chromium/src/third_party/blink/web_tests/external/wpt/webaudio/the-audio-api/the-gainnode-interface/gain.html - manifest_repos/chromium_src - Git at Google

 <!DOCTYPE html>
 <html>
   <head>
     <title>
       Basic GainNode Functionality
     </title>
     <script src="/resources/testharness.js"></script>
     <script src="/resources/testharnessreport.js"></script>
     <script src="/webaudio/resources/audit-util.js"></script>
     <script src="/webaudio/resources/audit.js"></script>
   </head>
   <body>
     <script id="layout-test-code">
       // Tests that GainNode is properly scaling the gain.  We'll render 11
       // notes, starting at a gain of 1.0, decreasing in gain by 0.1.  The 11th
       // note will be of gain 0.0, so it should be silent (at the end in the
       // rendered output).

       let audit = Audit.createTaskRunner();

       // Use a power of two to eliminate any round-off when converting frame to
       // time.
       let sampleRate = 32768;
       // Make sure the buffer duration and spacing are all exact frame lengths
       // so that the note spacing is also on frame boundaries to eliminate
       // sub-sample accurate start of a ABSN.
       let bufferDurationSeconds = Math.floor(0.125 * sampleRate) / sampleRate;
       let numberOfNotes = 11;
       // Leave about 20ms of silence, being sure this is an exact frame
       // duration.
       let noteSilence = Math.floor(0.020 * sampleRate) / sampleRate;
       let noteSpacing = bufferDurationSeconds + noteSilence;

       let lengthInSeconds = numberOfNotes * noteSpacing;

       let context = 0;
       let sinWaveBuffer = 0;

       // Create a stereo AudioBuffer of duration |lengthInSeconds| consisting of
       // a pure sine wave with the given |frequency|.  Both channels contain the
       // same data.
       function createSinWaveBuffer(lengthInSeconds, frequency) {
         let audioBuffer =
             context.createBuffer(2, lengthInSeconds * sampleRate, sampleRate);

         let n = audioBuffer.length;
         let channelL = audioBuffer.getChannelData(0);
         let channelR = audioBuffer.getChannelData(1);

         for (let i = 0; i < n; ++i) {
           channelL[i] = Math.sin(frequency * 2.0 * Math.PI * i / sampleRate);
           channelR[i] = channelL[i];
         }

         return audioBuffer;
       }

       function playNote(time, gain, merger) {
         let source = context.createBufferSource();
         source.buffer = sinWaveBuffer;

         let gainNode = context.createGain();
         gainNode.gain.value = gain;

         let sourceSplitter = context.createChannelSplitter(2);
         let gainSplitter = context.createChannelSplitter(2);

         // Split the stereo channels from the source output and the gain output
         // and merge them into the desired channels of the merger.
         source.connect(gainNode).connect(gainSplitter);
         source.connect(sourceSplitter);

         gainSplitter.connect(merger, 0, 0);
         gainSplitter.connect(merger, 1, 1);
         sourceSplitter.connect(merger, 0, 2);
         sourceSplitter.connect(merger, 1, 3);

         source.start(time);
       }

       audit.define(
           {label: 'create context', description: 'Create context for test'},
           function(task, should) {
             // Create offline audio context.
             context = new OfflineAudioContext(
                 4, sampleRate * lengthInSeconds, sampleRate);
             task.done();
           });

       audit.define(
           {label: 'test', description: 'GainNode functionality'},
           function(task, should) {
             let merger = new ChannelMergerNode(
                 context, {numberOfInputs: context.destination.channelCount});
             merger.connect(context.destination);

             // Create a buffer for a short "note".
             sinWaveBuffer = createSinWaveBuffer(bufferDurationSeconds, 880.0);

             let startTimes = [];
             let gainValues = [];

