[alsa-devel] USB Audio device syncpipe error

Alex Lee alexlee188 at gmail.com
Mon Sep 13 16:42:40 CEST 2010

Clemens Ladisch <clemens <at> ladisch.de> writes:

> 6275 kson wrote:
> > Well I basically understand what is wrong.  Usbaudio is expecting the packet
> > size to be 4 and the value to be encoded as 16.16 because the device is
> > operating at high speed.  I made the change and my device now shows up
> > properly as an output device and playback works but the feedback polling
> > interval is incorrect.
> What interval do you expect in this situation, and what interval do you

Hi kson,

bInterval in HS is in terms of uFrame, ie 128us.  In FS it is in Frame, ie 1ms.

Also, the feedback endpoint may be using bRefresh instead of bInterval to 
determine the
 interval to check the feedback sample rate.

I'm also implementing the async iso OUT with feedback using UAC1 at HS right
 now so I'm 
following your posts :-)


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