Hi Chris, On Thursday 02 September 2010 04:32:11 Chris wrote: > Hi, > > I am using an embedded device and wish to get at least 2 USB webcams > working at one time. > I have been playing with the: > bandwidth = stream->ctrl.dwMaxPayloadTransferSize; > > And changed it to a variety of numbers finding that setting it to 768 > works: bandwidth = 768; > > With the above setting I can get 4 webcams working at 320x240 at 1 fps. > > I have tried: 768, 1024, 1536, 1792, 2048 (can run one cam at 640x480 only), > 3072 > The only way I can get multiple cams at any resolution is at 768 and only > 320x240. > Ideally we want to be able to run up to 4 cams at 640x480. > > I was wondering if there are any other ways to achieve this? > I see there are a few posts this year around this topic by Laurent.
The camera reports the bandwidth requirements and the driver tries to fulfill them. You haven't reported the camera model and the frame formats, so I can only assume that your camera outputs uncompressed YUV images. 2 cameras streaming uncompressed video at 640x480 will exceed the maximum USB bandwidth. You have several options to achieve 4 simultaneous VGA streams: - switch to MJPEG if your cameras supports hardware compression - use multiple USB host controllers (on add-on PCI boards for instance) - use cameras that can buffer whole images and use a lower frame rate (this is theoretical only, I don't know of any such camera in the mainstream market). -- Regards, Laurent Pinchart _______________________________________________ Linux-uvc-devel mailing list [email protected] https://lists.berlios.de/mailman/listinfo/linux-uvc-devel
