From fc9cb2fbd8b96fd4bddf3123b5c5479bec089d7f Mon Sep 17 00:00:00 2001
From: Chris Robinson <chris.kcat@gmail.com>
Date: Thu, 21 Sep 2017 10:20:59 -0700
Subject: [PATCH] Use the app-specified speed of sound for reverb decay

Specifically, the initial reverb decay as determined by the source distance,
and the reverb decayhf limit from air absorption.
---
 Alc/ALu.c            |  3 ++-
 Alc/effects/reverb.c | 11 +++++++----
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/Alc/ALu.c b/Alc/ALu.c
index dc14815d..dcd00c5b 100644
--- a/Alc/ALu.c
+++ b/Alc/ALu.c
@@ -1105,7 +1105,8 @@ static void CalcAttnSourceParams(ALvoice *voice, const struct ALvoiceProps *prop
         else if(SendSlots[i]->Params.AuxSendAuto)
         {
             RoomRolloff[i] = SendSlots[i]->Params.RoomRolloff + props->RoomRolloffFactor;
-            DecayDistance[i] = SendSlots[i]->Params.DecayTime * SPEEDOFSOUNDMETRESPERSEC;
+            DecayDistance[i] = SendSlots[i]->Params.DecayTime * Listener->Params.SpeedOfSound *
+                               Listener->Params.MetersPerUnit;
             DecayHFDistance[i] = DecayDistance[i] * SendSlots[i]->Params.DecayHFRatio;
             if(SendSlots[i]->Params.DecayHFLimit)
             {
diff --git a/Alc/effects/reverb.c b/Alc/effects/reverb.c
index 75790eae..455a433a 100644
--- a/Alc/effects/reverb.c
+++ b/Alc/effects/reverb.c
@@ -29,6 +29,7 @@
 #include "alAuxEffectSlot.h"
 #include "alEffect.h"
 #include "alFilter.h"
+#include "alListener.h"
 #include "alError.h"
 #include "mixer_defs.h"
 
@@ -694,7 +695,7 @@ static inline ALvoid CalcMatrixCoeffs(const ALfloat diffusion, ALfloat *x, ALflo
  * filters.
  */
 static ALfloat CalcLimitedHfRatio(const ALfloat hfRatio, const ALfloat airAbsorptionGainHF,
-                                  const ALfloat decayTime)
+                                  const ALfloat decayTime, const ALfloat SpeedOfSound)
 {
     ALfloat limitRatio;
 
@@ -703,8 +704,8 @@ static ALfloat CalcLimitedHfRatio(const ALfloat hfRatio, const ALfloat airAbsorp
      * equation, solve for HF ratio.  The delay length is cancelled out of
      * the equation, so it can be calculated once for all lines.
      */
-    limitRatio = 1.0f / (CalcDecayLength(airAbsorptionGainHF, decayTime) *
-                         SPEEDOFSOUNDMETRESPERSEC);
+    limitRatio = 1.0f / (CalcDecayLength(airAbsorptionGainHF, decayTime) * SpeedOfSound);
+
     /* Using the limit calculated above, apply the upper bound to the HF
      * ratio. Also need to limit the result to a minimum of 0.1, just like
      * the HF ratio parameter.
@@ -1310,6 +1311,7 @@ static ALvoid Update3DPanning(const ALCdevice *Device, const ALfloat *Reflection
 static ALvoid ALreverbState_update(ALreverbState *State, const ALCcontext *Context, const ALeffectslot *Slot, const ALeffectProps *props)
 {
     const ALCdevice *Device = Context->Device;
+    const ALlistener *Listener = Context->Listener;
     ALuint frequency = Device->Frequency;
     ALfloat lfScale, hfScale, hfRatio;
     ALfloat lfDecayTime, hfDecayTime;
@@ -1360,7 +1362,8 @@ static ALvoid ALreverbState_update(ALreverbState *State, const ALCcontext *Conte
     hfRatio = props->Reverb.DecayHFRatio;
     if(props->Reverb.DecayHFLimit && props->Reverb.AirAbsorptionGainHF < 1.0f)
         hfRatio = CalcLimitedHfRatio(hfRatio, props->Reverb.AirAbsorptionGainHF,
-                                     props->Reverb.DecayTime);
+                                     props->Reverb.DecayTime, Listener->Params.SpeedOfSound *
+                                     Listener->Params.MetersPerUnit);
 
     /* Calculate the LF/HF decay times. */
     lfDecayTime = clampf(props->Reverb.DecayTime * props->Reverb.DecayLFRatio,
-- 
2.11.4.GIT