Hi Pierre, On Wednesday 09 July 2008, MARTIN Pierre wrote: > Hello list people :) > > i have been posting about some issues i had a couple of monthes ago. > The company i'm working for was in the need of a system with 5 > webcams, able to shoot simultaneously "objects" from 5 different POVs. > The generated pictures are then used for 3D modeling. > > Big problem, the "object" is a horse, so the total time of shooting > has to be around 10 seconds, not more, because holding a horse still > for more than 10 seconds require super powers, which we don't have (Or > are too expensive, i dont know) :) > > So we bought 5 quickcam 9000 pro, since the required resolution to > have a find 3D mesh is 1600x1200. > > Actually, all the webcams are wired to a single USB hub, and a little > application i have coded handles a very simple queue when the user > presses the "shoot" button. > The application simply calls the uvccapture command, waits for it to > finish, stores the result, and starts uvccapture on the next camera (/ > dev/video0 / 1 / 2 / 3 / 4) and so on. > > The task takes around 18 seconds it's a bit too much. > > So i was wondering... Why not to use two USB hubs to wire the cameras, > 3 cameras on the first hub, two on the second, so the application will > be able to shoot two cams at the same time, then again, then the one > remaining? > > So today i coded this workflow on my application, /dev/video0 to /dev/ > video2 on the first hub, /dev/video3 and /dev/video4 on the other. > The goal was to shoot video0 / video 3 at the same time, then video1 / > video4 at the same time, then /dev/video3. > And i was very surprised to see that the system doesn't allows me > simultaneous requests to the driver. > > Is there any solution to that?
Logitech cameras don't support MJPEG compression for 1600x1200. Streaming such a high resolution in YUV requires a high bandwidth, and USB 2.0 doesn't provide enough bandwidth to stream from two 1600x1200 cameras at the same time. Logitech webcams are quite slow to initialise the first time you use them, but might be faster the second time your run your application if you don't disconnect the cameras. Could you please try that and let me know if it helps ? Best regards, Laurent Pinchart _______________________________________________ Linux-uvc-devel mailing list [email protected] https://lists.berlios.de/mailman/listinfo/linux-uvc-devel
