Fix 5.1 surround sound

Apparently, 5.1 surround sound is supposed to use the "side" channels, not the
back channels, and we've been wrong this whole time. That means the "5.1 Side"
is actually the correct 5.1 setup, and using the back channels is anomalous.

Additionally, this means the 5.1 buffer format should also use the the side
channels instead of the back channels.

A final note: the 5.1 mixing coefficients are changed so both use the original
5.1 surround sound set (with the surround channels at +/-110 degrees). So the
only difference now between 5.1 "side" and 5.1 "back" is the channel labels.

1 files changed, 2 insertions, 2 deletions

diff --git a/Alc/ALu.c b/Alc/ALu.c
index cf8bfcfb..009d5366 100644
--- a/Alc/ALu.c
+++ b/Alc/ALu.c
@@ -257,8 +257,8 @@ ALvoid CalcNonAttnSourceParams(ALvoice *voice, const ALsource *ALSource, const A
         { FrontRight,  DEG2RAD(  30.0f), DEG2RAD(0.0f) },
         { FrontCenter, DEG2RAD(   0.0f), DEG2RAD(0.0f) },
         { LFE, 0.0f, 0.0f },
-        { BackLeft,    DEG2RAD(-110.0f), DEG2RAD(0.0f) },
-        { BackRight,   DEG2RAD( 110.0f), DEG2RAD(0.0f) }
+        { SideLeft,    DEG2RAD(-110.0f), DEG2RAD(0.0f) },
+        { SideRight,   DEG2RAD( 110.0f), DEG2RAD(0.0f) }
     };
     static const struct ChanMap X61Map[7] = {
         { FrontLeft,    DEG2RAD(-30.0f), DEG2RAD(0.0f) },