Complete the implementation of up/down-mixing rules for AudioNode

third_party/WebKit/LayoutTests/webaudio/resources/mixing-rules.js

+// Utilities for mixing rule testing.
+// http://webaudio.github.io/web-audio-api/#channel-up-mixing-and-down-mixing
+
+
+/**
+ * Create an n-channel buffer, with all sample data zero except for a shifted
+ * impulse. The impulse position depends on the channel index. For example, for
+ * a 4-channel buffer:
+ *  channel 0: 1 0 0 0 0 0 0 0
+ *  channel 1: 0 1 0 0 0 0 0 0
+ *  channel 2: 0 0 1 0 0 0 0 0
+ *  channel 3: 0 0 0 1 0 0 0 0
+ * @param  {AudioContext} context     Associated AudioContext.
+ * @param  {Number} numberOfChannels  Number of channels of test buffer.
+ * @param  {Number} frameLength       Buffer length in frames.
+ * @return {AudioBuffer}
+ */
+function createShiftedImpulseBuffer(context, numberOfChannels, frameLength) {
+    var shiftedImpulseBuffer = context.createBuffer(numberOfChannels, frameLength, context.sampleRate);
+    for (var channel = 0; channel < numberOfChannels; ++channel) {
+      var data = shiftedImpulseBuffer.getChannelData(channel);
+      data[channel] = 1;
+    }
+
+    return shiftedImpulseBuffer;
+}
+
+/**
+ * Create a string displays the content of AudioBuffer.

[Raymond Toy, 2016/03/09 22:14:19]

"string displays" -> "string that displays"

[hongchan, 2016/03/09 23:26:11]

Done.

+ * @param  {AudioBuffer} audioBuffer  AudioBuffer object to stringify.
+ * @param  {Number} frameLength       Number of frames to be printed.
+ * @param  {Number} frameOffset       Starting frame position for printing.
+ * @return {String}
+ */
+function stringifyBuffer(audioBuffer, frameLength, frameOffset) {
+  frameOffset = (frameOffset || 0);
+
+  var stringifiedBuffer = '';
+  for (var channel = 0; channel < audioBuffer.numberOfChannels; ++channel) {
+    var channelData = audioBuffer.getChannelData(channel);
+    for (var i = 0; i < frameLength; ++i)
+      stringifiedBuffer += channelData[i + frameOffset] + ' ';
+    stringifiedBuffer += '\n';
+  }
+
+  return stringifiedBuffer;
+}
+
+/**
+ * Compute number of channels from the connection.
+ * @param  {String} connections         A string specifies the connection. For
+ *                                      example, the string "128" means 3
+ *                                      connections, having 1, 2, and 8 channels
+ *                                      respectively.
+ * @param  {Number} channelCount        Channel count.
+ * @param  {String} channelCountMode    Channel count mode.
+ * @return {Number}                     Computed number of channels.
+ */
+function computeNumberOfChannels(connections, channelCount, channelCountMode) {
+  if (channelCountMode == "explicit")
+    return channelCount;
+
+  // Must have at least one channel.
+  var computedNumberOfChannels = 1;
+
+  // Compute "computedNumberOfChannels" based on all the connections.
+  for (var i = 0; i < connections.length; ++i) {
+    var connectionNumberOfChannels = parseInt(connections[i]);
+    computedNumberOfChannels = Math.max(computedNumberOfChannels, connectionNumberOfChannels);
+  }
+
+  if (channelCountMode == "clamped-max")
+    computedNumberOfChannels = Math.min(computedNumberOfChannels, channelCount);
+
+  return computedNumberOfChannels;
+}
+
+/**
+ * Apply up/down-mixing (in-place summing) based on 'speaker' interpretation.
+ * @param  {AudioBuffer} input          Input audio buffer.
+ * @param  {AudioBuffer} output         Output audio buffer.
+ */
+function speakersSum(input, output) {
+  if (input.length != output.length) {
+    throw '[mixing-rules.js] speakerSum(): buffer lengths mismatch (input: '
+      + input.length + ', output: ' + output.length + ')';
+  }
+
+  if (input.numberOfChannels === output.numberOfChannels) {
+    for (var channel = 0; channel < output.numberOfChannels; ++channel) {
+      var inputChannel = input.getChannelData(channel);
+      var outputChannel = output.getChannelData(channel);
+      for (var i = 0; i < outputChannel.length; i++)
+        outputChannel[i] += inputChannel[i];
+    }
+  } else if (input.numberOfChannels < output.numberOfChannels) {
+    processUpMix(input, output);
+  } else {
+    processDownMix(input, output);
+  }
+}
+
+/**
+ * In-place summing to |output| based on 'discrete' channel interpretation.
+ * @param  {AudioBuffer} input          Input audio buffer.
+ * @param  {AudioBuffer} output         Output audio buffer.
+ */
+function discreteSum(input, output) {
+  if (input.length != output.length) {
+    throw '[mixing-rules.js] speakerSum(): buffer lengths mismatch (input: '
+      + input.length + ', output: ' + output.length + ')';
+  }
+
+  var numberOfChannels = Math.min(input.numberOfChannels, output.numberOfChannels)
+
+  for (var channel = 0; channel < numberOfChannels; ++channel) {
+    var inputChannel = input.getChannelData(channel);
+    var outputChannel = output.getChannelData(channel);
+    for (var i = 0; i < outputChannel.length; i++)
+      outputChannel[i] += inputChannel[i];
+  }
+}
+
+/**
+ * Perform up-mix by in-place summing to |output| buffer.

