Re: Synchronizing with the actual USB device audio clock
Re: Synchronizing with the actual USB device audio clock
- Subject: Re: Synchronizing with the actual USB device audio clock
- From: Jeff Moore <email@hidden>
- Date: Wed, 21 Dec 2005 16:53:27 -0800
On Dec 21, 2005, at 4:47 PM, Markus Medau wrote:
Yes. As I understand it, the neither the USB spec nor the Audio Class
spec provide for expressing the device's sample clock to the host. I
think that with adaptive devices, they can provide feedback to the
host to give the host hints about going faster or slower, but I don't
recall if this is for host->device communication or just just for
device->host communication. I'd have to ask the guys working on the
USB driver to be sure.
Output:
- synchronous: samplerate follows USB clock
- adaptive: hardware follows computer (host)
- asynchronous: feedback pipe (independant samplerate)
Input:
- synchronous: samplerate follows USB clock
- adaptive: feedback pipe (independant samplerate)
- asynchronous: computer (host) follows hardware
Thanks for the info!
Jeff, could you please ask someone to check out our bugreport #4105986
from May, 3rd? This is about probs with asynchronous output making our
USB2 Audio solutions being Windows XP only in class compliant mode.
All needed for reproduction is a digital output at the audio source
and an
Apple/Emagic A26. Of course we can also supply hardware to
demonstrate it
if needed. Thanks alot.
The A26 has some funny clock issues as well as has the problem of not
being sold anymore. You would likely get more action on this bug if
you were able to demonstrate it with some other piece of common
hardware so that the bug can be seen a clearly not having to do with
the A26 but is an issue with the USB Audio class driver.
--
Jeff Moore
Core Audio
Apple
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