From 224b9b8930014f503c5b0c29f5479c63206d32b8 Mon Sep 17 00:00:00 2001
From: Wojtek Figat <wojtek@figat.pl>
Date: Sun, 12 Dec 2021 12:51:08 +0100
Subject: [PATCH] Fix mono audio playback with XAudio2

---
 Source/Engine/Audio/XAudio2/AudioBackendXAudio2.cpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/Source/Engine/Audio/XAudio2/AudioBackendXAudio2.cpp b/Source/Engine/Audio/XAudio2/AudioBackendXAudio2.cpp
index edced31a1..c16415976 100644
--- a/Source/Engine/Audio/XAudio2/AudioBackendXAudio2.cpp
+++ b/Source/Engine/Audio/XAudio2/AudioBackendXAudio2.cpp
@@ -817,7 +817,14 @@ void AudioBackendXAudio2::Base_Update()
             dsp.DopplerFactor = 1.0f;
             Platform::MemoryClear(dsp.pMatrixCoefficients, sizeof(XAudio2::MatrixCoefficients));
             dsp.pMatrixCoefficients[0] = 1.0f;
-            dsp.pMatrixCoefficients[3] = 1.0f;
+            if (source.Format.nChannels == 1)
+            {
+                dsp.pMatrixCoefficients[1] = 1.0f;
+            }
+            else
+            {
+                dsp.pMatrixCoefficients[3] = 1.0f;
+            }
         }
 
         const float frequencyRatio = dopplerFactor * source.Pitch * dsp.DopplerFactor;