scratchfoundation/scratch-audio
1
0
Fork 0
mirror of https://github.com/scratchfoundation/scratch-audio.git synced 2024-12-22 14:02:29 -05:00
Code Issues Projects Releases Packages Wiki Activity Actions

Rename to ADPCMSoundDecoder, and only decode

Browse source 
Scratch Storage now handles asset loading, so this class is now just the decoder
This commit is contained in:
Eric Rosenbaum 2017-03-22 18:08:44 -04:00
parent 4eb12ea075
commit c5daccef7c
2 changed files with 45 additions and 57 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

100
src/ADPCMSoundLoader.js → src/ADPCMSoundDecoder.js
View file

@ -3,78 +3,66 @@ var Tone = require('tone');
var log = require('./log');
/**
* Load wav audio files that have been compressed with the ADPCM format.
* Decode wav audio files that have been compressed with the ADPCM format.
* This is necessary because, while web browsers have native decoders for many audio
* formats, ADPCM is a non-standard format used by Scratch since its early days.
* This decoder is based on code from Scratch-Flash:
* https://github.com/LLK/scratch-flash/blob/master/src/sound/WAVFile.as
* @constructor
*/
function ADPCMSoundLoader () {
function ADPCMSoundDecoder () {
}
/**
* Load an ADPCM sound file from a URL, decode it, and return a promise
* with the audio buffer.
* @param {string} url - a url pointing to the ADPCM wav file
* Decode an ADPCM sound stored in an ArrayBuffer and return a promise
* with the decoded audio buffer.
* @param {ArrayBuffer} audioData - containing ADPCM encoded wav audio
* @return {Tone.Buffer}
*/
ADPCMSoundLoader.prototype.load = function (url) {
ADPCMSoundDecoder.prototype.decode = function (audioData) {
return new Promise(function (resolve, reject) {
var stream = new ArrayBufferStream(audioData);
var request = new XMLHttpRequest();
request.open('GET', url, true);
request.responseType = 'arraybuffer';
var riffStr = stream.readUint8String(4);
if (riffStr != 'RIFF') {
log.warn('incorrect adpcm wav header');
reject();
}
request.onload = function () {
var audioData = request.response;
var stream = new ArrayBufferStream(audioData);
var lengthInHeader = stream.readInt32();
if ((lengthInHeader + 8) != audioData.byteLength) {
log.warn('adpcm wav length in header: ' + lengthInHeader + ' is incorrect');
}
var riffStr = stream.readUint8String(4);
if (riffStr != 'RIFF') {
log.warn('incorrect adpcm wav header');
reject();
}
var wavStr = stream.readUint8String(4);
if (wavStr != 'WAVE') {
log.warn('incorrect adpcm wav header');
reject();
}
var lengthInHeader = stream.readInt32();
if ((lengthInHeader + 8) != audioData.byteLength) {
log.warn('adpcm wav length in header: ' + lengthInHeader + ' is incorrect');
}
var formatChunk = this.extractChunk('fmt ', stream);
this.encoding = formatChunk.readUint16();
this.channels = formatChunk.readUint16();
this.samplesPerSecond = formatChunk.readUint32();
this.bytesPerSecond = formatChunk.readUint32();
this.blockAlignment = formatChunk.readUint16();
this.bitsPerSample = formatChunk.readUint16();
formatChunk.position += 2; // skip extra header byte count
this.samplesPerBlock = formatChunk.readUint16();
this.adpcmBlockSize = ((this.samplesPerBlock - 1) / 2) + 4; // block size in bytes
var wavStr = stream.readUint8String(4);
if (wavStr != 'WAVE') {
log.warn('incorrect adpcm wav header');
reject();
}
var samples = this.imaDecompress(this.extractChunk('data', stream), this.adpcmBlockSize);
var formatChunk = this.extractChunk('fmt ', stream);
this.encoding = formatChunk.readUint16();