             // Render 11 notes, starting at a gain of 1.0, decreasing in gain by
             // 0.1. The last note will be of gain 0.0, so shouldn't be
             // perceptible in the rendered output.
             for (let i = 0; i < numberOfNotes; ++i) {
               let time = i * noteSpacing;
               let gain = 1.0 - i / (numberOfNotes - 1);
               startTimes.push(time);
               gainValues.push(gain);
               playNote(time, gain, merger);
             }

             context.startRendering()
                 .then(buffer => {
                   let actual0 = buffer.getChannelData(0);
                   let actual1 = buffer.getChannelData(1);
                   let reference0 = buffer.getChannelData(2);
                   let reference1 = buffer.getChannelData(3);

                   // It's ok to a frame too long since the sine pulses are
                   // followed by silence.
                   let bufferDurationFrames =
                       Math.ceil(bufferDurationSeconds * context.sampleRate);

                   // Apply the gains to the reference signal.
                   for (let k = 0; k < startTimes.length; ++k) {
                     // It's ok to be a frame early because the sine pulses are
                     // preceded by silence.
                     let startFrame =
                         Math.floor(startTimes[k] * context.sampleRate);
                     let gain = gainValues[k];
                     for (let n = 0; n < bufferDurationFrames; ++n) {
                       reference0[startFrame + n] *= gain;
                       reference1[startFrame + n] *= gain;
                     }
                   }

                   // Verify the channels are clsoe to the reference.
                   should(actual0, 'Left output from gain node')
                       .beCloseToArray(
                           reference0, {relativeThreshold: 1.1877e-7});
                   should(actual1, 'Right output from gain node')
                       .beCloseToArray(
                           reference1, {relativeThreshold: 1.1877e-7});

                   // Test the SNR too for both channels.
                   let snr0 = 10 * Math.log10(computeSNR(actual0, reference0));
                   let snr1 = 10 * Math.log10(computeSNR(actual1, reference1));
                   should(snr0, 'Left SNR (in dB)')
                       .beGreaterThanOrEqualTo(148.71);
                   should(snr1, 'Right SNR (in dB)')
                       .beGreaterThanOrEqualTo(148.71);
                 })
                 .then(() => task.done());
             ;
           });

       audit.run();
     </script>
   </body>
 </html>
	<!DOCTYPE html>
	<html>
	<head>
	<title>
	Basic GainNode Functionality
	</title>
	<script src="/resources/testharness.js"></script>
	<script src="/resources/testharnessreport.js"></script>
	<script src="/webaudio/resources/audit-util.js"></script>
	<script src="/webaudio/resources/audit.js"></script>
	</head>
	<body>
	<script id="layout-test-code">
	// Tests that GainNode is properly scaling the gain. We'll render 11
	// notes, starting at a gain of 1.0, decreasing in gain by 0.1. The 11th
	// note will be of gain 0.0, so it should be silent (at the end in the
	// rendered output).

	let audit = Audit.createTaskRunner();

	// Use a power of two to eliminate any round-off when converting frame to
	// time.
	let sampleRate = 32768;
	// Make sure the buffer duration and spacing are all exact frame lengths
	// so that the note spacing is also on frame boundaries to eliminate
	// sub-sample accurate start of a ABSN.
	let bufferDurationSeconds = Math.floor(0.125 * sampleRate) / sampleRate;
	let numberOfNotes = 11;
	// Leave about 20ms of silence, being sure this is an exact frame
	// duration.
	let noteSilence = Math.floor(0.020 * sampleRate) / sampleRate;
	let noteSpacing = bufferDurationSeconds + noteSilence;

	let lengthInSeconds = numberOfNotes * noteSpacing;

	let context = 0;
	let sinWaveBuffer = 0;

