WASAPI speaker mask

#1

I’m noticing that with my Realtek 7.1 motherboard audio, I don’t seem to be able to send audio to the 7th and 8th channels in WASAPI shared mode.

I think this is due to the hardcoded speaker mask used in WASAPIDeviceBase::tryInitialisingWithFormat:

switch (numChannels) { // snip case 8: format.dwChannelMask = SPEAKER_FRONT_LEFT | SPEAKER_FRONT_RIGHT | SPEAKER_FRONT_CENTER | SPEAKER_LOW_FREQUENCY | SPEAKER_BACK_LEFT | SPEAKER_BACK_RIGHT | SPEAKER_FRONT_LEFT_OF_CENTER | SPEAKER_FRONT_RIGHT_OF_CENTER; break; default: break; }
This sets dwChannelMask to 0xff. However, the Realtek is using a channel mask of 0x63f for its mix format. If I change the channel mask in tryInitialisingWithFormat to 0x63f, I can play out the upper channels just fine.

I suggest that the JUCE channel mask be set to match the mix format.

Matt

#2

Ok… but down at line 582, it should use the suggested format if the one that’s being asked for fails… Isn’t that working?

#3

The problem is that the call to IsFormatSupported succeeds even if the speaker mask is different. I added some debug output to the WASAPI code:

WASAPIDeviceBase constructor
GetMixFormat dwChannelMask:63f

tryInitialisingWithFormat
Calling IsFormatSupported with dwChannelMask:ff
IsFormatSupported returned hr:0
nearestFormat:0

So IsFormatSupported is perfectly happy with the mis-matched channel mask and doesn’t provide a suggested format. Using the channel mask from the mix format works.

Matt

#4

Gotcha. Try it now…

#5

That works fine. Thanks, Jules.

Matt