[wdmaudiodev] Re: USB audio record problem

  • From: "Daniel E. Germann" <deg@xxxxxxxx>
  • To: <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Fri, 14 Oct 2011 19:55:22 -0500

Hi, Matthew.

Interesting.  So you're saying that KMixer won't do an automatic bit depth conversion in that case?  It certainly seems to be doing bit depth conversion for 16-bit-in-16-bit-container mode.  But it won't do it for 24-bit-in-32-bit-container mode?  So if I change the USB format descriptor to 24-bit-in-32-bit-container mode (and make the corresponding alignment changes to the data), then all will be well?  I hate to do that because it wastes a lot of USB bandwidth.

And that still doesn't explain why when I open the device in 24-bit-in-24-bit-container mode, it doesn't work.  That is the one format that ought to work -- it's exactly what the device supports.  But all I get in that mode are 000000's and FFFFFF's.  The only format I can get to work is 16-bit-in-16-bit-container.  Do you have any idea why this doesn't work?

Can any other USB audio device developers shed some light here?  Are you all using 24-bit-in-32-bit-container mode for your audio?  Is anyone successfully using 24-bit-in-24-bit-container mode?

Thank you,


From: Matthew van Eerde
To: <wdmaudiodev@xxxxxxxxxxxxx>
Date: Sat, 15 Oct 2011 00:26:42 +0000

If the device supports only 24-bits-in-24-bit containers, I would expect the
driver to fail any request for 24-bit-in-32-bit containers.  If the driver is
falsely accepting requests for formats that the hardware doesn't support, that
would explain why the audio data is corrupted.
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