| <!doctype html> |
| <html> |
| <head> |
| <script src="../resources/js-test.js"></script> |
| <script src="resources/compatibility.js"></script> |
| <script src="resources/audio-testing.js"></script> |
| <title>Test OscillatorNode with Negative Frequency</title> |
| </head> |
| |
| <body> |
| <script> |
| description("Test OscillatorNode with Negative Frequency."); |
| window.jsTestIsAsync = true; |
| |
| // Some arbitrary sample rate for the offline context. |
| var sampleRate = 48000; |
| var renderDuration = 1; |
| var renderFrames = renderDuration * sampleRate; |
| |
| var audit = Audit.createTaskRunner(); |
| |
| audit.defineTask("sine", function (done) { |
| runTest({ |
| message: "Sum of positive and negative frequency sine oscillators", |
| type: "sine", |
| threshold: 4.7684e-7 |
| }).then(done); |
| }); |
| |
| audit.defineTask("square", function (done) { |
| runTest({ |
| message: "Sum of positive and negative frequency square oscillators", |
| type: "square", |
| threshold: 4.4108e-6 |
| }).then(done); |
| }); |
| |
| audit.defineTask("sawtooth", function (done) { |
| runTest({ |
| message: "Sum of positive and negative frequency sawtooth oscillators", |
| type: "sawtooth", |
| threshold: 4.3735e-6 |
| }).then(done); |
| }); |
| |
| audit.defineTask("triangle", function (done) { |
| runTest({ |
| message: "Sum of positive and negative frequency triangle oscillators", |
| type: "triangle", |
| threshold: 3.5763e-7 |
| }).then(done); |
| }); |
| |
| audit.defineTask("auto-sawtooth", function (done) { |
| runTest({ |
| 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: 4.1202e-6 |
| }).then(done); |
| }); |
| |
| audit.defineTask("periodic-wave", function (done) { |
| // 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. |
| var context = new OfflineAudioContext(2, renderFrames, sampleRate); |
| |
| var oscPositive = context.createOscillator(); |
| var 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. |
| var real = [0, 1, 1]; |
| var imag = [0, 1, 1]; |
| |
| var wavePositive = context.createPeriodicWave( |
| Float32Array.from(real), |
| Float32Array.from(imag)); |
| var 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; |
| |
| var merger = context.createChannelMerger(2); |
| var 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) { |
| var expected = buffer.getChannelData(0); |
| var actual = buffer.getChannelData(1); |
| |
| Should("Sum of positive and negative frequency custom oscillators", |
| actual, { |
| precision: 6 |
| }) |
| .beCloseToArray(expected, 4.7684e-7); |
| }).then(done); |
| }); |
| |
| |
| // All done! |
| audit.defineTask("finish", function (done) { |
| finishJSTest(); |
| done(); |
| }); |
| |
| audit.runTasks(); |
| |
| function runTest(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. |
| var context = new OfflineAudioContext(1, renderFrames, sampleRate); |
| |
| var oscPositive = context.createOscillator(); |
| var oscNegative = context.createOscillator(); |
| |
| oscPositive.type = options.type; |
| oscNegative.type = oscPositive.type; |
| |
| if (options.automation) { |
| var {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) { |
| var result = buffer.getChannelData(0); |
| |
| var zero = new Float32Array(result.length); |
| zero.fill(0); |
| Should(options.message, result, { |
| verbose: true |
| }).beCloseToArray(zero, options.threshold || 0); |
| }); |
| } |
| </script> |
| </body> |
| </html> |
