| <!DOCTYPE html> |
| <html> |
| <head> |
| <title> |
| Test OscillatorNode with Negative Frequency |
| </title> |
| <script src="../../imported/w3c/web-platform-tests/resources/testharness.js"></script> |
| <script src="../../resources/testharnessreport.js"></script> |
| <script src="../resources/audit-util.js"></script> |
| <script src="../resources/audit.js"></script> |
| </head> |
| <body> |
| <script id="layout-test-code"> |
| // Some arbitrary sample rate for the offline context. But it MUST be |
| // at least twice the oscillator frequency that we're using for the |
| // test. (Currently 440 Hz.) |
| let sampleRate = 16000; |
| |
| // A fairly arbitrary duration that should have at least 1-2 sample |
| // periods of the oscillator (at a nominal 440 Hz). |
| let renderDuration = 0.1; |
| let renderFrames = renderDuration * sampleRate; |
| |
| let audit = Audit.createTaskRunner(); |
| |
| audit.define('sine', (task, should) => { |
| runTest(should, { |
| message: 'Sum of positive and negative frequency sine oscillators', |
| type: 'sine', |
| threshold: 1.5349e-6 |
| }).then(() => task.done()); |
| }); |
| |
| audit.define('square', (task, should) => { |
| runTest(should, { |
| message: 'Sum of positive and negative frequency square oscillators', |
| type: 'square', |
| threshold: 1.1496e-5 |
| }).then(() => task.done()); |
| }); |
| |
| audit.define('sawtooth', (task, should) => { |
| runTest(should, { |
| message: |
| 'Sum of positive and negative frequency sawtooth oscillators', |
| type: 'sawtooth', |
| threshold: 1.1506e-5 |
| }).then(() => task.done()); |
| }); |
| |
| audit.define('triangle', (task, should) => { |
| runTest(should, { |
| message: |
| 'Sum of positive and negative frequency triangle oscillators', |
| type: 'triangle', |
| threshold: 1.0133e-5 |
| }).then(() => task.done()); |
| }); |
| |
| audit.define('auto-sawtooth', (task, should) => { |
| runTest(should, { |
| message: |
| 'Sum of positive and negative frequency-ramped sawtooth oscillators', |
| type: 'sawtooth', |
| automation: { |
| type: 'linearRampToValueAtTime', |
| startTime: 0, |
| endTime: renderDuration / 2, |
| startFrequency: 440, |
| endFrequency: sampleRate / 4 |
| }, |
| threshold: 1.2368e-6 |
| }).then(() => task.done()); |
| }); |
| |
| audit.define('periodic-wave', (task, should) => { |
| // Test negative frequencies for a custom oscillator. Two channels are |
| // needed for the context; one for the expected result, and one for the |
| // actual, as explained below. |
| let context = new OfflineAudioContext(2, renderFrames, sampleRate); |
| |
| let oscPositive = context.createOscillator(); |
| let oscNegative = context.createOscillator(); |
| |
| // The Fourier coefficients for our custom oscillator. The actual |
| // values not important. The waveform for our custom oscillator is |
| // |
| // x(t) = sum(real[k]*cos(2*%pi*f*k/Fs), k, 1) |
| // + sum(imag[k]*sin(2*%pi*f*k/Fs), k, 0) |
| // |
| // With a negative frequency we have |
| // |
| // x(t) = sum(real[k]*cos(2*%pi*(-f)*k/Fs), k, 1) |
| // + sum(imag[k]*sin(2*%pi*(-f)*k/Fs), k, 0) |
| // |
| // = sum(real[k]*cos(2*%pi*f*k/Fs), k, 1) |
| // + sum((-imag[k])*sin(2*%pi*f*k/Fs), k, 0) |
| // |
| // That is, when the frequency is inverted, it behaves as if the |
| // coefficients of the imaginary part are inverted. |
| // |
| // Thus, the test is to create two custom oscillators. The second |
| // osillator uses the same PeriodicWave as the first except the |
| // imaginary coefficients are inverted. This second oscillator also |
| // gets a negative frequency. The combination of the two results in an |
| // oscillator that is the same as the first with gain of 2. |
| let real = [0, 1, 1]; |
| let imag = [0, 1, 1]; |
| |
| let wavePositive = context.createPeriodicWave( |
| Float32Array.from(real), Float32Array.from(imag)); |
| let waveNegative = context.createPeriodicWave( |
| Float32Array.from(real), Float32Array.from(imag.map(x => -x))); |
| |
| oscPositive.setPeriodicWave(wavePositive); |
| oscNegative.setPeriodicWave(waveNegative); |
| |
| oscPositive.frequency.value = 440; |
| oscNegative.frequency.value = -oscPositive.frequency.value; |
| |
| let merger = context.createChannelMerger(2); |
| let gain = context.createGain(); |
| |
| // As explained above, the expected result should be positive frequency |
| // oscillator but with a gain of 2. |
| gain.gain.value = 2; |
| oscPositive.connect(gain); |
| gain.connect(merger, 0, 0); |
| |
| // Sum the positive and negative frequency oscillators by using the same |
| // input to the merger. |
| oscPositive.connect(merger, 0, 1); |
| oscNegative.connect(merger, 0, 1); |
| |
| merger.connect(context.destination); |
| |
| oscPositive.start(); |
| oscNegative.start(); |
| |
| context.startRendering() |
| .then(function(buffer) { |
| let expected = buffer.getChannelData(0); |
| let actual = buffer.getChannelData(1); |
| |
| should( |
| actual, |
| 'Sum of positive and negative frequency custom oscillators') |
| .beCloseToArray(expected, {absoluteThreshold: 2.2352e-6}); |
| }) |
| .then(() => task.done()); |
| }); |
| |
| audit.run(); |
| |
| function runTest(should, options) { |
| // To test if negative frequencies work, create two oscillators. One |
| // has a positive frequency and the other has a negative frequency. |
| // Sum the oscillator outputs; the output should be zero because all of |
| // the builtin oscillator types are odd functions of frequency. |
| let context = new OfflineAudioContext(1, renderFrames, sampleRate); |
| |
| let oscPositive = context.createOscillator(); |
| let oscNegative = context.createOscillator(); |
| |
| oscPositive.type = options.type; |
| oscNegative.type = oscPositive.type; |
| |
| if (options.automation) { |
| let {type, startTime, endTime, startFrequency, endFrequency} = |
| options.automation; |
| oscPositive.frequency.setValueAtTime(startFrequency, startTime); |
| oscPositive.frequency[type](endFrequency, endTime) |
| |
| oscNegative.frequency.setValueAtTime(-startFrequency, startTime); |
| oscNegative.frequency[type](-endFrequency, endTime) |
| } else { |
| oscPositive.frequency.value = 440; |
| oscNegative.frequency.value = -oscPositive.frequency.value; |
| } |
| |
| oscPositive.connect(context.destination); |
| oscNegative.connect(context.destination); |
| |
| oscPositive.start(); |
| oscNegative.start(); |
| |
| return context.startRendering().then(function(buffer) { |
| let result = buffer.getChannelData(0); |
| |
| should(result, options.message) |
| .beCloseToArray( |
| new Float32Array(result.length), |
| {absoluteThreshold: options.threshold || 0}); |
| }); |
| } |
| </script> |
| </body> |
| </html> |
