Add an option to scale the output mix

Alc/ALu.c

@@ -234,7 +234,6 @@ ALvoid aluInitPanning(ALCdevice *Device)
     Channel Speaker2Chan[OUTPUTCHANNELS];
     ALfloat Alpha, Theta;
     ALint pos, offset;
-    ALfloat maxout;
     ALuint s, s2;
 
     for(s = 0;s < OUTPUTCHANNELS;s++)
@@ -381,23 +380,25 @@ ALvoid aluInitPanning(ALCdevice *Device)
             assert(0);
     }
 
-    maxout = 1.0f;
-    for(s = 0;s < OUTPUTCHANNELS;s++)
+    if(GetConfigValueBool(NULL, "scalemix", 0))
     {
-        ALfloat out = 0.0f;
-        for(s2 = 0;s2 < OUTPUTCHANNELS;s2++)
-            out += Device->ChannelMatrix[s2][s];
-        maxout = __max(maxout, out);
-    }
+        ALfloat maxout = 1.0f;
+        for(s = 0;s < OUTPUTCHANNELS;s++)
+        {
+            ALfloat out = 0.0f;
+            for(s2 = 0;s2 < OUTPUTCHANNELS;s2++)
+                out += Device->ChannelMatrix[s2][s];
+            maxout = __max(maxout, out);
+        }
 
-    maxout = 1.0f/maxout;
-    for(s = 0;s < OUTPUTCHANNELS;s++)
-    {
-        for(s2 = 0;s2 < OUTPUTCHANNELS;s2++)
-            Device->ChannelMatrix[s2][s] *= maxout;
+        maxout = 1.0f/maxout;
+        for(s = 0;s < OUTPUTCHANNELS;s++)
+        {
+            for(s2 = 0;s2 < OUTPUTCHANNELS;s2++)
+                Device->ChannelMatrix[s2][s] *= maxout;
+        }
     }
 
-
     for(pos = 0; pos < LUT_NUM; pos++)
     {
         /* clear all values */

alsoftrc.sample

@@ -102,6 +102,15 @@
 #  will cause stereo sounds to only play out the front speakers.
 #stereodup = false
 
+## scalemix:
+#  Sets whether to scale the remixed output. When the final mix is written to
+#  the device, the multi-channel data is remixed so pure-virtual channels (eg.
+#  front-center on stereo output) are remixed and added to available channels
+#  (eg. front-left and front-right). Scaling helps ensure that no single source
+#  will put out more than 100% on a given physical channel. This can cause a
+#  noticeable reduction in overall volume, however, so it is off by default.
+#scalemix = false
+
 ## drivers:
 #  Sets the backend driver list order, comma-seperated. Unknown backends and
 #  duplicated names are ignored. Unlisted backends won't be considered for use