From 181a4e9bdcd4598e8d10ffeb8df6c169d4ad0376 Mon Sep 17 00:00:00 2001
From: Ken Cooke <ken@highfidelity.io>
Date: Sun, 31 Mar 2019 11:32:29 -0700
Subject: [PATCH] Disable parameter interpolation from reset state Restores
 original behavior of constant-volume streams (no initial fade-in)

---
 libraries/audio/src/AudioFOA.cpp  |  9 ++++++++-
 libraries/audio/src/AudioFOA.h    |  2 ++
 libraries/audio/src/AudioHRTF.cpp | 21 +++++++++++++++++++++
 3 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/libraries/audio/src/AudioFOA.cpp b/libraries/audio/src/AudioFOA.cpp
index ddcdf7f250..0dd61fbd02 100644
--- a/libraries/audio/src/AudioFOA.cpp
+++ b/libraries/audio/src/AudioFOA.cpp
@@ -1081,10 +1081,15 @@ void AudioFOA::render(int16_t* input, float* output, int index, float qw, float
     // apply gain as uniform scale
     scaleMatrix_4x4(gain, rotation);
 
+    // disable interpolation from reset state
+    if (_resetState) {
+        memcpy(_rotationState, rotation, sizeof(_rotationState));
+    }
+
     // rotate and scale the soundfield
     rotate_4x4(in, _rotationState, rotation, crossfadeTable, FOA_BLOCK);
 
-    // rotation history update
+    // new parameters become old
     memcpy(_rotationState, rotation, sizeof(_rotationState));
 
     //
@@ -1119,4 +1124,6 @@ void AudioFOA::render(int16_t* input, float* output, int index, float qw, float
         output[2*i+0] += accBuffer[0][i + FOA_OVERLAP];
         output[2*i+1] += accBuffer[1][i + FOA_OVERLAP];
     }
+
+    _resetState = false;
 }
diff --git a/libraries/audio/src/AudioFOA.h b/libraries/audio/src/AudioFOA.h
index b8257e5190..e8cacc22ab 100644
--- a/libraries/audio/src/AudioFOA.h
+++ b/libraries/audio/src/AudioFOA.h
@@ -52,6 +52,8 @@ private:
 
     // orientation and gain history
     float _rotationState[4][4] = {};
+
+    bool _resetState = true;
 };
 
 #endif // AudioFOA_h
diff --git a/libraries/audio/src/AudioHRTF.cpp b/libraries/audio/src/AudioHRTF.cpp
index 6f7d01d3f9..e5e32781b0 100644
--- a/libraries/audio/src/AudioHRTF.cpp
+++ b/libraries/audio/src/AudioHRTF.cpp
@@ -1141,6 +1141,13 @@ void AudioHRTF::render(int16_t* input, float* output, int index, float azimuth,
     // apply global and local gain adjustment
     gain *= _gainAdjust;
 
+    // disable interpolation from reset state
+    if (_resetState) {
+        _azimuthState = azimuth;
+        _distanceState = distance;
+        _gainState = gain;
+    }
+
     // to avoid polluting the cache, old filters are recomputed instead of stored
     setFilters(firCoef, bqCoef, delay, index, _azimuthState, _distanceState, _gainState, L0);
 
@@ -1220,11 +1227,18 @@ void AudioHRTF::mixMono(int16_t* input, float* output, float gain, int numFrames
     // apply global and local gain adjustment
     gain *= _gainAdjust;
 
+    // disable interpolation from reset state
+    if (_resetState) {
+        _gainState = gain;
+    }
+
     // crossfade gain and accumulate
     gainfade_1x2(input, output, crossfadeTable, _gainState, gain, HRTF_BLOCK);
 
     // new parameters become old
     _gainState = gain;
+
+    _resetState = false;
 }
 
 void AudioHRTF::mixStereo(int16_t* input, float* output, float gain, int numFrames) {
@@ -1234,9 +1248,16 @@ void AudioHRTF::mixStereo(int16_t* input, float* output, float gain, int numFram
     // apply global and local gain adjustment
     gain *= _gainAdjust;
 
+    // disable interpolation from reset state
+    if (_resetState) {
+        _gainState = gain;
+    }
+
     // crossfade gain and accumulate
     gainfade_2x2(input, output, crossfadeTable, _gainState, gain, HRTF_BLOCK);
 
     // new parameters become old
     _gainState = gain;
+
+    _resetState = false;
 }