Sub-sample accurate start for ABSN

webaudio/resources/biquad-testing.js

@@ -5,15 +5,16 @@ let signal;
 let renderedBuffer;
 let renderedData;
 
-let sampleRate = 44100.0;
+// Use a power of two to eliminate round-off in converting frame to time
+let sampleRate = 32768;
 let pulseLengthFrames = .1 * sampleRate;
 
 // Maximum allowed error for the test to succeed.  Experimentally determined.
 let maxAllowedError = 5.9e-8;
 
-// This must be large enough so that the filtered result is
-// essentially zero.  See comments for createTestAndRun.
-let timeStep = .1;
+// This must be large enough so that the filtered result is essentially zero.
+// See comments for createTestAndRun.  This must be a whole number of frames.
+let timeStep = Math.ceil(.1 * sampleRate) / sampleRate;
 
 // Maximum number of filters we can process (mostly for setting the
 // render length correctly.)

webaudio/resources/distance-model-testing.js

@@ -1,10 +1,13 @@
-let sampleRate = 44100.0;
+// Use a power of two to eliminate round-off when converting frames to time and
+// vice versa.
+let sampleRate = 32768;
 
 // How many panner nodes to create for the test.
 let nodesToCreate = 100;
 
-// Time step when each panner node starts.
-let timeStep = 0.001;
+// Time step when each panner node starts.  Make sure it starts on a frame
+// boundary.
+let timeStep = Math.floor(0.001 * sampleRate) / sampleRate;
 
 // Make sure we render long enough to get all of our nodes.
 let renderLengthSeconds = timeStep * (nodesToCreate + 1);
@@ -134,7 +137,7 @@ function checkDistanceResult(renderedBuffer, model, should) {
   // The max allowed error between the actual gain and the expected
   // value.  This is determined experimentally.  Set to 0 to see
   // what the actual errors are.
-  let maxAllowedError = 3.3e-6;
+  let maxAllowedError = 2.2720e-6;
 
   let success = true;
 

webaudio/resources/note-grain-on-testing.js

@@ -1,17 +1,23 @@
-let sampleRate = 44100.0;
+// Use a power of two to eliminate round-off converting from frames to time.
+let sampleRate = 32768;
 
 // How many grains to play.
 let numberOfTests = 100;
 
-// Duration of each grain to be played
-let duration = 0.01;
+// Duration of each grain to be played.  Make a whole number of frames
+let duration = Math.floor(0.01 * sampleRate) / sampleRate;
+
+// A little extra bit of silence between grain boundaries.  Must be a whole
+// number of frames.
+let grainGap = Math.floor(0.005 * sampleRate) / sampleRate;
 
 // Time step between the start of each grain.  We need to add a little
 // bit of silence so we can detect grain boundaries
-let timeStep = duration + .005;
+let timeStep = duration + grainGap;
 
-// Time step between the start for each grain.
-let grainOffsetStep = 0.001;
+// Time step between the start for each grain.  Must be a whole number of
+// frames.
+let grainOffsetStep = Math.floor(0.001 * sampleRate) / sampleRate;
 
 // How long to render to cover all of the grains.
 let renderTime = (numberOfTests + 1) * timeStep;

webaudio/resources/panner-model-testing.js

@@ -1,9 +1,12 @@
-let sampleRate = 44100.0;
+// Use a power of two to eliminate round-off when converting frames to time and
+// vice versa.
+let sampleRate = 32768;
 
 let numberOfChannels = 1;
 
-// Time step when each panner node starts.
-let timeStep = 0.001;
+// Time step when each panner node starts.  Make sure it starts on a frame
+// boundary.
+let timeStep = Math.floor(0.001 * sampleRate) / sampleRate;
 
 // Length of the impulse signal.
 let pulseLengthFrames = Math.round(timeStep * sampleRate);
@@ -114,7 +117,7 @@ function checkResult(renderedBuffer, should) {
   // The max error we allow between the rendered impulse and the
   // expected value.  This value is experimentally determined.  Set
   // to 0 to make the test fail to see what the actual error is.
-  let maxAllowedError = 1.3e-6;
+  let maxAllowedError = 1.1597e-6;
 
   let success = true;
 

webaudio/resources/stereopanner-testing.js

@@ -3,10 +3,12 @@ let StereoPannerTest = (function() {
   // Constants
   let PI_OVER_TWO = Math.PI * 0.5;
 
-  let gSampleRate = 44100;
+  // Use a power of two to eliminate any round-off when converting frames to
+  // time.
+  let gSampleRate = 32768;
 
-  // Time step when each panner node starts.
-  let gTimeStep = 0.001;
+  // Time step when each panner node starts.  Make sure this is on a frame boundary.
+  let gTimeStep = Math.floor(0.001 * gSampleRate) / gSampleRate;
 
   // How many panner nodes to create for the test
   let gNodesToCreate = 100;
@@ -77,7 +79,7 @@ let StereoPannerTest = (function() {
     // The max error we allow between the rendered impulse and the
     // expected value.  This value is experimentally determined.  Set
     // to 0 to make the test fail to see what the actual error is.
-    this.maxAllowedError = 1.3e-6;
+    this.maxAllowedError = 9.8015e-8;
 
     // Max (absolute) error and the index of the maxima for the left
     // and right channels.

webaudio/the-audio-api/the-audiobuffersourcenode-interface/audiobuffersource-playbackrate-zero.html

@@ -74,6 +74,42 @@
             .then(() => task.done());
       });
 
+      audit.define('subsample start with playback rate 0', (task, should) => {
+        let context = new OfflineAudioContext(1, renderLength, sampleRate);
+        let rampBuffer = new AudioBuffer(
+            {length: renderLength, sampleRate: context.sampleRate});
+        let data = new Float32Array(renderLength);
+        let startValue = 5;
+        for (let k = 0; k < data.length; ++k) {
+          data[k] = k + startValue;
+        }
+        rampBuffer.copyToChannel(data, 0);
+
+        let src = new AudioBufferSourceNode(
+            context, {buffer: rampBuffer, playbackRate: 0});
+
+        src.connect(context.destination);
+
+        // Purposely start the source between frame boundaries
+        let startFrame = 27.3;
+        src.start(startFrame / context.sampleRate);
+
+        context.startRendering()
+            .then(audioBuffer => {
+              let actualStartFrame = Math.ceil(startFrame);
+              let audio = audioBuffer.getChannelData(0);
+
+              should(
+                  audio.slice(0, actualStartFrame),
+                  `output[0:${actualStartFrame - 1}]`)
+                  .beConstantValueOf(0);
+              should(
+                  audio.slice(actualStartFrame), `output[${actualStartFrame}:]`)
+                  .beConstantValueOf(startValue);
+            })
+            .then(() => task.done());
+      });
+
       audit.run();
     </script>
   </body>