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Merge pull request #12479 from kencooke/audio-nearfield-hrtf
Near-field HRTF
This commit is contained in:
Ken Cooke
GitHub
commit
328b5a1e8b
4 changed files with 260 additions and 62 deletions
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@ -49,7 +49,7 @@ void sendEnvironmentPacket(const SharedNodePointer& node, AudioMixerClientData&
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inline float approximateGain(const AvatarAudioStream& listeningNodeStream, const PositionalAudioStream& streamToAdd,
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const glm::vec3& relativePosition);
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inline float computeGain(const AudioMixerClientData& listenerNodeData, const AvatarAudioStream& listeningNodeStream,
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const PositionalAudioStream& streamToAdd, const glm::vec3& relativePosition, bool isEcho);
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const PositionalAudioStream& streamToAdd, const glm::vec3& relativePosition, float distance, bool isEcho);
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inline float computeAzimuth(const AvatarAudioStream& listeningNodeStream, const PositionalAudioStream& streamToAdd,
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const glm::vec3& relativePosition);
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@ -276,7 +276,7 @@ void AudioMixerSlave::addStream(AudioMixerClientData& listenerNodeData, const QU
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glm::vec3 relativePosition = streamToAdd.getPosition() - listeningNodeStream.getPosition();
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float distance = glm::max(glm::length(relativePosition), EPSILON);
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float gain = computeGain(listenerNodeData, listeningNodeStream, streamToAdd, relativePosition, isEcho);
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float gain = computeGain(listenerNodeData, listeningNodeStream, streamToAdd, relativePosition, distance, isEcho);
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float azimuth = isEcho ? 0.0f : computeAzimuth(listeningNodeStream, listeningNodeStream, relativePosition);
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const int HRTF_DATASET_INDEX = 1;
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@ -489,9 +489,6 @@ float approximateGain(const AvatarAudioStream& listeningNodeStream, const Positi
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// avatar: skip attenuation - it is too costly to approximate
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// distance attenuation: approximate, ignore zone-specific attenuations
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// this is a good approximation for streams further than ATTENUATION_START_DISTANCE
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// those streams closer will be amplified; amplifying close streams is acceptable
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// when throttling, as close streams are expected to be heard by a user
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float distance = glm::length(relativePosition);
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return gain / distance;
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@ -499,7 +496,7 @@ float approximateGain(const AvatarAudioStream& listeningNodeStream, const Positi
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}
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float computeGain(const AudioMixerClientData& listenerNodeData, const AvatarAudioStream& listeningNodeStream,
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const PositionalAudioStream& streamToAdd, const glm::vec3& relativePosition, bool isEcho) {
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const PositionalAudioStream& streamToAdd, const glm::vec3& relativePosition, float distance, bool isEcho) {
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float gain = 1.0f;
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// injector: apply attenuation
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@ -536,23 +533,13 @@ float computeGain(const AudioMixerClientData& listenerNodeData, const AvatarAudi
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break;
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}
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}
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// translate the zone setting to gain per log2(distance)
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float g = glm::clamp(1.0f - attenuationPerDoublingInDistance, EPSILON, 1.0f);
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// distance attenuation
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const float ATTENUATION_START_DISTANCE = 1.0f;
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float distance = glm::length(relativePosition);
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assert(ATTENUATION_START_DISTANCE > EPSILON);
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if (distance >= ATTENUATION_START_DISTANCE) {
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// translate the zone setting to gain per log2(distance)
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float g = 1.0f - attenuationPerDoublingInDistance;
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g = glm::clamp(g, EPSILON, 1.0f);
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// calculate the distance coefficient using the distance to this node
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float distanceCoefficient = fastExp2f(fastLog2f(g) * fastLog2f(distance/ATTENUATION_START_DISTANCE));
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// multiply the current attenuation coefficient by the distance coefficient
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gain *= distanceCoefficient;
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}
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// calculate the attenuation using the distance to this node
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// reference attenuation of 0dB at distance = 1.0m
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gain *= fastExp2f(fastLog2f(g) * fastLog2f(std::max(distance, HRTF_NEARFIELD_MIN)));
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gain = std::min(gain, 1.0f / HRTF_NEARFIELD_MIN);
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return gain;
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}
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@ -1824,16 +1824,9 @@ float AudioClient::azimuthForSource(const glm::vec3& relativePosition) {
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float AudioClient::gainForSource(float distance, float volume) {
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const float ATTENUATION_BEGINS_AT_DISTANCE = 1.0f;
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// I'm assuming that the AudioMixer's getting of the stream's attenuation
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// factor is basically same as getting volume
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float gain = volume;
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// attenuate based on distance
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if (distance >= ATTENUATION_BEGINS_AT_DISTANCE) {
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gain /= (distance/ATTENUATION_BEGINS_AT_DISTANCE); // attenuation = -6dB * log2(distance)
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}
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// attenuation = -6dB * log2(distance)
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// reference attenuation of 0dB at distance = 1.0m
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float gain = volume / std::max(distance, HRTF_NEARFIELD_MIN);
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return gain;
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}
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@ -71,6 +71,47 @@ ALIGN32 static const float crossfadeTable[HRTF_BLOCK] = {
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0.0029059408f, 0.0022253666f, 0.0016352853f, 0.0011358041f, 0.0007270137f, 0.0004089886f, 0.0001817865f, 0.0000454487f,
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};
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//
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// Fast approximation of the azimuth parallax correction,
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// for azimuth = [-pi,pi] and distance = [0.125,2].
