third_party/WebKit/LayoutTests/webaudio/audioparam-setTargetAtTime-limit.html - chromium/src - Git at Google

 <!doctype html>
 <html>
   <head>
     <title>Test setTargetAtTime Approach to Limit</title>
     <script src="../resources/js-test.js"></script>
     <script src="resources/compatibility.js"></script>
     <script src="resources/audio-testing.js"></script>
     <script src="resources/audioparam-testing.js"></script>
   </head>

   <body>
     <script>
       description("Test setTargetAtTime Approach to Limit");
       window.jsTestIsAsync = true;

       var audit = Audit.createTaskRunner();

       audit.defineTask("approach 1", function(done) {
         var sampleRate = 48000;

         // A really short time constant so that setTargetAtTime approaches the limiting value well
         // before the end of the test.
         var timeConstant = 0.001;

         // Find the time where setTargetAtTime is close enough to the limit.  Since we're
         // approaching 1, use a value of eps smaller than kSetTargetThreshold (5e-7) in
         // AudioParamTimeline.cpp.  This is to account for round-off in the actual implementation
         // (which uses a filter and not the formula.)
         var limitThreshold = 1e-7;

         runTest({
             sampleRate: sampleRate,
             v0: 0,
             v1: 1,
             timeConstant: timeConstant,
             eps: limitThreshold,
             // Experimentally determined
             threshold: 2.4273e-7
         }).then(done);
       })

       audit.defineTask("approach 0", function(done) {
         // Use the equation for setTargetAtTime to figure out when we are close to 0:
         //
         //   v(t) = exp(-t/tau)
         //
         // So find t such that exp(-t/tau) <= eps.  Thus t >= - tau * log(eps).
         //
         // For eps, use 1e-20 (kSetTargetZeroThreshold in AudioParamTimeline.cpp).

         var sampleRate = 48000;

         // A really short time constant so that setTargetAtTime approaches the limiting value well
         // before the end of the test.
         var timeConstant = 0.001;

         // Find the time where setTargetAtTime is close enough to the limit.  Since we're
         // approaching 0, use a value of eps smaller than kSetTargetZeroThreshold (1e-20) in
         // AudioParamTimeline.cpp.  This is to account for round-off in the actual implementation
         // (which uses a filter and not the formula.)
         var limitThreshold = 1e-21;

         runTest({
             sampleRate: sampleRate,
             v0: 1,
             v1: 0,
             timeConstant: timeConstant,
             eps: limitThreshold,
             // Experimentally determined
             threshold: 4.7470e-8
         }).then(done);
       });

       function findLimitTime(v0, v1, timeConstant, eps) {
         // Find the time at which the setTargetAtTime is close enough to the target value |v1| where
         // we can consider the curve to have reached its limiting value.
         //
         // If v1 = 0, |eps| is the absolute error between the actual value and
         // |v1|.  Otherwise, |eps| is the relative error between the actual value and |v1|.
         //
         // The curve is
         //
         //   v(t) = v1 - (v1 - v0) * exp(-t/timeConstant)
         //
         // If v1 = 0,
         //
         //   v(t) = v0 * exp(-t/timeConstant)
         //
         // Solve this for when |v(t)| <= eps:
         //
         //   t >= timeConstant * log(v0/eps)
         //
         // For v1 not zero, we want |v(t) - v1|/|v1| <= eps:
         //
         //   t >= timeConstant * log(abs(v1-v0)/eps/v1)

         if (v1)
           return timeConstant * Math.log(Math.abs(v1-v0)/eps/v1);
         else
           return timeConstant * Math.log(v0/eps);
       }

       function runTest(options) {
         var renderLength = 1;

         var context = new OfflineAudioContext(1, renderLength * sampleRate, options.sampleRate);

         // A constant source
         var source = context.createBufferSource();
         source.buffer = createConstantBuffer(context, 1, 1);
         source.loop = true;

         var gain = context.createGain();
         gain.gain.setValueAtTime(options.v0, 0);
         gain.gain.setTargetAtTime(options.v1, 0, options.timeConstant);

         source.connect(gain);
         gain.connect(context.destination);

         source.start();

         return context.startRendering().then(function (resultBuffer) {
           var actual = resultBuffer.getChannelData(0);
           var expected = createExponentialApproachArray(0, renderLength,
             options.v0, options.v1,
             options.sampleRate, options.timeConstant);

           var message = "setTargetAtTime(" + options.v1 + ", 0, " + options.timeConstant + ")";

           // Determine where the tail of the curve begins.  (Where the curve has basically reached
           // the limit value.)
           var tailTime = findLimitTime(options.v0, options.v1, options.timeConstant, options.eps);
           var tailFrame = Math.ceil(tailTime * options.sampleRate);

           var success = true;
           success = Should("Initial output of " + tailFrame + " samples for " + message,
               actual.slice(0, tailFrame))
             .beCloseToArray(expected.slice(0, tailFrame), options.threshold) && success;

           success = Should("Tail output for " + message,
               actual.slice(tailFrame))
             .containValues([options.v1]) && success;

           if (success)
             testPassed(message + " had the expected values.\n");
           else
             testFailed(message + " did not have the expected values.\n");
         });
       }

       audit.defineTask("finish", function (done) {
         finishJSTest();
         done();
       });

       audit.runTasks();
     </script>
   </body>
 </html>
	<!doctype html>
	<html>
	<head>
	<title>Test setTargetAtTime Approach to Limit</title>
	<script src="../resources/js-test.js"></script>
	<script src="resources/compatibility.js"></script>
	<script src="resources/audio-testing.js"></script>
	<script src="resources/audioparam-testing.js"></script>
	</head>

