(back on the mailing list)
On Sun, 11 Sep 2005 22:30:08 -0700 (PDT) jatan wrote: > > > > > > Thanx for replying. Ya, I am connecting 3 webcams > > to > > > single usb host controller. I am using usb hub to > > > connect rest 2 out of 3 webcams. usb documentation > > > says that one can attach 127 max devices to a > > single > > > machine. so i started by assuming that things > > should > > > work without any problem. but it isnt. > > > i was looking at zoneminder utility > > > (http://www.zoneminder.com) and found following in > > its > > > readme file. > > > > 127 includes hubs. Lots of them would need to be > > low-speed > > devices for it to all work out OK. I've connected > > around > > 25 (or 28/29) devices to one USB host controller at > > a > > USB plugfest many years ago. > > > > > USB bus problems: > > > If you have multiple USB cameras on one bus then > > it > > > can appear as if ZoneMinder is causing your > > cameras to > > > fail. This is because the bandwidth available to > > > cameras is limited by the fairly low USB speed. In > > > order to use more than one USB camera with > > ZoneMinder > > > (or any application) you will need to inform the > > > driver that there are other cameras requiring > > > bandwidth. This is usually done with a simple > > module > > > option. Examples are usb_alt=<n> for the OV511 > > driver > > > and cams=<n> for CPIA etc. Check your driver > > > documentation for more details. Be aware however > > that > > > sharing cameras in this way on one bus will also > > limit > > > the capture rate due to the reduced bandwidth. > > > > So some version(s) of the camera drivers do some > > kind of > > bandwidth adjustments themselves. In 2.6.13, OV511 > > accepts a "cams" parameter for number of cameras and > > then > > adjusts frame rates. I don't see anything like > > <cams> > > for the CPIA driver. > > > > What kernel version are you using? > > i am using 2.6.11.1-35 Fedora Core 3. And my webcams > are Logitech Quickcam pro 4000. Actually, tt will be > enough if I am able to grab pics from three webcams at > somewht lower framerate instead of streaming all > webcams simultaneously. Is it possible that at single > time I allocate all resources to any one of three > cameras and do this in a loop for all of them? As long as they are not streaming, but just taking snapshots, that should be feasible in theory. I don't know if anyone has proven that yet or not. --- ~Randy You can't do anything without having to do something else first. -- Belefant's Law ------------------------------------------------------- SF.Net email is Sponsored by the Better Software Conference & EXPO September 19-22, 2005 * San Francisco, CA * Development Lifecycle Practices Agile & Plan-Driven Development * Managing Projects & Teams * Testing & QA Security * Process Improvement & Measurement * http://www.sqe.com/bsce5sf _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
