Use a macro to specify the ambisonic periphonic channel mask

Alc/bformatdec.c

@@ -310,7 +310,7 @@ void bformatdec_reset(BFormatDec *dec, const AmbDecConf *conf, ALuint chancount,
     ratio = 400.0f / (ALfloat)srate;
     for(i = 0;i < 4;i++)
         bandsplit_init(&dec->UpSampler.XOver[i], ratio);
-    if((conf->ChanMask & ~0x831b))
+    if((conf->ChanMask&AMBI_PERIPHONIC_MASK))
     {
         dec->UpSampler.MatrixHF = CubeMatrixHF;
         dec->UpSampler.MatrixLF = CubeMatrixLF;

Alc/panning.c

@@ -673,7 +673,7 @@ static void InitHQPanning(ALCdevice *device, const AmbDecConf *conf, const ALuin
     if(GetConfigValueBool(devname, "decoder", "distance-comp", 1))
         decflags |= BFDF_DistanceComp;
 
-    if((conf->ChanMask & ~0x831b))
+    if((conf->ChanMask&AMBI_PERIPHONIC_MASK))
     {
         count = (conf->ChanMask > 0x1ff) ? 16 :
                 (conf->ChanMask > 0xf) ? 9 : 4;
@@ -701,7 +701,7 @@ static void InitHQPanning(ALCdevice *device, const AmbDecConf *conf, const ALuin
     TRACE("Enabling %s-band %s-order%s ambisonic decoder\n",
         (conf->FreqBands == 1) ? "single" : "dual",
         (conf->ChanMask > 0xf) ? (conf->ChanMask > 0x1ff) ? "third" : "second" : "first",
-        (conf->ChanMask & ~0x831b) ? " periphonic" : ""
+        (conf->ChanMask&AMBI_PERIPHONIC_MASK) ? " periphonic" : ""
     );
     bformatdec_reset(device->AmbiDecoder, conf, count, device->Frequency,
                      speakermap, decflags);

OpenAL32/Include/alMain.h

@@ -483,10 +483,19 @@ enum RenderMode {
 
 /* The maximum number of Ambisonics coefficients. For a given order (o), the
  * size needed will be (o+1)**2, thus zero-order has 1, first-order has 4,
- * second-order has 9, and third-order has 16. */
+ * second-order has 9, third-order has 16, and fourth-order has 25. */
 #define MAX_AMBI_ORDER  3
 #define MAX_AMBI_COEFFS ((MAX_AMBI_ORDER+1) * (MAX_AMBI_ORDER+1))
 
+/* A bitmask of ambisonic channels with height information. If none of these
+ * channels are used/needed, there's no height (e.g. with most surround sound
+ * speaker setups). This only specifies up to 4th order, which is the highest
+ * order a 32-bit mask value can specify (a 64-bit mask could handle up to 7th
+ * order). This is ACN ordering, with bit 0 being ACN 0, etc.
+ */
+#define AMBI_PERIPHONIC_MASK (0xfe7ce4)
+
+
 typedef ALfloat ChannelConfig[MAX_AMBI_COEFFS];
 typedef struct BFChannelConfig {
     ALfloat Scale;