Don't use custom decoder configurations with mono or stereo

By default, stereo outputs using UHJ, which renders to a B-Format buffer that
gets run through a UHJ encoder for output. It may also output using pair-wise
panning, which pans between -30 and +30 degrees with the speakers at the two
ends. In both cases, the stereo coefficients are ignored.

Mono, having only one output channel, can realistically only attenuate its
channel. Turning the volume up and down accomplishes the same result.

1 files changed, 13 insertions, 0 deletions

diff --git a/Alc/panning.c b/Alc/panning.c
index 90122550..c3145cd7 100644
--- a/Alc/panning.c
+++ b/Alc/panning.c
@@ -390,6 +390,13 @@ static bool LoadChannelSetup(ALCdevice *device)
     AmbDecConf conf;
     ALuint i, j;
 
+    /* Don't use custom decoders with mono or stereo output (stereo is using
+     * UHJ or pair-wise panning, thus ignores the custom coefficients anyway,
+     * and mono would realistically only specify attenuation on the output).
+     */
+    if(device->FmtChans == DevFmtMono || device->FmtChans == DevFmtStereo)
+        return false;
+
     layout = GetChannelLayoutName(device->FmtChans);
     if(!layout) return false;
 
@@ -629,6 +636,12 @@ ALvoid aluInitPanning(ALCdevice *device)
 
         ambdec_init(&conf);
 
+        /* Don't do HQ ambisonic decoding with mono or stereo output. Same
+         * reasons as in LoadChannelSetup.
+         */
+        if(device->FmtChans == DevFmtMono || device->FmtChans == DevFmtStereo)
+            goto ambi_fail;
+
         layout = GetChannelLayoutName(device->FmtChans);
         if(!layout) goto ambi_fail;