From b4ffdfab81827626a3da2882218d401fd83cf375 Mon Sep 17 00:00:00 2001
From: Chris Robinson <chris.kcat@gmail.com>
Date: Wed, 6 Feb 2008 22:18:50 -0800
Subject: [PATCH] Add an option for duplicating stereo sources on the back
 speakers

---
 Alc/ALc.c              |  8 +++++++-
 Alc/ALu.c              | 23 +++++++++++++++++------
 OpenAL32/Include/alu.h |  2 ++
 alsoftrc.sample        |  8 ++++++++
 4 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/Alc/ALc.c b/Alc/ALc.c
index b485ec2e..a21b90db 100644
--- a/Alc/ALc.c
+++ b/Alc/ALc.c
@@ -201,7 +201,7 @@ static void InitAL(void)
     if(!done)
     {
         int i;
-        const char *devs;
+        const char *devs, *str;
 
         InitializeCriticalSection(&_alMutex);
         ALTHUNK_INIT();
@@ -250,6 +250,12 @@ static void InitAL(void)
         for(i = 0;BackendList[i].Init;i++)
             BackendList[i].Init(&BackendList[i].Funcs);
         done = 1;
+
+        str = GetConfigValue(NULL, "stereodup", "false");
+        DuplicateStereo = (strcasecmp(str, "true") == 0 ||
+                           strcasecmp(str, "yes") == 0 ||
+                           strcasecmp(str, "on") == 0 ||
+                           atoi(str) != 0);
     }
 }
 
diff --git a/Alc/ALu.c b/Alc/ALu.c
index 79603425..756dce20 100644
--- a/Alc/ALu.c
+++ b/Alc/ALu.c
@@ -82,6 +82,8 @@ enum {
     OUTPUTCHANNELS
 };
 
+ALboolean DuplicateStereo = AL_FALSE;
+
 /* NOTE: The AL_FORMAT_REAR* enums aren't handled here be cause they're
  *       converted to AL_FORMAT_QUAD* when loaded */
 __inline ALuint aluBytesFromFormat(ALenum format)
@@ -752,14 +754,15 @@ ALvoid aluMixData(ALCcontext *ALContext,ALvoid *buffer,ALsizei size,ALenum forma
                         }
                         else
                         {
+                            ALfloat samp1, samp2;
                             //First order interpolator (front left)
-                            value = (ALfloat)((ALshort)(((Data[k*Channels  ]*((1L<<FRACTIONBITS)-fraction))+(Data[(k+1)*Channels  ]*(fraction)))>>FRACTIONBITS));
-                            DryBuffer[j][FRONT_LEFT] += value*DrySend[FRONT_LEFT];
-                            WetBuffer[j][FRONT_LEFT] += value*WetSend[FRONT_LEFT];
+                            samp1 = (ALfloat)((ALshort)(((Data[k*Channels  ]*((1L<<FRACTIONBITS)-fraction))+(Data[(k+1)*Channels  ]*(fraction)))>>FRACTIONBITS));
+                            DryBuffer[j][FRONT_LEFT] += samp1*DrySend[FRONT_LEFT];
+                            WetBuffer[j][FRONT_LEFT] += samp1*WetSend[FRONT_LEFT];
                             //First order interpolator (front right)
-                            value = (ALfloat)((ALshort)(((Data[k*Channels+1]*((1L<<FRACTIONBITS)-fraction))+(Data[(k+1)*Channels+1]*(fraction)))>>FRACTIONBITS));
-                            DryBuffer[j][FRONT_RIGHT] += value*DrySend[FRONT_RIGHT];
-                            WetBuffer[j][FRONT_RIGHT] += value*WetSend[FRONT_RIGHT];
+                            samp2 = (ALfloat)((ALshort)(((Data[k*Channels+1]*((1L<<FRACTIONBITS)-fraction))+(Data[(k+1)*Channels+1]*(fraction)))>>FRACTIONBITS));
+                            DryBuffer[j][FRONT_RIGHT] += samp2*DrySend[FRONT_RIGHT];
+                            WetBuffer[j][FRONT_RIGHT] += samp2*WetSend[FRONT_RIGHT];
                             if(Channels >= 4)
                             {
                                 int i = 2;
@@ -803,6 +806,14 @@ ALvoid aluMixData(ALCcontext *ALContext,ALvoid *buffer,ALsizei size,ALenum forma
                                     i++;
                                 }
                             }
+                            else if(DuplicateStereo)
+                            {
+                                //Duplicate stereo channels on the back speakers
+                                DryBuffer[j][BACK_LEFT] += samp1*DrySend[BACK_LEFT];
+                                WetBuffer[j][BACK_LEFT] += samp1*WetSend[BACK_LEFT];
+                                DryBuffer[j][BACK_RIGHT] += samp2*DrySend[BACK_RIGHT];
+                                WetBuffer[j][BACK_RIGHT] += samp2*WetSend[BACK_RIGHT];
+                            }
                         }
                         DataPosFrac += increment;
                         j++;
diff --git a/OpenAL32/Include/alu.h b/OpenAL32/Include/alu.h
index d43e0127..6fab1fae 100644
--- a/OpenAL32/Include/alu.h
+++ b/OpenAL32/Include/alu.h
@@ -8,6 +8,8 @@
 extern "C" {
 #endif
 
+extern ALboolean DuplicateStereo;
+
 __inline ALuint aluBytesFromFormat(ALenum format);
 __inline ALuint aluChannelsFromFormat(ALenum format);
 ALvoid aluMixData(ALCcontext *context,ALvoid *buffer,ALsizei size,ALenum format);
diff --git a/alsoftrc.sample b/alsoftrc.sample
index c3bb9e83..8eaa0f4f 100644
--- a/alsoftrc.sample
+++ b/alsoftrc.sample
@@ -44,6 +44,14 @@ sources = 256  # Sets the maximum number of allocatable sources. Lower values
                # may help for systems with apps that try to play more sounds
                # than the CPU can handle. Default is 256
 
+stereodup =  # Sets whether to duplicate stereo sounds on the rear speakers for
+             # 4+ channel output. This can make stereo sources substantially
+             # louder than mono or even 4+ channel sources, but provides a
+             # "fuller" playback quality. True, yes, on, and non-0 values will
+             # duplicate stereo sources. 0 and anything else will cause stereo
+             # sounds to only play out the front speakers.
+             # Default is false
+
 drivers =  # Sets the backend driver list order, comma-seperated. Unknown
            # backends and duplicated names are ignored, and unlisted backends
            # won't be considered for use. An empty list means the default.
-- 
2.11.4.GIT