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let StereoPannerTest = (function() {
// Constants
let PI_OVER_TWO = Math.PI * 0.5;
// Use a power of two to eliminate any round-off when converting frames to
// time.
let gSampleRate = 32768;
// Time step when each panner node starts. Make sure this is on a frame boundary.
let gTimeStep = Math.floor(0.001 * gSampleRate) / gSampleRate;
// How many panner nodes to create for the test
let gNodesToCreate = 100;
// Total render length for all of our nodes.
let gRenderLength = gTimeStep * (gNodesToCreate + 1) + gSampleRate;
// Calculates channel gains based on equal power panning model.
// See: http://webaudio.github.io/web-audio-api/#panning-algorithm
function getChannelGain(pan, numberOfChannels) {
// The internal panning clips the pan value between -1, 1.
pan = Math.min(Math.max(pan, -1), 1);
let gainL, gainR;
// Consider number of channels and pan value's polarity.
if (numberOfChannels == 1) {
let panRadian = (pan * 0.5 + 0.5) * PI_OVER_TWO;
gainL = Math.cos(panRadian);
gainR = Math.sin(panRadian);
} else {
let panRadian = (pan <= 0 ? pan + 1 : pan) * PI_OVER_TWO;
if (pan <= 0) {
gainL = 1 + Math.cos(panRadian);
gainR = Math.sin(panRadian);
} else {
gainL = Math.cos(panRadian);
gainR = 1 + Math.sin(panRadian);
}
}
return {gainL: gainL, gainR: gainR};
}
/**
* Test implementation class.
* @param {Object} options Test options
* @param {Object} options.description Test description
* @param {Object} options.numberOfInputChannels Number of input channels
*/
function Test(should, options) {
// Primary test flag.
this.success = true;
this.should = should;
this.context = null;
this.prefix = options.prefix;
this.numberOfInputChannels = (options.numberOfInputChannels || 1);
switch (this.numberOfInputChannels) {
case 1:
this.description = 'Test for mono input';
break;
case 2:
this.description = 'Test for stereo input';
break;
}
// Onset time position of each impulse.
this.onsets = [];
// Pan position value of each impulse.
this.panPositions = [];
// Locations of where the impulses aren't at the expected locations.
this.errors = [];
// The index of the current impulse being verified.
this.impulseIndex = 0;
// The max error we allow between the rendered impulse and the
// expected value. This value is experimentally determined. Set
// to 0 to make the test fail to see what the actual error is.
this.maxAllowedError = 1.284318e-7;
// Max (absolute) error and the index of the maxima for the left
// and right channels.
this.maxErrorL = 0;
this.maxErrorR = 0;
this.maxErrorIndexL = 0;
this.maxErrorIndexR = 0;
// The maximum value to use for panner pan value. The value will range from
// -panLimit to +panLimit.
this.panLimit = 1.0625;
}
Test.prototype.init = function() {
this.context = new OfflineAudioContext(2, gRenderLength, gSampleRate);
};
// Prepare an audio graph for testing. Create multiple impulse generators and
// panner nodes, then play them sequentially while varying the pan position.
Test.prototype.prepare = function() {
let impulse;
let impulseLength = Math.round(gTimeStep * gSampleRate);
let sources = [];
let panners = [];
// Moves the pan value for each panner by pan step unit from -2 to 2.
// This is to check if the internal panning value is clipped properly.
let panStep = (2 * this.panLimit) / (gNodesToCreate - 1);
if (this.numberOfInputChannels === 1) {
impulse = createImpulseBuffer(this.context, impulseLength);
} else {
impulse = createStereoImpulseBuffer(this.context, impulseLength);
}
for (let i = 0; i < gNodesToCreate; i++) {
sources[i] = this.context.createBufferSource();
panners[i] = this.context.createStereoPanner();
sources[i].connect(panners[i]);
panners[i].connect(this.context.destination);
sources[i].buffer = impulse;
panners[i].pan.value = this.panPositions[i] = panStep * i - this.panLimit;
// Store the onset time position of impulse.
this.onsets[i] = gTimeStep * i;
sources[i].start(this.onsets[i]);
}
};
Test.prototype.verify = function() {
let chanL = this.renderedBufferL;
let chanR = this.renderedBufferR;
for (let i = 0; i < chanL.length; i++) {
// Left and right channels must start at the same instant.
if (chanL[i] !== 0 || chanR[i] !== 0) {
// Get amount of error between actual and expected gain.
let expected = getChannelGain(
this.panPositions[this.impulseIndex], this.numberOfInputChannels);
let errorL = Math.abs(chanL[i] - expected.gainL);
let errorR = Math.abs(chanR[i] - expected.gainR);
if (errorL > this.maxErrorL) {
this.maxErrorL = errorL;
this.maxErrorIndexL = this.impulseIndex;
}
if (errorR > this.maxErrorR) {
this.maxErrorR = errorR;
this.maxErrorIndexR = this.impulseIndex;
}
// Keep track of the impulses that didn't show up where we expected
// them to be.
let expectedOffset =
timeToSampleFrame(this.onsets[this.impulseIndex], gSampleRate);
if (i != expectedOffset) {
this.errors.push({actual: i, expected: expectedOffset});
}
this.impulseIndex++;
}
}
};
Test.prototype.showResult = function() {
this.should(this.impulseIndex, this.prefix + 'Number of impulses found')
.beEqualTo(gNodesToCreate);
this.should(
this.errors.length,
this.prefix + 'Number of impulse at the wrong offset')
.beEqualTo(0);
this.should(this.maxErrorL, this.prefix + 'Left channel error magnitude')
.beLessThanOrEqualTo(this.maxAllowedError);
this.should(this.maxErrorR, this.prefix + 'Right channel error magnitude')
.beLessThanOrEqualTo(this.maxAllowedError);
};
Test.prototype.run = function() {
this.init();
this.prepare();
return this.context.startRendering().then(renderedBuffer => {
this.renderedBufferL = renderedBuffer.getChannelData(0);
this.renderedBufferR = renderedBuffer.getChannelData(1);
this.verify();
this.showResult();
});
};
return {
create: function(should, options) {
return new Test(should, options);
}
};
})();
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