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//
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// Correction becomes 0 at distance = 2.
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// Correction is continuous and smooth.
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//
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static const int NAZIMUTH = 8;
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static const float azimuthTable[NAZIMUTH][3] = {
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{ 0.018719007f, 0.097263971f, 0.080748954f }, // [-4pi/4,-3pi/4]
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{ 0.066995833f, 0.319754290f, 0.336963269f }, // [-3pi/4,-2pi/4]
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{ -0.066989851f, -0.101178847f, 0.006359474f }, // [-2pi/4,-1pi/4]
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{ -0.018727343f, -0.020357568f, 0.040065626f }, // [-1pi/4,-0pi/4]
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{ -0.005519051f, -0.018744412f, 0.040065629f }, // [ 0pi/4, 1pi/4]
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{ -0.001201296f, -0.025103593f, 0.042396711f }, // [ 1pi/4, 2pi/4]
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{ 0.001198959f, -0.032642381f, 0.048316220f }, // [ 2pi/4, 3pi/4]
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{ 0.005519640f, -0.053424870f, 0.073296888f }, // [ 3pi/4, 4pi/4]
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};
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//
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// Model the normalized near-field Distance Variation Filter.
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//
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// This version is parameterized by the DC gain correction, instead of directly by azimuth and distance.
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// A first-order shelving filter is used to minimize the disturbance in ITD.
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//
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// Loosely based on data from S. Spagnol, "Distance rendering and perception of nearby virtual sound sources
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// with a near-field filter model,” Applied Acoustics (2017)
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//
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static const int NNEARFIELD = 9;
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static const float nearFieldTable[NNEARFIELD][3] = { // { b0, b1, a1 }
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{ 0.008410604f, -0.000262748f, -0.991852144f }, // gain = 1/256
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{ 0.016758914f, -0.000529590f, -0.983770676f }, // gain = 1/128
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{ 0.033270607f, -0.001075350f, -0.967804743f }, // gain = 1/64
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{ 0.065567740f, -0.002213762f, -0.936646021f }, // gain = 1/32
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{ 0.127361554f, -0.004667324f, -0.877305769f }, // gain = 1/16
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{ 0.240536414f, -0.010201827f, -0.769665412f }, // gain = 1/8
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{ 0.430858205f, -0.023243052f, -0.592384847f }, // gain = 1/4
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{ 0.703238106f, -0.054157913f, -0.350919807f }, // gain = 1/2
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{ 1.000000000f, -0.123144711f, -0.123144711f }, // gain = 1/1
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};
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//
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// Model the frequency-dependent attenuation of sound propogation in air.