[Raymond Toy, 2016/03/09 22:14:19]

For consistency, you probably want to add this comment to the following
functions to emphasize in-place summing operation to the output.

[hongchan, 2016/03/09 23:26:11]

Done.

+ * @param  {AudioBuffer} input          Input audio buffer.
+ * @param  {AudioBuffer} output         Output audio buffer.
+ */
+function processUpMix(input, output) {
+  var numberOfInputChannels = input.numberOfChannels;
+  var numberOfOutputChannels = output.numberOfChannels;
+  var i, length = output.length;
+
+  // Up-mixing: 1 -> 2, 1 -> 4
+  //   output.L += input
+  //   output.R += input
+  //   output.SL += 0 (in the case of 1 -> 4)
+  //   output.SR += 0 (in the case of 1 -> 4)
+  if ((numberOfInputChannels === 1 && numberOfOutputChannels === 2) ||
+      (numberOfInputChannels === 1 && numberOfOutputChannels === 4)) {
+    var inputChannel = input.getChannelData(0);
+    var outputChannel0 = output.getChannelData(0);
+    var outputChannel1 = output.getChannelData(1);
+    for (i = 0; i < length; i++) {
+      outputChannel0[i] += inputChannel[i];
+      outputChannel1[i] += inputChannel[i];
+    }
+
+    return;
+  }
+
+  // Up-mixing: 1 -> 5.1
+  //   output.L += 0
+  //   output.R += 0
+  //   output.C += input
+  //   output.LFE += 0
+  //   output.SL += 0
+  //   output.SR += 0
+  if (numberOfInputChannels == 1 && numberOfOutputChannels == 6) {
+    var inputChannel = input.getChannelData(0);
+    var outputChannel2 = output.getChannelData(2);
+    for (i = 0; i < length; i++)
+      outputChannel2[i] += inputChannel[i];
+
+    return;
+  }
+
+  // Up-mixing: 2 -> 4, 2 -> 5.1
+  //   output.L += input.L
+  //   output.R += input.R
+  //   output.C += 0 (in the case of 2 -> 5.1)
+  //   output.LFE += 0 (in the case of 2 -> 5.1)
+  //   output.SL += 0
+  //   output.SR += 0
+  if ((numberOfInputChannels === 2 && numberOfOutputChannels === 4) ||
+      (numberOfInputChannels === 2 && numberOfOutputChannels === 6)) {
+    var inputChannel0 = input.getChannelData(0);
+    var inputChannel1 = input.getChannelData(1);
+    var outputChannel0 = output.getChannelData(0);
+    var outputChannel1 = output.getChannelData(1);
+    for (i = 0; i < length; i++) {
+      outputChannel0[i] += inputChannel0[i];
+      outputChannel1[i] += inputChannel1[i];
+    }
+
+    return;
+  }
+
+  // Up-mixing: 4 -> 5.1
+  //   output.L += input.L
+  //   output.R += input.R
+  //   output.C += 0
+  //   output.LFE += 0
+  //   output.SL += input.SL
+  //   output.SR += input.SR
+  if (numberOfInputChannels === 4 && numberOfOutputChannels === 6) {
+    var inputChannel0 = input.getChannelData(0); // input.L
+    var inputChannel1 = input.getChannelData(1); // input.R
+    var inputChannel2 = input.getChannelData(2); // input.SL
+    var inputChannel3 = input.getChannelData(3); // input.SR
+    var outputChannel0 = output.getChannelData(0); // output.L
