Disable parameter interpolation from reset state

Restores original behavior of constant-volume streams (no initial fade-in)

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;
 }

libraries/audio/src/AudioFOA.h

@@ -52,6 +52,8 @@ private:
 
     // orientation and gain history
     float _rotationState[4][4] = {};
+
+    bool _resetState = true;
 };
 
 #endif // AudioFOA_h

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;
 }