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//
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@ -168,6 +209,8 @@ static const float lowpassTable[NLOWPASS][5] = { // { b0, b1, b2, a1, a2 }
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{ 0.000076480f, 0.000024509f, -0.000000991f, -1.985807957f, 0.985907955f },
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};
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static const float HALFPI = 1.570796327f;
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static const float PI = 3.141592654f;
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static const float TWOPI = 6.283185307f;
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//
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@ -716,7 +759,7 @@ static void distanceBiquad(float distance, float& b0, float& b1, float& b2, floa
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//
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float x = distance;
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x = MIN(MAX(x, 1.0f), 1<<30);
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x = MIN(x, 1<<30);
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x *= x;
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x *= x; // x = distance^4
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@ -747,33 +790,181 @@ static void distanceBiquad(float distance, float& b0, float& b1, float& b2, floa
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a2 = lowpassTable[e+0][4] + frac * (lowpassTable[e+1][4] - lowpassTable[e+0][4]);
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}
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//
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// Geometric correction of the azimuth, to the angle at each ear.
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// D. Brungart, "Auditory parallax effects in the HRTF for nearby sources," IEEE WASPAA (1999).
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//
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static void nearFieldAzimuthCorrection(float azimuth, float distance, float& azimuthL, float& azimuthR) {
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#ifdef HRTF_AZIMUTH_EXACT
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float dx = distance * cosf(azimuth);
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float dy = distance * sinf(azimuth);
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float dx0 = HRTF_AZIMUTH_REF * cosf(azimuth);
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float dy0 = HRTF_AZIMUTH_REF * sinf(azimuth);
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azimuthL += atan2f(dy + HRTF_HEAD_RADIUS, dx) - atan2f(dy0 + HRTF_HEAD_RADIUS, dx0);
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azimuthR += atan2f(dy - HRTF_HEAD_RADIUS, dx) - atan2f(dy0 - HRTF_HEAD_RADIUS, dx0);
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#else
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// at reference distance, the azimuth parallax is correct
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float fy = (HRTF_AZIMUTH_REF - distance) / distance;
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float x0 = +azimuth;
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float x1 = -azimuth; // compute using symmetry
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const float RAD_TO_INDEX = 1.2732394f; // 8/(2*pi), rounded down
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int k0 = (int)(RAD_TO_INDEX * x0 + 4.0f);
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int k1 = (NAZIMUTH-1) - k0;
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assert(k0 >= 0);
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assert(k1 >= 0);
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assert(k0 < NAZIMUTH);
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assert(k1 < NAZIMUTH);
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// piecewise polynomial approximation over azimuth=[-pi,pi]
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float fx0 = (azimuthTable[k0][0] * x0 + azimuthTable[k0][1]) * x0 + azimuthTable[k0][2];
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float fx1 = (azimuthTable[k1][0] * x1 + azimuthTable[k1][1]) * x1 + azimuthTable[k1][2];
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// approximate the azimuth correction
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// NOTE: must converge to 0 when distance = HRTF_AZIMUTH_REF
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azimuthL += fx0 * fy;
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azimuthR -= fx1 * fy;
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#endif
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}
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//
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// Approximate the near-field DC gain correction at each ear.
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//
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static void nearFieldGainCorrection(float azimuth, float distance, float& gainL, float& gainR) {
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// normalized distance factor = [0,1] as distance = [HRTF_NEARFIELD_MAX,HRTF_HEAD_RADIUS]
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assert(distance < HRTF_NEARFIELD_MAX);
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assert(distance > HRTF_HEAD_RADIUS);
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float d = (HRTF_NEARFIELD_MAX - distance) * ( 1.0f / (HRTF_NEARFIELD_MAX - HRTF_HEAD_RADIUS));
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// angle of incidence at each ear
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float angleL = azimuth + HALFPI;
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float angleR = azimuth - HALFPI;
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if (angleL > +PI) {
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angleL -= TWOPI;
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}
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if (angleR < -PI) {
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angleR += TWOPI;
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}
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assert(angleL >= -PI);
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assert(angleL <= +PI);
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assert(angleR >= -PI);
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assert(angleR <= +PI);
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// normalized occlusion factor = [0,1] as angle of incidence = [0,pi]
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angleL *= angleL;
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angleR *= angleR;
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float cL = ((-0.000452339132f * angleL - 0.00173192444f) * angleL + 0.162476536f) * angleL;
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float cR = ((-0.000452339132f * angleR - 0.00173192444f) * angleR + 0.162476536f) * angleR;
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// approximate the gain correction
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// NOTE: must converge to 0 when distance = HRTF_NEARFIELD_MAX
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gainL -= d * cL;
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gainR -= d * cR;
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}
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//
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// Approximate the normalized near-field Distance Variation Function at each ear.
