(keep it on the mailing list, please; back on there now)
On Sun, 11 Sep 2005 20:17:01 -0700 (PDT) jatan wrote: > > Bandwidth allocation is a kernel config option under > > the main USB > > config heading. I would expect (but don't know) > > that most distros > > do not enable it. It's mostly useless and not > > implemented at the > > correct level. > > > > Are you connecting the 3 webcams to only one USB > > host > > controller? I can see how that might create a > > bandwidth > > problem, but linux-usb's bandwidth allocation > > probably > > isn't the problem so much as only one host > > controller is, > > so if you are using only one host controller (check > > 'lspci' output for USB host controllers), you could > > consider > > adding another host controller (e.g., a PCI card > > that costs > > maybe US$20.00). > > 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? --- ~Randy ------------------------------------------------------- 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
