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Diffstat (limited to 'testing/web-platform/tests/webaudio/the-audio-api/the-iirfilternode-interface/iirfilter-getFrequencyResponse.html')
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diff --git a/testing/web-platform/tests/webaudio/the-audio-api/the-iirfilternode-interface/iirfilter-getFrequencyResponse.html b/testing/web-platform/tests/webaudio/the-audio-api/the-iirfilternode-interface/iirfilter-getFrequencyResponse.html new file mode 100644 index 0000000000..c98555f161 --- /dev/null +++ b/testing/web-platform/tests/webaudio/the-audio-api/the-iirfilternode-interface/iirfilter-getFrequencyResponse.html @@ -0,0 +1,159 @@ +<!DOCTYPE html> +<html> + <head> + <title> + Test IIRFilter getFrequencyResponse() functionality + </title> + <script src="/resources/testharness.js"></script> + <script src="/resources/testharnessreport.js"></script> + <script src="../../resources/audit-util.js"></script> + <script src="../../resources/audit.js"></script> + <script src="../../resources/biquad-filters.js"></script> + </head> + <body> + <script id="layout-test-code"> + let sampleRate = 48000; + // Some short duration; we're not actually looking at the rendered output. + let testDurationSec = 0.01; + + // Number of frequency samples to take. + let numberOfFrequencies = 1000; + + let audit = Audit.createTaskRunner(); + + + // Compute a set of linearly spaced frequencies. + function createFrequencies(nFrequencies, sampleRate) { + let frequencies = new Float32Array(nFrequencies); + let nyquist = sampleRate / 2; + let freqDelta = nyquist / nFrequencies; + + for (let k = 0; k < nFrequencies; ++k) { + frequencies[k] = k * freqDelta; + } + + return frequencies; + } + + audit.define('1-pole IIR', (task, should) => { + let context = new OfflineAudioContext( + 1, testDurationSec * sampleRate, sampleRate); + + let iir = context.createIIRFilter([1], [1, -0.9]); + let frequencies = + createFrequencies(numberOfFrequencies, context.sampleRate); + + let iirMag = new Float32Array(numberOfFrequencies); + let iirPhase = new Float32Array(numberOfFrequencies); + let trueMag = new Float32Array(numberOfFrequencies); + let truePhase = new Float32Array(numberOfFrequencies); + + // The IIR filter is + // H(z) = 1/(1 - 0.9*z^(-1)). + // + // The frequency response is + // H(exp(j*w)) = 1/(1 - 0.9*exp(-j*w)). + // + // Thus, the magnitude is + // |H(exp(j*w))| = 1/sqrt(1.81-1.8*cos(w)). + // + // The phase is + // arg(H(exp(j*w)) = atan(0.9*sin(w)/(.9*cos(w)-1)) + + let frequencyScale = Math.PI / (sampleRate / 2); + + for (let k = 0; k < frequencies.length; ++k) { + let omega = frequencyScale * frequencies[k]; + trueMag[k] = 1 / Math.sqrt(1.81 - 1.8 * Math.cos(omega)); + truePhase[k] = + Math.atan(0.9 * Math.sin(omega) / (0.9 * Math.cos(omega) - 1)); + } + + iir.getFrequencyResponse(frequencies, iirMag, iirPhase); + + // Thresholds were experimentally determined. + should(iirMag, '1-pole IIR Magnitude Response') + .beCloseToArray(trueMag, {absoluteThreshold: 2.8611e-6}); + should(iirPhase, '1-pole IIR Phase Response') + .beCloseToArray(truePhase, {absoluteThreshold: 1.7882e-7}); + + task.done(); + }); + + audit.define('compare IIR and biquad', (task, should) => { + // Create an IIR filter equivalent to the biquad filter. Compute the + // frequency response for both and verify that they are the same. + let context = new OfflineAudioContext( + 1, testDurationSec * sampleRate, sampleRate); + + let biquad = context.createBiquadFilter(); + let coef = createFilter( + biquad.type, biquad.frequency.value / (context.sampleRate / 2), + biquad.Q.value, biquad.gain.value); + + let iir = context.createIIRFilter( + [coef.b0, coef.b1, coef.b2], [1, coef.a1, coef.a2]); + + let frequencies = + createFrequencies(numberOfFrequencies, context.sampleRate); + let biquadMag = new Float32Array(numberOfFrequencies); + let biquadPhase = new Float32Array(numberOfFrequencies); + let iirMag = new Float32Array(numberOfFrequencies); + let iirPhase = new Float32Array(numberOfFrequencies); + + biquad.getFrequencyResponse(frequencies, biquadMag, biquadPhase); + iir.getFrequencyResponse(frequencies, iirMag, iirPhase); + + // Thresholds were experimentally determined. + should(iirMag, 'IIR Magnitude Response').beCloseToArray(biquadMag, { + absoluteThreshold: 2.7419e-5 + }); + should(iirPhase, 'IIR Phase Response').beCloseToArray(biquadPhase, { + absoluteThreshold: 2.7657e-5 + }); + + task.done(); + }); + + audit.define( + { + label: 'getFrequencyResponse', + description: 'Test out-of-bounds frequency values' + }, + (task, should) => { + let context = new OfflineAudioContext(1, 1, sampleRate); + let filter = new IIRFilterNode( + context, {feedforward: [1], feedback: [1, -.9]}); + + // Frequencies to test. These are all outside the valid range of + // frequencies of 0 to Nyquist. + let freq = new Float32Array(2); + freq[0] = -1; + freq[1] = context.sampleRate / 2 + 1; + + let mag = new Float32Array(freq.length); + let phase = new Float32Array(freq.length); + + filter.getFrequencyResponse(freq, mag, phase); + + // Verify that the returned magnitude and phase entries are alL NaN + // since the frequencies are outside the valid range + for (let k = 0; k < mag.length; ++k) { + should(mag[k], + 'Magnitude response at frequency ' + freq[k]) + .beNaN(); + } + + for (let k = 0; k < phase.length; ++k) { + should(phase[k], + 'Phase response at frequency ' + freq[k]) + .beNaN(); + } + + task.done(); + }); + + audit.run(); + </script> + </body> +</html> |