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// A. Kan, "Distance Variation Function for simulation of near-field virtual auditory space," IEEE ICASSP (2006)
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//
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static void nearFieldFilter(float gain, float& b0, float& b1, float& a1) {
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//
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// Computed from a lookup table quantized to gain = 2^(-N)
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// and reconstructed by piecewise linear interpolation.
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//
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// split gain into e and frac, such that gain = 2^(e+0) + frac * (2^(e+1) - 2^(e+0))
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int e;
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float frac;
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splitf(gain, e, frac);
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// clamp to table limits
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e += NNEARFIELD-1;
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if (e < 0) {
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e = 0;
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frac = 0.0f;
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}
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if (e > NNEARFIELD-2) {
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e = NNEARFIELD-2;
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frac = 1.0f;
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}
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assert(frac >= 0.0f);
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assert(frac <= 1.0f);
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assert(e+0 >= 0);
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assert(e+1 < NNEARFIELD);
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// piecewise linear interpolation
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b0 = nearFieldTable[e+0][0] + frac * (nearFieldTable[e+1][0] - nearFieldTable[e+0][0]);
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b1 = nearFieldTable[e+0][1] + frac * (nearFieldTable[e+1][1] - nearFieldTable[e+0][1]);
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a1 = nearFieldTable[e+0][2] + frac * (nearFieldTable[e+1][2] - nearFieldTable[e+0][2]);
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}
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static void azimuthToIndex(float azimuth, int& index0, int& index1, float& frac) {
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// convert from radians to table units
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azimuth *= (HRTF_AZIMUTHS / TWOPI);
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if (azimuth < 0.0f) {
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azimuth += HRTF_AZIMUTHS;
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}
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// table parameters
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index0 = (int)azimuth;
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index1 = index0 + 1;
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frac = azimuth - (float)index0;
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if (index1 >= HRTF_AZIMUTHS) {
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index1 -= HRTF_AZIMUTHS;
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}
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assert((index0 >= 0) && (index0 < HRTF_AZIMUTHS));
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assert((index1 >= 0) && (index1 < HRTF_AZIMUTHS));
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assert((frac >= 0.0f) && (frac < 1.0f));
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}
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// compute new filters for a given azimuth, distance and gain
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static void setFilters(float firCoef[4][HRTF_TAPS], float bqCoef[5][8], int delay[4],
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int index, float azimuth, float distance, float gain, int channel) {
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// convert from radians to table units
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azimuth *= HRTF_AZIMUTHS / TWOPI;
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// wrap to principle value
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while (azimuth < 0.0f) {
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azimuth += HRTF_AZIMUTHS;
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if (azimuth > PI) {
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azimuth -= TWOPI;
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}
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while (azimuth >= HRTF_AZIMUTHS) {
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azimuth -= HRTF_AZIMUTHS;
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assert(azimuth >= -PI);
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assert(azimuth <= +PI);
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distance = MAX(distance, HRTF_NEARFIELD_MIN);
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// compute the azimuth correction at each ear
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float azimuthL = azimuth;
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float azimuthR = azimuth;
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if (distance < HRTF_AZIMUTH_REF) {
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nearFieldAzimuthCorrection(azimuth, distance, azimuthL, azimuthR);
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}
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// table parameters
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int az0 = (int)azimuth;
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int az1 = (az0 + 1) % HRTF_AZIMUTHS;
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float frac = azimuth - (float)az0;
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// compute the DC gain correction at each ear
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float gainL = 1.0f;
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float gainR = 1.0f;
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if (distance < HRTF_NEARFIELD_MAX) {
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nearFieldGainCorrection(azimuth, distance, gainL, gainR);
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}
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assert((az0 >= 0) && (az0 < HRTF_AZIMUTHS));
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assert((az1 >= 0) && (az1 < HRTF_AZIMUTHS));
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assert((frac >= 0.0f) && (frac < 1.0f));
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// parameters for table interpolation
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int azL0, azR0, az0;
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int azL1, azR1, az1;
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float fracL, fracR, frac;
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azimuthToIndex(azimuthL, azL0, azL1, fracL);
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azimuthToIndex(azimuthR, azR0, azR1, fracR);
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azimuthToIndex(azimuth, az0, az1, frac);
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// interpolate FIR
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interpolate(firCoef[channel+0], ir_table_table[index][az0][0], ir_table_table[index][az1][0], frac, gain);
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interpolate(firCoef[channel+1], ir_table_table[index][az0][1], ir_table_table[index][az1][1], frac, gain);
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interpolate(firCoef[channel+0], ir_table_table[index][azL0][0], ir_table_table[index][azL1][0], fracL, gain * gainL);
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interpolate(firCoef[channel+1], ir_table_table[index][azR0][1], ir_table_table[index][azR1][1], fracR, gain * gainR);
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// interpolate ITD
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float itd = (1.0f - frac) * itd_table_table[index][az0] + frac * itd_table_table[index][az1];
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@ -832,21 +1023,42 @@ static void setFilters(float firCoef[4][HRTF_TAPS], float bqCoef[5][8], int dela
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}
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//
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// Second biquad implements the distance filter.