this.channels = formatChunk.readUint16();
this.samplesPerSecond = formatChunk.readUint32();
this.bytesPerSecond = formatChunk.readUint32();
this.blockAlignment = formatChunk.readUint16();
this.bitsPerSample = formatChunk.readUint16();
formatChunk.position += 2; // skip extra header byte count
this.samplesPerBlock = formatChunk.readUint16();
this.adpcmBlockSize = ((this.samplesPerBlock - 1) / 2) + 4; // block size in bytes
// todo: this line is the only place Tone is used here, should be possible to remove
var buffer = Tone.context.createBuffer(1, samples.length, this.samplesPerSecond);
var samples = this.imaDecompress(this.extractChunk('data', stream), this.adpcmBlockSize);
// todo: this line is the only place Tone is used here, should be possible to remove
var buffer = Tone.context.createBuffer(1, samples.length, this.samplesPerSecond);
// todo: optimize this? e.g. replace the divide by storing 1/32768 and multiply?
for (var i=0; i<samples.length; i++) {
buffer.getChannelData(0)[i] = samples[i] / 32768;
}
resolve(buffer);
}.bind(this);
request.send();
// todo: optimize this? e.g. replace the divide by storing 1/32768 and multiply?
for (var i=0; i<samples.length; i++) {
buffer.getChannelData(0)[i] = samples[i] / 32768;
}
resolve(buffer);
}.bind(this));
};
@ -82,7 +70,7 @@ ADPCMSoundLoader.prototype.load = function (url) {
* Data used by the decompression algorithm
* @type {Array}
*/
ADPCMSoundLoader.prototype.stepTable = [
ADPCMSoundDecoder.prototype.stepTable = [
7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 19, 21, 23, 25, 28, 31, 34, 37, 41, 45,
50, 55, 60, 66, 73, 80, 88, 97, 107, 118, 130, 143, 157, 173, 190, 209, 230,
253, 279, 307, 337, 371, 408, 449, 494, 544, 598, 658, 724, 796, 876, 963,
@ -94,7 +82,7 @@ ADPCMSoundLoader.prototype.stepTable = [
* Data used by the decompression algorithm
* @type {Array}
*/
ADPCMSoundLoader.prototype.indexTable = [
ADPCMSoundDecoder.prototype.indexTable = [
-1, -1, -1, -1, 2, 4, 6, 8,
-1, -1, -1, -1, 2, 4, 6, 8];
@ -104,7 +92,7 @@ ADPCMSoundLoader.prototype.indexTable = [
* @param {ArrayBufferStream} stream - an stream containing the audio data
* @return {ArrayBufferStream} a stream containing the desired chunk
*/
ADPCMSoundLoader.prototype.extractChunk = function (chunkType, stream) {
ADPCMSoundDecoder.prototype.extractChunk = function (chunkType, stream) {
stream.position = 12;
while (stream.position < (stream.getLength() - 8)) {
var typeStr = stream.readUint8String(4);
@ -125,7 +113,7 @@ ADPCMSoundLoader.prototype.extractChunk = function (chunkType, stream) {
* @param {number} blockSize - the number of bytes in the stream
* @return {Int16Array} the uncompressed audio samples
*/
ADPCMSoundLoader.prototype.imaDecompress = function (compressedData, blockSize) {
ADPCMSoundDecoder.prototype.imaDecompress = function (compressedData, blockSize) {
var sample, step, code, delta;
var index = 0;
var lastByte = -1; // -1 indicates that there is no saved lastByte
@ -175,4 +163,4 @@ ADPCMSoundLoader.prototype.imaDecompress = function (compressedData, blockSize)
return samples;
};
module.exports = ADPCMSoundLoader;
module.exports = ADPCMSoundDecoder;

2
src/index.js
View file

@ -10,7 +10,7 @@ var EchoEffect = require('./effects/EchoEffect');
var ReverbEffect = require('./effects/ReverbEffect');
var SoundPlayer = require('./SoundPlayer');
var ADPCMSoundLoader = require('./ADPCMSoundLoader');
var ADPCMSoundDecoder = require('./ADPCMSoundDecoder');
var InstrumentPlayer = require('./InstrumentPlayer');
var DrumPlayer = require('./DrumPlayer');