[wdmaudiodev] Re: USB audio record problem

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,
-Dan

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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.