| <!DOCTYPE html> |
| <html> |
| <head> |
| <title> |
| Test Custom 440 Hz Oscillator |
| </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'>let sampleRate = 48000; |
| |
| // Minimum allowed SNR between the actual oscillator and the expected |
| // result. Experimentally determined. |
| let snrThreshold = 59.280; |
| // Max absolute difference between actual and expected oscillator |
| // outputs. Experimentally determined. |
| let maxDiffThreshold = 1.5640e-3; |
| |
| let audit = Audit.createTaskRunner(); |
| |
| // Test that two ways of creating a 440-Hz sine wave produce the same |
| // results, within some tolerance. |
| |
| audit.define('440 Hz Osc', (task, should) => { |
| // 3-channel context: channel 0 = actual output; channel 1 = expected |
| // output, channel 2 = difference between channels 0 and 1. |
| let context = new OfflineAudioContext(3, sampleRate, sampleRate); |
| let merger = new ChannelMergerNode( |
| context, {numberOfInputs: context.destination.channelCount}); |
| merger.connect(context.destination); |
| |
| // Create a 440 Hz oscillator in following way. Use a PeriodicWave with |
| // a single harmonic value of 440 and use that in an oscillator with |
| // fundamental frequeqncy of 1 Hz. This should produce a 440 Hz sine |
| // wave. This is the test signal. |
| let imag = new Float32Array(512); |
| imag[440] = 1; |
| let wave440 = |
| new PeriodicWave(context, {imag: imag, disableNormaliztion: true}); |
| |
| let oscTest = |
| new OscillatorNode(context, {frequency: 1, periodicWave: wave440}); |
| |
| // Create a 440 Hz oscillator by specifying a frequency of 440 Hz. We |
| // use a periodicWave for this so we can disable normalization. |
| let oscRef = new OscillatorNode(context, { |
| frequency: 440, |
| periodocWave: new PeriodicWave( |
| context, {imag: [0, 1], disableNormaliztion: true}) |
| }); |
| |
| oscTest.connect(merger, 0, 0); |
| oscRef.connect(merger, 0, 1); |
| |
| // Compute the difference of the two signals |
| let neg = new GainNode(context, {gain: -1}); |
| neg.connect(merger, 0, 2); |
| |
| oscTest.connect(merger, 0, 2); |
| oscRef.connect(neg); |
| |
| oscTest.start(); |
| oscRef.start(); |
| |
| context.startRendering() |
| .then(result => { |
| // Extract the actual output, the reference output and the |
| // difference signal from the rendered data. |
| actual = result.getChannelData(0); |
| ref = result.getChannelData(1); |
| diff = result.getChannelData(2); |
| |
| // The actual and reference signals should be close, and the SNR |
| // should be high. |
| should(actual, 'Test oscillator output').beCloseToArray( |
| ref, {absoluteThreshold: maxDiffThreshold}); |
| |
| let snr = 10 * Math.log10(computeSNR(actual, ref)); |
| should(snr, 'SNR').beGreaterThanOrEqualTo(snrThreshold); |
| |
| }) |
| .then(() => task.done()); |
| }); |
| |
| audit.run(); |
| </script> |
| </body> |
| </html> |