	<body>
	<script>
	description("Test setTargetAtTime Approach to Limit");
	window.jsTestIsAsync = true;

	var audit = Audit.createTaskRunner();

	audit.defineTask("approach 1", function(done) {
	var sampleRate = 48000;

	// A really short time constant so that setTargetAtTime approaches the limiting value well
	// before the end of the test.
	var timeConstant = 0.001;

	// Find the time where setTargetAtTime is close enough to the limit. Since we're
	// approaching 1, use a value of eps smaller than kSetTargetThreshold (5e-7) in
	// AudioParamTimeline.cpp. This is to account for round-off in the actual implementation
	// (which uses a filter and not the formula.)
	var limitThreshold = 1e-7;

	runTest({
	sampleRate: sampleRate,
	v0: 0,
	v1: 1,
	timeConstant: timeConstant,
	eps: limitThreshold,
	// Experimentally determined
	threshold: 2.4273e-7
	}).then(done);
	})

	audit.defineTask("approach 0", function(done) {
	// Use the equation for setTargetAtTime to figure out when we are close to 0:
	//
	// v(t) = exp(-t/tau)
	//
	// So find t such that exp(-t/tau) <= eps. Thus t >= - tau * log(eps).
	//
	// For eps, use 1e-20 (kSetTargetZeroThreshold in AudioParamTimeline.cpp).

	var sampleRate = 48000;

	// A really short time constant so that setTargetAtTime approaches the limiting value well
	// before the end of the test.
	var timeConstant = 0.001;

	// Find the time where setTargetAtTime is close enough to the limit. Since we're
	// approaching 0, use a value of eps smaller than kSetTargetZeroThreshold (1e-20) in
	// AudioParamTimeline.cpp. This is to account for round-off in the actual implementation
	// (which uses a filter and not the formula.)
	var limitThreshold = 1e-21;

	runTest({
	sampleRate: sampleRate,
	v0: 1,
	v1: 0,
	timeConstant: timeConstant,
	eps: limitThreshold,
	// Experimentally determined
	threshold: 4.7470e-8
	}).then(done);
	});

	function findLimitTime(v0, v1, timeConstant, eps) {
	// Find the time at which the setTargetAtTime is close enough to the target value \|v1\| where
	// we can consider the curve to have reached its limiting value.
	//
	// If v1 = 0, \|eps\| is the absolute error between the actual value and
	// \|v1\|. Otherwise, \|eps\| is the relative error between the actual value and \|v1\|.
	//
	// The curve is
	//
	// v(t) = v1 - (v1 - v0) * exp(-t/timeConstant)
	//
	// If v1 = 0,
	//
	// v(t) = v0 * exp(-t/timeConstant)
	//
	// Solve this for when \|v(t)\| <= eps:
	//
	// t >= timeConstant * log(v0/eps)
	//
	// For v1 not zero, we want \|v(t) - v1\|/\|v1\| <= eps:
	//
	// t >= timeConstant * log(abs(v1-v0)/eps/v1)

	if (v1)
	return timeConstant * Math.log(Math.abs(v1-v0)/eps/v1);
	else
	return timeConstant * Math.log(v0/eps);
	}

	function runTest(options) {
	var renderLength = 1;

	var context = new OfflineAudioContext(1, renderLength * sampleRate, options.sampleRate);

	// A constant source
	var source = context.createBufferSource();
	source.buffer = createConstantBuffer(context, 1, 1);
	source.loop = true;

	var gain = context.createGain();
	gain.gain.setValueAtTime(options.v0, 0);
	gain.gain.setTargetAtTime(options.v1, 0, options.timeConstant);

	source.connect(gain);
	gain.connect(context.destination);

	source.start();

	return context.startRendering().then(function (resultBuffer) {
	var actual = resultBuffer.getChannelData(0);
	var expected = createExponentialApproachArray(0, renderLength,
	options.v0, options.v1,
	options.sampleRate, options.timeConstant);

	var message = "setTargetAtTime(" + options.v1 + ", 0, " + options.timeConstant + ")";

	// Determine where the tail of the curve begins. (Where the curve has basically reached
	// the limit value.)
	var tailTime = findLimitTime(options.v0, options.v1, options.timeConstant, options.eps);
	var tailFrame = Math.ceil(tailTime * options.sampleRate);

	var success = true;
	success = Should("Initial output of " + tailFrame + " samples for " + message,
	actual.slice(0, tailFrame))
	.beCloseToArray(expected.slice(0, tailFrame), options.threshold) && success;

	success = Should("Tail output for " + message,
	actual.slice(tailFrame))
	.containValues([options.v1]) && success;

	if (success)
	testPassed(message + " had the expected values.\n");
	else
	testFailed(message + " did not have the expected values.\n");
	});
	}

	audit.defineTask("finish", function (done) {
	finishJSTest();
	done();
	});

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