[alsa-devel] OSX Core Audio ASYNC OUT with rate feedback format ?

[Alex]

Alex <lee188 <at> singnet.com.sg> writes:

> 
> Hi Daniel et al,
> 
> I have successfully interfaced the sdr-widget with Linux alsa-driver
>  for ASYNC 
> OUT with rate feedback.  Found out after much trial
>  and error and reading of the 
> usbaudio alsa-driver source code that you are
>  using 12.13 as the format for the 
> feedback rate !!!  I was trying with 10.14 (UAC1 v1.2 specs
> , I think) in 3 bytes, 
> and 16.16 (USB 2.0) in 4 bytes for quite a number of days
>  with no success !!!
> 
> However, 12.13 in 4 bytes, whilst working like a charm
>  with Linux, does NOT work 
> with OSX.
> 
> Would you know the format used by OSX?
> 
> Thanks.
> 
> Alex
>

Hi Daniel et al,

This is an excerpt from:
http://www.opensource.apple.com/source/AppleUSBAudio/AppleUSBAudio-
273.4.1/AppleUSBAudioStream.cpp

==============================================================
	associatedEndpoint.type = kUSBIsoc;
	associatedEndpoint.direction = kUSBIn;
	// The associated endpoint always goes "in"
	// The sample rate should be either
 a 3-byte 10.14 or a 4-byte 16.16
	associatedEndpoint.maxPacketSize = mFeedbackPacketSize;
	associatedEndpoint.interval = 0xFF;
	mAssociatedPipe = mStreamInterface->FindNextPipe (NULL, 
&associatedEndpoint);
	FailWithAction (NULL == mAssociatedPipe, result = 
kIOReturnError, Exit);
===============================================================

Alex