[cpia] usb errors using cpia/gqcam

[Peter Pregler]

On Wed, Nov 22, 2000 at 11:41:30AM -0500, Johannes Erdfelt wrote:
> 
> You can't use 2 cpia cameras on the same bus because there isn't enough
> bandwidth. The open failing is the USB core telling you that.

> It works on 2 busses because each bus has it's own bandwidth.

A bandwidth traffic shaper was what I suspected. Thanx for the info.
And of cause this answers the question for all guys that connect
several cameras to a bus and had problems. Make sure that the
open/close of the camera is serialized by software means.

Hmmm, thinking of the following scenario I see no real need for such a
hard limit. Imagine that you have ten webcams that take a picture
every 10 seconds. It would be fine if the usb-system would allow the
user to issue the requests and deliver the data with a unspecified bit
rate (comparable to ATM-UBR ;). Or is the isochronous mode for USB we
use (AFAIK) just capable of handling constant bit rate. Sorry for
asking such simple questions but I am not that familiar with the
usb-spec. In other words, is it possible to modify the cpia-driver to
allocate and use the usb-bus in a less rigid way?

Greetings, Peter

-- 
I will not waste chalk. --Bart Simpson at the blackboard
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