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//This file is part of the XAudioJS library.
var XAudioJSResampledBuffer = [];
var XAudioJSOutputBuffer = [];
var XAudioJSResampleBufferStart = 0;
var XAudioJSResampleBufferEnd = 0;
var XAudioJSResampleBufferSize = 0;
var XAudioJSChannelsAllocated = 1;
//Message Receiver:
self.onmessage = function (event) {
var data = event.data;
switch (data[0]) {
case 0:
//Add new audio samples to our ring buffer:
var resampledResult = data[1];
var length = resampledResult.length;
for (var i = 0; i < length; ++i) {
XAudioJSResampledBuffer[XAudioJSResampleBufferEnd++] = resampledResult[i];
if (XAudioJSResampleBufferEnd == XAudioJSResampleBufferSize) {
XAudioJSResampleBufferEnd = 0;
}
if (XAudioJSResampleBufferStart == XAudioJSResampleBufferEnd) {
XAudioJSResampleBufferStart += XAudioJSChannelsAllocated;
if (XAudioJSResampleBufferStart == XAudioJSResampleBufferSize) {
XAudioJSResampleBufferStart = 0;
}
}
}
break;
case 1:
//Initialize:
XAudioJSResampleBufferSize = data[1];
XAudioJSChannelsAllocated = data[2];
XAudioJSResampledBuffer = new Float32Array(XAudioJSResampleBufferSize);
}
}
//MediaStream Polyfill Event:
self.onprocessmedia = function (event) {
//Get some buffer length computations:
var apiBufferLength = event.audioLength;
var apiBufferLengthAll = apiBufferLength * event.audioChannels;
if (apiBufferLengthAll > XAudioJSOutputBuffer.length) {
XAudioJSOutputBuffer = new Float32Array(apiBufferLengthAll);
}
//De-interleave the buffered audio while looping through our ring buffer:
var sampleFramesCount = Math.min(apiBufferLength, XAudioJSResampledSamplesLeft() / XAudioJSChannelsAllocated);
for (var sampleFramePosition = 0, channelOffset = 0; sampleFramePosition < sampleFramesCount; ++sampleFramePosition) {
for (channelOffset = sampleFramePosition; channelOffset < apiBufferLengthAll; channelOffset += apiBufferLength) {
XAudioJSOutputBuffer[channelOffset] = XAudioJSResampledBuffer[XAudioJSResampleBufferStart++];
if (XAudioJSResampleBufferStart == XAudioJSResampleBufferSize) {
XAudioJSResampleBufferStart = 0;
}
}
}
//Add some zero fill if we underran the required buffer fill amount:
while (sampleFramePosition < apiBufferLength) {
for (channelOffset = sampleFramePosition++; channelOffset < apiBufferLengthAll; channelOffset += apiBufferLength) {
XAudioJSOutputBuffer[channelOffset] = 0;
}
}
//Write some buffered audio:
event.writeAudio(XAudioJSOutputBuffer.subarray(0, apiBufferLengthAll));
//Request a buffer from the main thread:
self.postMessage(event.audioLength);
}
//Accessory function used to determine remaining samples in the ring buffer:
function XAudioJSResampledSamplesLeft() {
return ((XAudioJSResampleBufferStart <= XAudioJSResampleBufferEnd) ? 0 : XAudioJSResampleBufferSize) + XAudioJSResampleBufferEnd - XAudioJSResampleBufferStart;
}
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