X3DAUDIO_CALCULATE_ZEROCENTER should be set for proper volume levels returned by X3DAudioCalculate

[HSNB]

It seems that even when there's no Front Center speaker according to the Mastering Voice Channel Mask (SPEAKER_FRONT_CENTER), X3DAudioCalculate will still calculate the matrix volume levels as if there is.

This causes the volume of the sound to play at a lower volume.

For example if you have a 2 channel output (headset), meaning Channel Mask is SPEAKER_FRONT_LEFT | SPEAKER_FRONT_RIGHT. It is still needed to set X3DAUDIO_CALCULATE_ZEROCENTER even though the comment of X3DAUDIO_CALCULATE_ZEROCENTER says "valid only for matrix calculations with final mix formats that have a front center channel".

I could be wrong in understanding 3D audio, but if I'm not setting this ZEROCENTER flag what happens is that even a 3D sound playing at a distance of 0 away from the listener, makes the sound play at a lower volume than the actual sound file, which seems like a wrong thing to me?

[HSNB]

Note that DirectSound also has this "bug", but in DirectSound there's no way to set a "Zero Center" flag to fix it.

[walbourn]

Interesting. Thanks for the feedback.

Looking at the source to XAudio3DCalculate, they clearly have validation that enforces the flag as documented:

if (u32Flags & X3DAUDIO_CALCULATE_ZEROCENTER) {
    if (!(u32Flags & X3DAUDIO_CALCULATE_MATRIX) || !(pHandle->u32SpeakerChannelMask & SPEAKER_FRONT_CENTER)) {
        X3DDEBUG_MESSAGE(X3DDEBUG_ERROR, "X3DAUDIO_CALCULATE_ZEROCENTER valid only for matrix calculations with final mix formats that have a front center channel");
        fValid = FALSE;
    }
}

So if there is no FRONT_CENTER in the provided channel mask or you don't have the flag to calculate a matrix set, the debugging logic would say it's not valid.

Furthermore, the actual implementation for X3DAUDIO_CALCULATE_ZEROCENTER uses this flag specifically for the following speaker configs to remove one speaker channel:

SPEAKER_SURROUND
SPEAKER_5POINT1
SPEAKER_7POINT1
SPEAKER_5POINT1_SURROUND
SPEAKER_7POINT1_SURROUND

The other logic for that flag only applies if there are more than 2 speaker channels (since the first two are always left/right and the third is the center).

In other words, I don't see where in the code that flag would impact a 2 channel speaker configuration.

[walbourn]

Note that with that said, perhaps I should offer a way to set that flag through DirectX Tool Kit for Audio for scenarios where it is desirable.

[HSNB]

In other words, I don't see where in the code that flag would impact a 2 channel speaker configuration.

If you have any project that you can test it with please do, it for sure matters.

mDSPSettings.SrcChannelCount = 1
mDSPSettings.DstChannelCount = 2

Without ZEROCENTER the matrix contains: 0.5 0.5
With ZEROCENTER the matrix contains: 1.0 1.0

XAudio 2.9 Redist on Windows 10.
Also happens in normal XAudio 2.9 (No Redist).