Implement Automations for PannerNode and AutioListener

third_party/WebKit/LayoutTests/webaudio/resources/panner-formulas.js

+// For the record, these distance formulas were taken from the OpenAL
+// spec
+// (http://connect.creativelabs.com/openal/Documentation/OpenAL%201.1%20Specification.pdf),
+// not the code.  The Web Audio spec follows the OpenAL formulas.
+
+function linearDistance(panner, x, y, z) {
+    var distance = Math.sqrt(x * x + y * y + z * z);
+    distance = Math.min(distance, panner.maxDistance);
+    var rolloff = panner.rolloffFactor;
+    var gain = (1 - rolloff * (distance - panner.refDistance) / (panner.maxDistance - panner.refDistance));
+
+    return gain;
+}
+
+function inverseDistance(panner, x, y, z) {
+    var distance = Math.sqrt(x * x + y * y + z * z);
+    distance = Math.min(distance, panner.maxDistance);
+    var rolloff = panner.rolloffFactor;
+    var gain = panner.refDistance / (panner.refDistance + rolloff * (distance - panner.refDistance));
+
+    return gain;
+}
+
+function exponentialDistance(panner, x, y, z) {
+    var distance = Math.sqrt(x * x + y * y + z * z);
+    distance = Math.min(distance, panner.maxDistance);
+    var rolloff = panner.rolloffFactor;
+    var gain = Math.pow(distance / panner.refDistance, -rolloff);
+
+    return gain;
+}
+
+// Simple implementations of 3D vectors implemented as a 3-element array.
+
+// x - y
+function vec3Sub(x, y) {
+    var z = new Float32Array(3);
+    z[0] = x[0] - y[0];
+    z[1] = x[1] - y[1];
+    z[2] = x[2] - y[2];
+
+    return z;
+}
+
+// x/|x|
+function vec3Normalize(x) {
+    var mag = Math.hypot(...x);
+    return x.map(function (c) { return c / mag; });
+}
+
+// x == 0?
+function vec3IsZero(x) {
+    return x[0] === 0 && x[1] === 0 && x[2] === 0;
+}
+
+// Vector cross product
+function vec3Cross(u, v) {
+    var cross = new Float32Array(3);
+    cross[0] = u[1] * v[2] - u[2] * v[1];
+    cross[1] = u[2] * v[0] - u[0] * v[2];
+    cross[2] = u[0] * v[1] - u[1] * v[0];
+    return cross;
+}
+
+// Dot product
+function vec3Dot(x, y) {
+    return x[0] * y[0] + x[1] * y[1] + x[2] * y[2];
+}
+
+// a*x, for scalar a
+function vec3Scale(a, x) {
+    return x.map(function (c) { return a * c; });
+}
+
+function calculateAzimuth(source, listener, listenerForward, listenerUp) {
+    var sourceListener = vec3Sub(source, listener);
+
+    if (vec3IsZero(sourceListener))
+        return 0;
+
+    sourceListener = vec3Normalize(sourceListener);
+
+    var listenerRight = vec3Normalize(vec3Cross(listenerForward, listenerUp));
+    var listenerForwardNorm = vec3Normalize(listenerForward);
+
+    var up = vec3Cross(listenerRight, listenerForwardNorm);
+    var upProjection = vec3Dot(sourceListener, up);
+
+    var projectedSource = vec3Normalize(vec3Sub(sourceListener, vec3Scale(upProjection, up)));
+
+    var azimuth = 180 / Math.PI * Math.acos(vec3Dot(projectedSource, listenerRight));
+
+    // Source in front or behind the listener
+    var frontBack = vec3Dot(projectedSource, listenerForwardNorm);
+    if (frontBack < 0)
+        azimuth = 360 - azimuth;
+
+    // Make azimuth relative to "front" and not "right" listener vector.
+    if (azimuth >= 0 && azimuth <= 270)
+        azimuth = 90 - azimuth;
+    else
+        azimuth = 450 - azimuth;
+
+    // We don't need elevation, so we're skipping that computation.
+    return azimuth;
+}
+
+// Map our position angle to the azimuth angle (in degrees).
+//
+// An angle of 0 corresponds to an azimuth of 90 deg; pi, to -90 deg.
+function angleToAzimuth(angle) {
+    return 90 - angle * 180 / Math.PI;
+}
+
+// The gain caused by the EQUALPOWER panning model
+function equalPowerGain(azimuth, numberOfChannels) {
+    var halfPi = Math.PI / 2;
+
+    if (azimuth < -90)
+        azimuth = -180 - azimuth;
+    else
+        azimuth = 180 - azimuth;
+
+    if (numberOfChannels == 1) {
+        var panPosition = (azimuth + 90) / 180;
+
+        var gainL = Math.cos(halfPi * panPosition);
+        var gainR = Math.sin(halfPi * panPosition);
+
+        return { left : gainL, right : gainR };
+    } else {
+        if (azimuth <= 0) {
+            var panPosition = (azimuth + 90) / 90;
+
+            var gainL = Math.cos(halfPi * panPosition);
+            var gainR = Math.sin(halfPi * panPosition);
+
+            return { left : gainL, right : gainR };
+        } else {
+            var panPosition = azimuth / 90;
+
+            var gainL = Math.cos(halfPi * panPosition);
+            var gainR = Math.sin(halfPi * panPosition);
+
+            return { left : gainL, right : gainR };
+        }
+    }
+}
+
+function applyPanner(azimuth, srcL, srcR, numberOfChannels) {
+    var length = srcL.length;
+    var outL = new Float32Array(length);
+    var outR = new Float32Array(length);
+
+    if (numberOfChannels == 1) {
+        for (var k = 0; k < length; ++k) {
+            var gains = equalPowerGain(azimuth[k], numberOfChannels);
+
+            outL[k] = srcL[k] * gains.left;
+            outR[k] = srcR[k] * gains.right;
+        }
+    } else {
+        for (var k = 0; k < length; ++k) {
+            var gains = equalPowerGain(azimuth[k], numberOfChannels);
+
+            if (azimuth[k] <= 0) {
+                outL[k] = srcL[k] + srcR[k] * gains.left;
+                outR[k] = srcR[k] * gains.right;
+            } else {
+                outL[k] = srcL[k] * gains.left;
+                outR[k] = srcR[k] + srcL[k] * gains.right;
+            }
+        }
+    }
+
+    return { left: outL, right: outR };
+}