On Fri, Aug 31, 2012 at 11:56 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > Clemens and Laurent (and anyone else who's interested): > > How should the lower USB layers handle delays in transferring > isochronous data? I'm asking you because the most common usages of > isochronous transfers are for audio and video. > > Here's an example to illustrate what I mean. Typically an audio or > video driver will keep a queue of around 10 ms of data submitted to an > isochronous endpoint. I have seen reports from users where URB > completion interrupts were delayed by as much as 50 ms. In one case > the delay was caused by a bug in a wireless drivers that left > interrupts disabled; in another case the cause was unknown -- it might > have been a hardware problem. At any rate, when this happens the > endpoint's queue drains completely. > > Clearly this will cause a glitch in the data stream. The question is: > What should we do to recover and re-synchronize? > How about effectively increasing the queue length from 10ms to 50ms (max anticipated latency) ? -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