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// Second biquad implements the near-field or distance filter.
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//
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distanceBiquad(distance, b0, b1, b2, a1, a2);
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if (distance < HRTF_NEARFIELD_MAX) {
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bqCoef[0][channel+4] = b0;
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bqCoef[1][channel+4] = b1;
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bqCoef[2][channel+4] = b2;
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bqCoef[3][channel+4] = a1;
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bqCoef[4][channel+4] = a2;
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nearFieldFilter(gainL, b0, b1, a1);
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bqCoef[0][channel+5] = b0;
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||||
bqCoef[1][channel+5] = b1;
|
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bqCoef[2][channel+5] = b2;
|
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bqCoef[3][channel+5] = a1;
|
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bqCoef[4][channel+5] = a2;
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bqCoef[0][channel+4] = b0;
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||||
bqCoef[1][channel+4] = b1;
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||||
bqCoef[2][channel+4] = 0.0f;
|
||||
bqCoef[3][channel+4] = a1;
|
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bqCoef[4][channel+4] = 0.0f;
|
||||
|
||||
nearFieldFilter(gainR, b0, b1, a1);
|
||||
|
||||
bqCoef[0][channel+5] = b0;
|
||||
bqCoef[1][channel+5] = b1;
|
||||
bqCoef[2][channel+5] = 0.0f;
|
||||
bqCoef[3][channel+5] = a1;
|
||||
bqCoef[4][channel+5] = 0.0f;
|
||||
|
||||
} else {
|
||||
|
||||
distanceBiquad(distance, b0, b1, b2, a1, a2);
|
||||
|
||||
bqCoef[0][channel+4] = b0;
|
||||
bqCoef[1][channel+4] = b1;
|
||||
bqCoef[2][channel+4] = b2;
|
||||
bqCoef[3][channel+4] = a1;
|
||||
bqCoef[4][channel+4] = a2;
|
||||
|
||||
bqCoef[0][channel+5] = b0;
|
||||
bqCoef[1][channel+5] = b1;
|
||||
bqCoef[2][channel+5] = b2;
|
||||
bqCoef[3][channel+5] = a1;
|
||||
bqCoef[4][channel+5] = a2;
|
||||
}
|
||||
}
|
||||
|
||||
void AudioHRTF::render(int16_t* input, float* output, int index, float azimuth, float distance, float gain, int numFrames) {
|
||||
|
|
|
|||
|
|
@ -23,6 +23,12 @@ static const int HRTF_BLOCK = 240; // block processing size
|
|||
|
||||
static const float HRTF_GAIN = 1.0f; // HRTF global gain adjustment
|
||||
|
||||
// Near-field HRTF
|
||||
static const float HRTF_AZIMUTH_REF = 2.0f; // IRCAM Listen HRTF was recorded at 2 meters
|
||||
static const float HRTF_NEARFIELD_MAX = 1.0f; // distance in meters
|
||||
static const float HRTF_NEARFIELD_MIN = 0.125f; // distance in meters
|
||||
static const float HRTF_HEAD_RADIUS = 0.0875f; // average human head in meters
|
||||
|
||||
class AudioHRTF {
|
||||
|
||||
public:
|
||||
|
|
|
|||
Loading…
Reference in a new issue