+    var outputChannel1 = output.getChannelData(1); // output.R
+    var outputChannel4 = output.getChannelData(4); // output.SL
+    var outputChannel5 = output.getChannelData(5); // output.SR
+    for (i = 0; i < length; i++) {
+      outputChannel0[i] += inputChannel0[i];
+      outputChannel1[i] += inputChannel1[i];
+      outputChannel4[i] += inputChannel2[i];
+      outputChannel5[i] += inputChannel3[i];
+    }
+
+    return;
+  }
+
+  // All other cases, fall back to the discrete sum.
+  discreteSum(input, output);
+}
+
+/**
+ * Process down-mix from source to destination by summing into the existing data.
+ * @param  {AudioBuffer} input          Input audio buffer.
+ * @param  {AudioBuffer} output         Output audio buffer.
+ */
+function processDownMix(input, output) {
+  var numberOfInputChannels = input.numberOfChannels;
+  var numberOfOutputChannels = output.numberOfChannels;
+  var i, length = output.length;
+
+  // Down-mixing: 2 -> 1
+  //   output += 0.5 * (input.L + input.R)
+  if (numberOfInputChannels === 2 && numberOfOutputChannels === 1) {
+    var inputChannel0 = input.getChannelData(0); // input.L
+    var inputChannel1 = input.getChannelData(1); // input.R
+    var outputChannel0 = output.getChannelData(0);
+    for (i = 0; i < length; i++)
+      outputChannel0[i] += 0.5 * (inputChannel0[i] + inputChannel1[i]);
+
+    return;
+  }
+
+  // Down-mixing: 4 -> 1
+  //   output += 0.25 * (input.L + input.R + input.SL + input.SR)
+  if (numberOfInputChannels === 4 && numberOfOutputChannels === 1) {
+    var inputChannel0 = input.getChannelData(0); // input.L
+    var inputChannel1 = input.getChannelData(1); // input.R
+    var inputChannel2 = input.getChannelData(2); // input.SL
+    var inputChannel3 = input.getChannelData(3); // input.SR
+    var outputChannel0 = output.getChannelData(0);
+    for (i = 0; i < length; i++) {
+      outputChannel0[i] += 0.25 * (inputChannel0[i] + inputChannel1[i]
+        + inputChannel2[i] + inputChannel3[i]);
+    }
+
+    return;
+  }
+
+  // Down-mixing: 5.1 -> 1
+  //   output += sqrt(1/2) * (input.L + input.R) + input.C
+  //            + 0.5 * (input.SL + input.SR)
+  if (numberOfInputChannels === 6 && numberOfOutputChannels === 1) {
+    var inputChannel0 = input.getChannelData(0); // input.L
+    var inputChannel1 = input.getChannelData(1); // input.R
+    var inputChannel2 = input.getChannelData(2); // input.C
+    var inputChannel4 = input.getChannelData(4); // input.SL
+    var inputChannel5 = input.getChannelData(5); // input.SR
+    var outputChannel0 = output.getChannelData(0);
+    var scaleSqrtHalf = Math.sqrt(0.5);
+    for (i = 0; i < length; i++) {
+      outputChannel0[i] +=
+        scaleSqrtHalf * (inputChannel0[i] + inputChannel1[i])
+        + inputChannel2[i] + 0.5 * (inputChannel4[i] + inputChannel5[i]);
+    }
+
+    return;
+  }
+
+  // Down-mixing: 4 -> 2
+  //   output.L += 0.5 * (input.L + input.SL)
