From e73b198f9291437a9cac90b8b9e94363ebbabc52 Mon Sep 17 00:00:00 2001
From: Volker Fischer <corrados@users.noreply.github.com>
Date: Thu, 18 Jun 2020 19:16:31 +0200
Subject: [PATCH] the local pan middle position is no longer attenuated in
 Mono-in/Stereo-out mode (#353)

---
 ChangeLog      |  1 +
 src/client.cpp | 12 +++++++-----
 src/server.cpp |  4 ++--
 src/util.h     | 19 +++++++++++++------
 4 files changed, 23 insertions(+), 13 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index f453a3ff..38b29771 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -15,6 +15,7 @@
 
 - add a headless build type which does not depend on QtGui/QtWidgets, coded by marcan (#322)
 
+- the local pan middle position is no longer attenuated in Mono-in/Stereo-out mode (#353)
 
 
 
diff --git a/src/client.cpp b/src/client.cpp
index 35b8fea5..b88ace5a 100755
--- a/src/client.cpp
+++ b/src/client.cpp
@@ -991,8 +991,8 @@ void CClient::ProcessAudioDataIntern ( CVector<int16_t>& vecsStereoSndCrd )
         if ( eAudioChannelConf == CC_STEREO )
         {
             // for stereo only apply pan attenuation on one channel (same as pan in the server)
-            const double dGainL = std::min ( 0.5, 1 - dPan ) * 2;
-            const double dGainR = std::min ( 0.5, dPan ) * 2;
+            const double dGainL = MathUtils::GetLeftPan ( dPan, false );
+            const double dGainR = MathUtils::GetRightPan ( dPan, false );
 
             for ( i = 0, j = 0; i < iMonoBlockSizeSam; i++, j += 2 )
             {
@@ -1004,12 +1004,14 @@ void CClient::ProcessAudioDataIntern ( CVector<int16_t>& vecsStereoSndCrd )
         }
         else
         {
-            // for mono implement a cross-fade between channels and mix them
-            const double dGainL = 1 - dPan;
-            const double dGainR = dPan;
+            // for mono implement a cross-fade between channels and mix them, for
+            // mono-in/stereo-out use no attenuation in pan center
+            const double dGainL = MathUtils::GetLeftPan ( dPan, eAudioChannelConf != CC_MONO_IN_STEREO_OUT );
+            const double dGainR = MathUtils::GetRightPan ( dPan, eAudioChannelConf != CC_MONO_IN_STEREO_OUT );
 
             for ( i = 0, j = 0; i < iMonoBlockSizeSam; i++, j += 2 )
             {
+                // note that we need the Double2Short for stereo pan mode
                 vecsStereoSndCrd[i] = Double2Short (
                     dGainL * vecsStereoSndCrd[j] + dGainR * vecsStereoSndCrd[j + 1] );
             }
diff --git a/src/server.cpp b/src/server.cpp
index 8c449e8b..0f2aa184 100755
--- a/src/server.cpp
+++ b/src/server.cpp
@@ -1203,8 +1203,8 @@ void CServer::ProcessData ( const CVector<CVector<int16_t> >& vecvecsData,
 
             // calculate combined gain/pan for each stereo channel where we define
             // the panning that center equals full gain for both channels
-            const double dGainL = std::min ( 0.5, 1 - dPan ) * 2 * dGain;
-            const double dGainR = std::min ( 0.5, dPan ) * 2 * dGain;
+            const double dGainL = MathUtils::GetLeftPan ( dPan, false ) * dGain;
+            const double dGainR = MathUtils::GetRightPan ( dPan, false ) * dGain;
 
             // if channel gain is 1, avoid multiplication for speed optimization
             if ( ( dGainL == static_cast<double> ( 1.0 ) ) && ( dGainR == static_cast<double> ( 1.0 ) ) )
diff --git a/src/util.h b/src/util.h
index 9118f617..ee70d662 100755
--- a/src/util.h
+++ b/src/util.h
@@ -508,8 +508,6 @@ private:
 /******************************************************************************\
 * Other Classes/Enums                                                          *
 \******************************************************************************/
-
-
 // Audio channel configuration -------------------------------------------------
 enum EAudChanConf
 {
@@ -1199,13 +1197,11 @@ public:
         // different IIR weights for up and down direction
         if ( dNewValue < dOldValue )
         {
-            dOldValue =
-                dOldValue * dWeightDown + ( 1.0 - dWeightDown ) * dNewValue;
+            dOldValue = dOldValue * dWeightDown + ( 1.0 - dWeightDown ) * dNewValue;
         }
         else
         {
-            dOldValue =
-                dOldValue * dWeightUp + ( 1.0 - dWeightUp ) * dNewValue;
+            dOldValue = dOldValue * dWeightUp + ( 1.0 - dWeightUp ) * dNewValue;
         }
     }
 
@@ -1223,6 +1219,17 @@ public:
             return round ( dValue + dHysteresis );
         }
     }
+
+    // calculate pan gains: in cross fade mode the pan center is attenuated
+    // by 6 dB, otherwise the center equals full gain for both channels
+    static inline double GetLeftPan ( const double dPan, const bool bXFade)
+    {
+        return bXFade ? 1 - dPan : std::min ( 0.5, 1 - dPan ) * 2;
+    }
+    static inline double GetRightPan ( const double dPan, const bool bXFade)
+    {
+        return bXFade ? dPan : std::min ( 0.5, dPan ) * 2;
+    }
 };