[wdmaudiodev] Re: USB Audio/WASAPI channel limits?

  • From: Matthew van Eerde <Matthew.van.Eerde@xxxxxxxxxxxxx>
  • To: "wdmaudiodev@xxxxxxxxxxxxx" <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Wed, 5 Feb 2014 18:35:49 +0000

The "channel mask" section of a WAVEFORMATEXTENSIBLE is a 32-bit number. 
Perhaps you're tripping some wave format validation that assumes a valid 
WAVEFORMATEX only ever has fewer than 32 channels. (This sounds like a bug to 
me, since a channel mask of zero is always valid.)

From: wdmaudiodev-bounce@xxxxxxxxxxxxx 
[mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Jerry Evans
Sent: Wednesday, February 5, 2014 10:27 AM
To: wdmaudiodev@xxxxxxxxxxxxx
Subject: [wdmaudiodev] USB Audio/WASAPI channel limits?


I'm developing a USB2 input only audio device that exposes a large (N >= 24) 
number of channels.

The device is recognized and streams correctly on W7x64 at up to 32 channels, 
48K sample rate and both 16 and 24 bit sample sizes. Data is recorded 
accurately using various commercial WASAPI hosts (Sonar/Tracktion)

Windows, however, appears to baulk at any larger channel count. The various USB 
tracers (both stack and wire) show Windows sending a QUERY_CAPABILITIES every 
second or so when device is configured with 32 channels. Anything above that 
and zero action.

Is there some hard limit or have I missed something?



Other related posts: