[alsa-devel] USB Audio device syncpipe error

Clemens Ladisch clemens at ladisch.de
Fri Sep 10 09:01:32 CEST 2010

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
actually get?

> Since the feedback endpoint descriptor is not class specific I can see why
> one would expect it to be a usb 2.0 standard endpoint descriptor,

Yes, the UAC 1.0 spec cannot override the USB spec in this regard.

> however, that would mean I should also change my other audio
> streaming endpoint descriptors.

Which other descriptors?  AFAICS, the only other thing that is affected
by high-speed is the packet size and format of the sync endpoint.


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