Unreal plugin 4.7.0, reverb crackles if output channel is not 2 #486
Description
System Information
Please provide the following information about your system:
-
Steam Audio version: 4.7.0
-
(If applicable) Unreal Engine version: 5.6
-
Operating System and version: Win11
-
(Optional) CPU architecture (e.g. x86-64, armv7): x86-64
Issue Description
If the output device in Windows is set to 4 channels, the reverb in Steam Audio produces a "hissing" sound. After comparing with the source code of Resonance Audio, I noticed that they handle the reverb submix based on the number of output channels.
void FResonanceAudioReverb::ProcessMixedAudio(const FSoundEffectSubmixInputData& InData, FSoundEffectSubmixOutputData& OutData)
{
// This is where we trigger Resonance Audio processing.
if (OutData.NumChannels == 2)
{
...
}
else if (OutData.NumChannels > 2)
{
...
}
else if (OutData.NumChannels == 1)
{
...
}
}
I imitated their logic and modified the plugin code for Steam Audio.
void FSteamAudioReverbSubmixPlugin::OnProcessAudio(const FSoundEffectSubmixInputData& InData, FSoundEffectSubmixOutputData& OutData)
{
...
if (bHasOutput && HRTF && AmbisonicsDecodeEffect && IndirectBuffer.data && OutBuffer.data)
{
...
// iplAudioBufferInterleave(Context, &OutBuffer, OutBufferData);
if (OutData.NumChannels == 1)
{
iplAudioBufferDownmix(Context, &OutBuffer, &MonoBuffer);
FMemory::Memcpy(MonoBuffer.data, OutBufferData, InData.NumFrames * sizeof(float));
}
else if (OutData.NumChannels == 2)
{
iplAudioBufferInterleave(Context, &OutBuffer, OutBufferData);
}
else
{
int32 output_offset = 0;
for (int32 i = 0; i < InData.NumFrames; ++i)
{
OutBufferData[output_offset] = OutBuffer.data[0][i];
OutBufferData[output_offset + 1] = OutBuffer.data[1][i];
output_offset += OutData.NumChannels;
}
}
}
}
}
After testing, the hissing sound disappeared, and there were no issues (I only tested with 4 channels).
This is probably a bug, right?
Steps To Reproduce
Steps to reproduce the behavior:
1.Click the bottom right corner of Windows 11.
2.On the right side of the volume slider, click "Select volume output."
3.Click "More volume settings."
4.Go to "Advanced" -> "More sound settings."
5.Click on the currently selected playback device.
6.Click "Configure" in the bottom left corner.
7.Select "Quadraphonic", and keep clicking "Next" to confirm.