third_party/WebKit/LayoutTests/webaudio/Oscillator/start-sampling.html - Issue 2623063002: Revert of Sub-sample accurate start of OscillatorNode

Unified Diff: third_party/WebKit/LayoutTests/webaudio/Oscillator/start-sampling.html

Issue 2623063002: Revert of Sub-sample accurate start of OscillatorNode (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master

Patch Set: Created 3 years, 11 months ago

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Index: third_party/WebKit/LayoutTests/webaudio/Oscillator/start-sampling.html

diff --git a/third_party/WebKit/LayoutTests/webaudio/Oscillator/start-sampling.html b/third_party/WebKit/LayoutTests/webaudio/Oscillator/start-sampling.html

deleted file mode 100644

index 800fe084635f5209df402b96cca5ccedb9ff825e..0000000000000000000000000000000000000000

--- a/third_party/WebKit/LayoutTests/webaudio/Oscillator/start-sampling.html

+++ /dev/null

@@ -1,173 +0,0 @@

-<!doctype html>

-<html>

- <head>

- <title>Test Sampling of Oscillator Start Times</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>

- </head>

- <body>

- <script>

- // Experimentation indicates that this sample rate with a 440 Hz

- // oscillator makes for a large difference in the difference signal if the

- // oscillator start isn't sampled correctly.

- let defaultSampleRate = 24000;

- let renderDuration = 1;

- let renderFrames = renderDuration * defaultSampleRate;

- let audit = Audit.createTaskRunner();

- audit.define("basic test small", function (task, should) {

- task.describe("Start oscillator slightly past a sample frame")

- testStartSampling(should, 1.25, {

- error: 1.0842e-4,

- snrThreshold: 84.055

- })

- .then(task.done.bind(task));

- });

- audit.define("basic test big", function (task, should) {

- task.describe("Start oscillator slightly before a sample frame")

- testStartSampling(should, 1.75, {

- error: 1.0838e-4,

- snrThreshold: 84.056

- })

- .then(task.done.bind(task));

- });

- audit.define("diff big offset", function (task, should) {

- task.describe(

- "Test sampling with start offset greater than 1/2 sampling frame"

- );

- // With a sample rate of 24000 Hz, and an oscillator frequency of 440 Hz

- // (the default), a quarter wave delay is 13.636363... frames. This

- // tests the case where the starting time is more than 1/2 frame from

- // the preceding sampling frame. This tests one path of the internal

- // implementation.

- testStartWithGain(should, defaultSampleRate, {

- error: 4.1724e-7,

- snrThreshold: 137.536

- })

- .then(task.done.bind(task));

- });

- audit.define("diff small offset", function (task, should) {

- task.describe(

- "Test sampling with start offset less than 1/2 sampling frame");

- // With a sample rate of 48000 Hz, and an oscillator frequency of 440 Hz

- // (the default), a quarter wave delay is 27.2727... frames. This tests

- // the case where the starting time is less than 1/2 frame from the

- // preceding sampling frame. This tests one path of the internal

- // implementation.

- testStartWithGain(should, 48000, {

- error: 4.1724e-7,

- snrThreshold: 137.536

- })

- .then(task.done.bind(task));

- });

- function testStartSampling(should, startFrame, thresholds) {

- // Start the oscillator in the middle of a sample frame and compare

- // against the theoretical result.

- let context = new OfflineAudioContext(1, renderFrames,

- defaultSampleRate);

- let osc = context.createOscillator();

- osc.connect(context.destination);

- osc.start(startFrame / context.sampleRate);

- return context.startRendering().then(function (result) {

- let actual = result.getChannelData(0);

- let expected = new Array(actual.length);

- expected.fill(0);

- // The expected curve is

- //

- // sin(2*pi*f*(t-t0))

- //

- // where f is the oscillator frequency and t0 is the start time.

- let actualStart = Math.ceil(startFrame);

- let omega = 2 * Math.PI * osc.frequency.value / context.sampleRate;

- for (let k = actualStart; k < actual.length; ++k) {

- expected[k] = Math.sin(omega * (k - startFrame));

- }

- should(actual, "Oscillator.start(" + startFrame + " frames)")

- .beCloseToArray(expected, {

- absoluteThreshold: thresholds.error

- });

- let snr = 10 * Math.log10(computeSNR(actual, expected));

- should(snr, "SNR (dB)")

- .beGreaterThanOrEqualTo(thresholds.snrThreshold);

- })

- }

- function testStartWithGain(should, sampleRate, thresholds) {

- // Test consists of starting a cosine wave with a quarter wavelength

- // delay and comparing that with a sine wave that has the initial

- // quarter wavelength zeroed out. These should be equal.

- let context = new OfflineAudioContext(3, renderFrames, sampleRate);

- let osc = context.createOscillator();

- let merger = context.createChannelMerger(3);

- merger.connect(context.destination);

- // Start the cosine oscillator at this time. This means the wave starts

- // at frame 13.636363....

- let quarterWaveTime = (1 / 4) / osc.frequency.value;

- // Sine wave oscillator with gain term to zero out the initial quarter

- // wave length of the output.

- let g = context.createGain();

- g.gain.setValueAtTime(0, 0);

- g.gain.setValueAtTime(1, quarterWaveTime);

- osc.connect(g);

- g.connect(merger, 0, 2);

- g.connect(merger, 0, 0);

- // Cosine wave oscillator with starting after a quarter wave length.

- let osc2 = context.createOscillator();

- // Creates a cosine wave.

- let wave = context.createPeriodicWave(

- Float32Array.from([0, 1]),

- Float32Array.from([0, 0]));

- osc2.setPeriodicWave(wave);

- osc2.connect(merger, 0, 1);

- // A gain inverter so subtract the two waveforms.

- let inverter = context.createGain();

- inverter.gain.value = -1;

- osc2.connect(inverter);

- inverter.connect(merger, 0, 0);

- osc.start();

- osc2.start(quarterWaveTime);

- return context.startRendering().then(function (result) {

- // Channel 0 = diff

- // Channel 1 = osc with start

- // Channel 2 = osc with gain

- // Channel 0 should be very close to 0.

- // Channel 1 should match channel 2 very closely.

- let diff = result.getChannelData(0);

- let oscStart = result.getChannelData(1);

- let oscGain = result.getChannelData(2);

- let snr = 10 * Math.log10(computeSNR(oscStart, oscGain));

- should(oscStart, "Delayed cosine oscillator at sample rate " + sampleRate)

- .beCloseToArray(oscGain, {

- absoluteThreshold: thresholds.error

- });

- should(snr, "SNR (dB)")

- .beGreaterThanOrEqualTo(thresholds.snrThreshold);

- });

- }

- audit.run();

- </script>

- </body>

-</html>

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