From 39c3314d0064f89147f21291ed1068cf83b18977 Mon Sep 17 00:00:00 2001
From: Chris Robinson <chris.kcat@gmail.com>
Date: Sun, 23 Sep 2018 22:59:16 -0700
Subject: Only compare the reverb params that induce a need for fading

The offsets and coefficients are controlled by a relatively small set of input
parameters, just with different base constants or different calculations. This
lead to numerous redundant checks since if one value didn't change, others that
use the same inputs wouldn't have either.
---
 Alc/effects/reverb.c | 64 +++++++++++++++++++++++++++++++++-------------------
 1 file changed, 41 insertions(+), 23 deletions(-)

diff --git a/Alc/effects/reverb.c b/Alc/effects/reverb.c
index 9e8b8dd4..cfce5623 100644
--- a/Alc/effects/reverb.c
+++ b/Alc/effects/reverb.c
@@ -283,6 +283,15 @@ typedef struct ReverbState {
     ALfloat *SampleBuffer;
     ALuint   TotalSamples;
 
+    struct {
+        /* Calculated parameters which indicate if cross-fading is needed after
+         * an update.
+         */
+        ALfloat Density, Diffusion;
+        ALfloat DecayTime, HFDecayTime, LFDecayTime;
+        ALfloat HFReference, LFReference;
+    } Params;
+
     /* Master effect filters */
     struct {
         BiquadFilter Lp;
@@ -340,6 +349,14 @@ static void ReverbState_Construct(ReverbState *state)
     state->TotalSamples = 0;
     state->SampleBuffer = NULL;
 
+    state->Params.Density = AL_EAXREVERB_DEFAULT_DENSITY;
+    state->Params.Diffusion = AL_EAXREVERB_DEFAULT_DIFFUSION;
+    state->Params.DecayTime = AL_EAXREVERB_DEFAULT_DECAY_TIME;
+    state->Params.HFDecayTime = AL_EAXREVERB_DEFAULT_DECAY_TIME*AL_EAXREVERB_DEFAULT_DECAY_HFRATIO;
+    state->Params.LFDecayTime = AL_EAXREVERB_DEFAULT_DECAY_TIME*AL_EAXREVERB_DEFAULT_DECAY_LFRATIO;
+    state->Params.HFReference = AL_EAXREVERB_DEFAULT_HFREFERENCE;
+    state->Params.LFReference = AL_EAXREVERB_DEFAULT_LFREFERENCE;
+
     for(i = 0;i < NUM_LINES;i++)
     {
         BiquadFilter_clear(&state->Filter[i].Lp);
@@ -929,7 +946,7 @@ static ALvoid Update3DPanning(const ALCdevice *Device, const ALfloat *Reflection
 #undef MATRIX_MULT
 }
 
-static ALvoid ReverbState_update(ReverbState *State, const ALCcontext *Context, const ALeffectslot *Slot, const ALeffectProps *props)
+static void ReverbState_update(ReverbState *State, const ALCcontext *Context, const ALeffectslot *Slot, const ALeffectProps *props)
 {
     const ALCdevice *Device = Context->Device;
     const ALlistener *Listener = Context->Listener;
@@ -1001,30 +1018,31 @@ static ALvoid ReverbState_update(ReverbState *State, const ALCcontext *Context,
         mini(State->Early.Offset[0][1], State->Late.Offset[0][1])
     );
 
-    /* Determine if delay-line cross-fading is required. TODO: Add some fuzz
-     * for the float comparisons? The math should be stable enough that the
-     * result should be the same if nothing's changed, and changes in the float
-     * values should (though may not always) be matched by changes in delay
-     * offsets.
+    /* Determine if delay-line cross-fading is required. Density is essentially
+     * a master control for the feedback delays, so changes the offsets of many
+     * delay lines.
      */
-    if(State->Late.DensityGain[1] != State->Late.DensityGain[0])
+    if(State->Params.Density != props->Reverb.Density ||
+        /* Diffusion and decay times influences the decay rate (gain) of the
+         * late reverb T60 filter.
+         */
+       State->Params.Diffusion != props->Reverb.Diffusion ||
+       State->Params.DecayTime != props->Reverb.DecayTime ||
+       State->Params.HFDecayTime != hfDecayTime ||
+       State->Params.LFDecayTime != lfDecayTime ||
+       /* HF/LF References control the weighting used to calculate the density
+        * gain.
+        */
+       State->Params.HFReference != props->Reverb.HFReference ||
+       State->Params.LFReference != props->Reverb.LFReference)
         State->FadeCount = 0;
-    else for(i = 0;i < NUM_LINES;i++)
-    {
-        if(State->EarlyDelayTap[i][1] != State->EarlyDelayTap[i][0] ||
-           State->EarlyDelayCoeff[i][1] != State->EarlyDelayCoeff[i][0] ||
-           State->Early.VecAp.Offset[i][1] != State->Early.VecAp.Offset[i][0] ||
-           State->Early.Offset[i][1] != State->Early.Offset[i][0] ||
-           State->Early.Coeff[i][1] != State->Early.Coeff[i][0] ||
-           State->LateDelayTap[i][1] != State->LateDelayTap[i][0] ||
-           State->Late.VecAp.Offset[i][1] != State->Late.VecAp.Offset[i][0] ||
-           State->Late.Offset[i][1] != State->Late.Offset[i][0] ||
-           State->Late.T60[i].MidGain[1] != State->Late.T60[i].MidGain[0])
-        {
-            State->FadeCount = 0;
-            break;
-        }
-    }
+    State->Params.Density = props->Reverb.Density;
+    State->Params.Diffusion = props->Reverb.Diffusion;
+    State->Params.DecayTime = props->Reverb.DecayTime;
+    State->Params.HFDecayTime = hfDecayTime;
+    State->Params.LFDecayTime = lfDecayTime;
+    State->Params.HFReference = props->Reverb.HFReference;
+    State->Params.LFReference = props->Reverb.LFReference;
 }
 
 
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