameIntervalType 3 > >> dwFrameInterval( 0) 1000000 > >> dwFrameInterval( 1) 1333333 > >> dwFrameInterval( 2) 2000000 > >> > >> The video frame size is set to 10Mb. This is surprisingly large as > >> actual frames captured with MJPEG on this camera are typically 500kb or > >> less. When I checked the descriptor for the uncompressed version of the > >> same frame, it came back with the same value of dwMaxVideoFrameBufferSize > >> (effectively 16 bits per pixel). The values for min/max bit rate are > >> (correctly) calculated from the frame intervals and the buffer size. > > > > The uvcvideo driver doesn't use the dwMaxVideoFrameBufferSize field to > > compute > > the required bandwidth but queries the device at runtime instead. > > > > You can enable the UVC_TRACE_VIDEO trace flag to get the driver to print the > > bandwidth requested by the device to the kernel log. > > > >> Typical JPEG compression gets down to 1 bit per pixel, and 2 bits is > >> very unusual. > >> > >> What I want to know is what the impact would be of defining a new QUIRK > >> that overrode the frame buffer size for compressed frames and calculated > >> them at (say) 2 bits per pixel? > >> > >> Do other webcams get this right? > > > > You would be surprised by how many webcams get things wrong. > > > > -- > > Regards, > > > > Laurent Pinchart > > _______________________________________________ > > Linux-uvc-devel mailing list > > Linux-uvc-devel@lists.berlios.de > > https://lists.berlios.de/mailman/listinfo/linux-uvc-devel > > > _______________________________________________ > Linux-uvc-devel mailing list > Linux-uvc-devel@lists.berlios.de > https://lists.berlios.de/mailman/listinfo/linux-uvc-devel _______________________________________________ Linux-uvc-devel mailing list Linux-uvc-devel@lists.berlios.de https://lists.berlios.de/mailman/listinfo/linux-uvc-devel