+  //   output.R += 0.5 * (input.R + input.SR)
+  if (numberOfInputChannels == 4 && numberOfOutputChannels == 2) {
+    var inputChannel0 = input.getChannelData(0); // input.L
+    var inputChannel1 = input.getChannelData(1); // input.R
+    var inputChannel2 = input.getChannelData(2); // input.SL
+    var inputChannel3 = input.getChannelData(3); // input.SR
+    var outputChannel0 = output.getChannelData(0); // output.L
+    var outputChannel1 = output.getChannelData(1); // output.R
+    for (i = 0; i < length; i++) {
+      outputChannel0[i] += 0.5 * (inputChannel0[i] + inputChannel2[i]);
+      outputChannel1[i] += 0.5 * (inputChannel1[i] + inputChannel3[i]);
+    }
+
+    return;
+  }
+
+  // Down-mixing: 5.1 -> 2
+  //   output.L += input.L + sqrt(1/2) * (input.C + input.SL)
+  //   output.R += input.R + sqrt(1/2) * (input.C + input.SR)
+  if (numberOfInputChannels == 6 && numberOfOutputChannels == 2) {
+    var inputChannel0 = input.getChannelData(0); // input.L
+    var inputChannel1 = input.getChannelData(1); // input.R
+    var inputChannel2 = input.getChannelData(2); // input.C
+    var inputChannel4 = input.getChannelData(4); // input.SL
+    var inputChannel5 = input.getChannelData(5); // input.SR
+    var outputChannel0 = output.getChannelData(0); // output.L
+    var outputChannel1 = output.getChannelData(1); // output.R
+    var scaleSqrtHalf = Math.sqrt(0.5);
+    for (i = 0; i < length; i++) {
+      outputChannel0[i] += inputChannel0[i]
+        + scaleSqrtHalf * (inputChannel2[i] + inputChannel4[i]);
+      outputChannel1[i] += inputChannel1[i]
+        + scaleSqrtHalf * (inputChannel2[i] + inputChannel5[i]);
+    }
+
+    return;
+  }
+
+  // Down-mixing: 5.1 -> 4
+  //   output.L += input.L + sqrt(1/2) * input.C
+  //   output.R += input.R + sqrt(1/2) * input.C
+  //   output.SL += input.SL
+  //   output.SR += input.SR
+  if (numberOfInputChannels === 6 && numberOfOutputChannels === 4) {
+    var inputChannel0 = input.getChannelData(0); // input.L
+    var inputChannel1 = input.getChannelData(1); // input.R
+    var inputChannel2 = input.getChannelData(2); // input.C
+    var inputChannel4 = input.getChannelData(4); // input.SL
+    var inputChannel5 = input.getChannelData(5); // input.SR
+    var outputChannel0 = output.getChannelData(0); // output.L
+    var outputChannel1 = output.getChannelData(1); // output.R
+    var outputChannel2 = output.getChannelData(2); // output.SL
+    var outputChannel3 = output.getChannelData(3); // output.SR
+    var scaleSqrtHalf = Math.sqrt(0.5);
+    for (i = 0; i < length; i++) {
+      outputChannel0[i] += inputChannel0[i] + scaleSqrtHalf * inputChannel2[i];
+      outputChannel1[i] += inputChannel1[i] + scaleSqrtHalf * inputChannel2[i];
+      outputChannel2[i] += inputChannel4[i];
+      outputChannel3[i] += inputChannel5[i];
+    }
+
+    return;
+  }
+
+  // All other cases, fall back to the discrete sum.
+  discreteSum(input, output);
+}