	// Create a stereo AudioBuffer of duration \|lengthInSeconds\| consisting of
	// a pure sine wave with the given \|frequency\|. Both channels contain the
	// same data.
	function createSinWaveBuffer(lengthInSeconds, frequency) {
	let audioBuffer =
	context.createBuffer(2, lengthInSeconds * sampleRate, sampleRate);

	let n = audioBuffer.length;
	let channelL = audioBuffer.getChannelData(0);
	let channelR = audioBuffer.getChannelData(1);

	for (let i = 0; i < n; ++i) {
	channelL[i] = Math.sin(frequency * 2.0 * Math.PI * i / sampleRate);
	channelR[i] = channelL[i];
	}

	return audioBuffer;
	}

	function playNote(time, gain, merger) {
	let source = context.createBufferSource();
	source.buffer = sinWaveBuffer;

	let gainNode = context.createGain();
	gainNode.gain.value = gain;

	let sourceSplitter = context.createChannelSplitter(2);
	let gainSplitter = context.createChannelSplitter(2);

	// Split the stereo channels from the source output and the gain output
	// and merge them into the desired channels of the merger.
	source.connect(gainNode).connect(gainSplitter);
	source.connect(sourceSplitter);

	gainSplitter.connect(merger, 0, 0);
	gainSplitter.connect(merger, 1, 1);
	sourceSplitter.connect(merger, 0, 2);
	sourceSplitter.connect(merger, 1, 3);

	source.start(time);
	}

	audit.define(
	{label: 'create context', description: 'Create context for test'},
	function(task, should) {
	// Create offline audio context.
	context = new OfflineAudioContext(
	4, sampleRate * lengthInSeconds, sampleRate);
	task.done();
	});

	audit.define(
	{label: 'test', description: 'GainNode functionality'},
	function(task, should) {
	let merger = new ChannelMergerNode(
	context, {numberOfInputs: context.destination.channelCount});
	merger.connect(context.destination);

	// Create a buffer for a short "note".
	sinWaveBuffer = createSinWaveBuffer(bufferDurationSeconds, 880.0);

	let startTimes = [];
	let gainValues = [];

	// Render 11 notes, starting at a gain of 1.0, decreasing in gain by
	// 0.1. The last note will be of gain 0.0, so shouldn't be
	// perceptible in the rendered output.
	for (let i = 0; i < numberOfNotes; ++i) {
	let time = i * noteSpacing;
	let gain = 1.0 - i / (numberOfNotes - 1);
	startTimes.push(time);
	gainValues.push(gain);
	playNote(time, gain, merger);
	}

	context.startRendering()
	.then(buffer => {
	let actual0 = buffer.getChannelData(0);
	let actual1 = buffer.getChannelData(1);
	let reference0 = buffer.getChannelData(2);
	let reference1 = buffer.getChannelData(3);

	// It's ok to a frame too long since the sine pulses are
	// followed by silence.
	let bufferDurationFrames =
	Math.ceil(bufferDurationSeconds * context.sampleRate);

	// Apply the gains to the reference signal.
	for (let k = 0; k < startTimes.length; ++k) {
	// It's ok to be a frame early because the sine pulses are
	// preceded by silence.
	let startFrame =
	Math.floor(startTimes[k] * context.sampleRate);
	let gain = gainValues[k];
	for (let n = 0; n < bufferDurationFrames; ++n) {
	reference0[startFrame + n] *= gain;
	reference1[startFrame + n] *= gain;
	}
	}

	// Verify the channels are clsoe to the reference.
	should(actual0, 'Left output from gain node')
	.beCloseToArray(
	reference0, {relativeThreshold: 1.1877e-7});
	should(actual1, 'Right output from gain node')
	.beCloseToArray(
	reference1, {relativeThreshold: 1.1877e-7});

	// Test the SNR too for both channels.
	let snr0 = 10 * Math.log10(computeSNR(actual0, reference0));
	let snr1 = 10 * Math.log10(computeSNR(actual1, reference1));
	should(snr0, 'Left SNR (in dB)')
	.beGreaterThanOrEqualTo(148.71);
	should(snr1, 'Right SNR (in dB)')
	.beGreaterThanOrEqualTo(148.71);
	})
	.then(() => task.done());
	;
	});

	audit.run();
	</script>
	</body>
	</html>