File size: 2,066 Bytes
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var downloadBuffer = function(buffer) {
return window.URL.createObjectURL(bufferToWave(buffer.audioBuffers));
};
// Convert an AudioBuffer to a Blob using WAVE representation
function bufferToWave(audioBuffers) {
var audioBuffer = audioBuffers[0];
var numOfChan = audioBuffer.numberOfChannels;
var length = audioBuffer.length * numOfChan * 2 + 44;
var buffer = new ArrayBuffer(length);
var view = new DataView(buffer);
var channels = [];
var i;
var sample;
var offset = 0;
var pos = 0;
// write WAVE header
setUint32(0x46464952); // "RIFF"
setUint32(length - 8); // file length - 8
setUint32(0x45564157); // "WAVE"
setUint32(0x20746d66); // "fmt " chunk
setUint32(16); // length = 16
setUint16(1); // PCM (uncompressed)
setUint16(numOfChan);
setUint32(audioBuffer.sampleRate);
setUint32(audioBuffer.sampleRate * 2 * numOfChan); // avg. bytes/sec
setUint16(numOfChan * 2); // block-align
setUint16(16); // 16-bit (hardcoded in this demo)
setUint32(0x61746164); // "data" - chunk
setUint32(length - pos - 4); // chunk length
// write interleaved data
for(i = 0; i < numOfChan; i++)
channels.push(audioBuffer.getChannelData(i));
while(pos < length) {
for(i = 0; i < channels.length; i++) { // interleave channels
sample = Math.max(-1, Math.min(1, channels[i][offset])); // clamp
sample = (0.5 + sample < 0 ? sample * 32768 : sample * 32767)|0; // scale to 16-bit signed int
view.setInt16(pos, sample, true); // write 16-bit sample
pos += 2;
}
offset++; // next source sample
}
// create Blob
return new Blob([buffer], {type: "audio/wav"});
function setUint16(data) {
view.setUint16(pos, data, true);
pos += 2;
}
function setUint32(data) {
view.setUint32(pos, data, true);
pos += 4;
}
}
module.exports = downloadBuffer;
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