On Fri, Aug 31, 2012 at 11:56 PM, Alan Stern <st...@rowland.harvard.edu> 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) ?
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