Merge pull request #10831 from kencooke/audio-hrtf-optimize

More HRTF optimizations

assignment-client/src/audio/AudioMixerSlave.cpp

@@ -497,13 +497,14 @@ float computeGain(const AvatarAudioStream& listeningNodeStream, const Positional
     // avatar: apply fixed off-axis attenuation to make them quieter as they turn away
     } else if (!isEcho && (streamToAdd.getType() == PositionalAudioStream::Microphone)) {
         glm::vec3 rotatedListenerPosition = glm::inverse(streamToAdd.getOrientation()) * relativePosition;
-        float angleOfDelivery = glm::angle(glm::vec3(0.0f, 0.0f, -1.0f),
-                                           glm::normalize(rotatedListenerPosition));
+
+        // source directivity is based on angle of emission, in local coordinates
+        glm::vec3 direction = glm::normalize(rotatedListenerPosition);
+        float angleOfDelivery = fastAcosf(glm::clamp(-direction.z, -1.0f, 1.0f));   // UNIT_NEG_Z is "forward"
 
         const float MAX_OFF_AXIS_ATTENUATION = 0.2f;
         const float OFF_AXIS_ATTENUATION_STEP = (1 - MAX_OFF_AXIS_ATTENUATION) / 2.0f;
-        float offAxisCoefficient = MAX_OFF_AXIS_ATTENUATION +
-            (angleOfDelivery * (OFF_AXIS_ATTENUATION_STEP / PI_OVER_TWO));
+        float offAxisCoefficient = MAX_OFF_AXIS_ATTENUATION + (angleOfDelivery * (OFF_AXIS_ATTENUATION_STEP / PI_OVER_TWO));
 
         gain *= offAxisCoefficient;
     }
@@ -545,7 +546,6 @@ float computeAzimuth(const AvatarAudioStream& listeningNodeStream, const Positio
         const glm::vec3& relativePosition) {
     glm::quat inverseOrientation = glm::inverse(listeningNodeStream.getOrientation());
 
-    //  Compute sample delay for the two ears to create phase panning
     glm::vec3 rotatedSourcePosition = inverseOrientation * relativePosition;
 
     // project the rotated source position vector onto the XZ plane
@@ -553,11 +553,16 @@ float computeAzimuth(const AvatarAudioStream& listeningNodeStream, const Positio
 
     const float SOURCE_DISTANCE_THRESHOLD = 1e-30f;
 
-    if (glm::length2(rotatedSourcePosition) > SOURCE_DISTANCE_THRESHOLD) {
+    float rotatedSourcePositionLength2 = glm::length2(rotatedSourcePosition);
+    if (rotatedSourcePositionLength2 > SOURCE_DISTANCE_THRESHOLD) {
+        
         // produce an oriented angle about the y-axis
-        return glm::orientedAngle(glm::vec3(0.0f, 0.0f, -1.0f), glm::normalize(rotatedSourcePosition), glm::vec3(0.0f, -1.0f, 0.0f));
-    } else {
-        // there is no distance between listener and source - return no azimuth
-        return 0;
+        glm::vec3 direction = rotatedSourcePosition * (1.0f / fastSqrtf(rotatedSourcePositionLength2));
+		float angle = fastAcosf(glm::clamp(-direction.z, -1.0f, 1.0f)); // UNIT_NEG_Z is "forward"
+        return (direction.x < 0.0f) ? -angle : angle;
+
+    } else {   
+        // no azimuth if they are in same spot
+        return 0.0f; 
     }
 }

libraries/audio-client/src/AudioClient.cpp

@@ -48,6 +48,7 @@
 
 #include "AudioClientLogging.h"
 #include "AudioLogging.h"
+#include "AudioHelpers.h"
 
 #include "AudioClient.h"
 
@@ -1688,23 +1689,24 @@ int AudioClient::calculateNumberOfFrameSamples(int numBytes) const {
 }
 
 float AudioClient::azimuthForSource(const glm::vec3& relativePosition) {
-    // copied from AudioMixer, more or less
     glm::quat inverseOrientation = glm::inverse(_orientationGetter());
     
-    // compute sample delay for the 2 ears to create phase panning
     glm::vec3 rotatedSourcePosition = inverseOrientation * relativePosition;
     
-    // project the rotated source position vector onto x-y plane
+    // project the rotated source position vector onto the XZ plane
     rotatedSourcePosition.y = 0.0f;
 
     static const float SOURCE_DISTANCE_THRESHOLD = 1e-30f;
 
-    if (glm::length2(rotatedSourcePosition) > SOURCE_DISTANCE_THRESHOLD) {
+    float rotatedSourcePositionLength2 = glm::length2(rotatedSourcePosition);
+    if (rotatedSourcePositionLength2 > SOURCE_DISTANCE_THRESHOLD) {
         
         // produce an oriented angle about the y-axis
-        return glm::orientedAngle(glm::vec3(0.0f, 0.0f, -1.0f), glm::normalize(rotatedSourcePosition), glm::vec3(0.0f, -1.0f, 0.0f));
-    } else {
-        
+        glm::vec3 direction = rotatedSourcePosition * (1.0f / fastSqrtf(rotatedSourcePositionLength2));
+		float angle = fastAcosf(glm::clamp(-direction.z, -1.0f, 1.0f)); // UNIT_NEG_Z is "forward"
+        return (direction.x < 0.0f) ? -angle : angle;
+
+    } else {   
         // no azimuth if they are in same spot
         return 0.0f; 
     }

libraries/shared/src/AudioHelpers.h

@@ -14,6 +14,8 @@
 
 #include <stdint.h>
 
+#include <NumericalConstants.h>
+
 const int IEEE754_MANT_BITS = 23;
 const int IEEE754_EXPN_BIAS = 127;
 
@@ -66,6 +68,48 @@ static inline float fastExp2f(float x) {
     return x * xi.f;
 }
 
+//
+// on x86 architecture, assume that SSE2 is present
+//
+#if defined(_M_IX86) || defined(_M_X64) || defined(__i386__) || defined(__x86_64__)
+
+#include <xmmintrin.h>
+// inline sqrtss, without requiring /fp:fast
+static inline float fastSqrtf(float x) {   
+    return _mm_cvtss_f32(_mm_sqrt_ss(_mm_set_ss(x)));
+}
+
+#else 
+
+static inline float fastSqrtf(float x) {   
+    return sqrtf(x);
+}
+
+#endif
+
+//
+// for -1 <= x <= 1, returns acos(x)
+// otherwise, returns NaN
+//
+// abs |error| < 7e-5, smooth
+//
+static inline float fastAcosf(float x) {
+
+    union { float f; int32_t i; } xi = { x };
+
+    int32_t sign = xi.i & 0x80000000;
+    xi.i ^= sign;   // fabs(x)
+
+    // compute sqrt(1-x) in parallel
+    float r = fastSqrtf(1.0f - xi.f);
+
+    // polynomial for acos(x)/sqrt(1-x) over x=[0,1]
+    xi.f = ((-0.0198439236f * xi.f + 0.0762021306f) * xi.f + -0.212940971f) * xi.f + 1.57079633f;
+
+    xi.f *= r;
+    return (sign ? PI - xi.f : xi.f);
+}
+
 //
 // Quantize a non-negative gain value to the nearest 0.5dB, and pack to a byte.
 //