Can we use a couple of threads to do the call to write()? That way the
thread can block on the write() call but we can return to CoreAudio.
Mark
> -----Original Message-----
> From: Rhoads Hollowell [mailto:email@hidden]
> Sent: Friday, March 09, 2007 12:00 PM
> To: Mark Cookson
> Cc: email@hidden
> Subject: Re: Write takes too long to return
>
> Hey Mark,
>
> We have a bug on this already, and we are looking at what we can do
> to fix it without breaking anything else.
>
> It has to do with the fact that the port in question shares a Full
> Speed controller with the internal keyboard/trackpad, which gets
> suspended when it is not being used to save power.
>
> You can mitigate this most easily by using a different port.
>
> You can also insert a High Speed hub, which uses a different
controller.
>
> Other than that, just know that we are aware of the issue and are
> working on a solution.
>
> ----------------------------
> Rhoads Hollowell
> USB Software Team
> Apple Inc.
>
>
> On Mar 9, 2007, at 10:15 AM, Mark Cookson wrote:
>
> > We're streaming isoc audio on a MacBook or MacBook Pro and getting
> > occasional dropouts of audio that we've traced to being stalled for
> > about 10-20ms in a call to pipe->Write().
> >
> >
> >
> > Also, it appears that the problem only happens on the rearmost USB
> > port on the MacBook, and it only happens after you press a key
> > after you haven't pressed any keys for a while.The question is,
> > what can we do to avoid this? Are we somehow holding a lock that
> > IOUSBFamily needs? Could we change our order of operations to fix
> > this? Should we not be requesting an interrupt with every frame
> > (low latency isoc with updateFrequency = 1)? The fact that it only
> > happens on one MacBook port is very suspicious and makes me worried
> > that we can't actually fix it on our end, but are there steps we
> > can take to mitigate its effects?
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