Skip to content

added getSamples() to process samples directly #2

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
rvosa wants to merge 1 commit into
base: master
Choose a base branch
from
Open

added getSamples() to process samples directly #2

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
89 changes: 49 additions & 40 deletions wav.js
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@ NOTE: Does not auto-correct:

/**
* Constructor: Parse Format chunk of WAV files.
*
*
* Fires onloadend() function after successful load.
*
* @param {File|Blob|ArrayBuffer} RIFF formatted WAV file
Expand All @@ -37,7 +37,8 @@ function wav(file) {

// original File and loaded ArrayBuffer
this.file = file instanceof Blob ? file : undefined;
this.buffer = file instanceof ArrayBuffer ? file : undefined;;
this.buffer = file instanceof ArrayBuffer ? file : undefined;
this.data = undefined;

// format
this.chunkID = undefined; // must be RIFF
Expand Down Expand Up @@ -77,7 +78,7 @@ wav.prototype.peek = function () {
var headerBlob = this.sliceFile(0, 44);
reader.readAsArrayBuffer(headerBlob);

reader.onloadend = function() {
reader.onloadend = function() {
that.buffer = this.result;
that.parseArrayBuffer.apply(that);
};
Expand All @@ -92,37 +93,37 @@ wav.prototype.parseArrayBuffer = function () {
catch (e) {
this.readyState = this.UNSUPPORTED_FORMAT;
this.error = e;
}
}

// trigger onloadend callback if exists
if (this.onloadend) {
this.onloadend.apply(this);
}
};

/**
* Walk through RIFF and WAVE format chunk
* Based on https://ccrma.stanford.edu/courses/422/projects/WaveFormat/
* and http://www.sonicspot.com/guide/wavefiles.html
*/
wav.prototype.parseHeader = function () {

this.chunkID = this.readText(0, 4);
this.chunkSize = this.readDecimal(4, 4);
if (this.chunkID !== 'RIFF') throw 'NOT_SUPPORTED_FORMAT';

this.format = this.readText(8, 4);
if (this.format !== 'WAVE') throw 'NOT_SUPPORTED_FORMAT';
this.compression = this.readDecimal(20, 2);
this.numChannels = this.readDecimal(22, 2);
this.sampleRate = this.readDecimal(24, 4);

this.compression = this.readDecimal(20, 2);
this.numChannels = this.readDecimal(22, 2);
this.sampleRate = this.readDecimal(24, 4);

// == SampleRate * NumChannels * BitsPerSample/8
this.byteRate = this.readDecimal(28, 4);
this.byteRate = this.readDecimal(28, 4);

// == NumChannels * BitsPerSample/8
this.blockAlign = this.readDecimal(32, 2);
this.blockAlign = this.readDecimal(32, 2);

this.bitsPerSample = this.readDecimal(34, 2);
};
Expand All @@ -132,13 +133,14 @@ wav.prototype.parseHeader = function () {
*/
wav.prototype.parseData = function () {

var chunkType = this.readText(36, 4);
var chunkSize = this.readDecimal(40, 4);
var chunkType = this.readText(38, 4);
//var chunkSize = this.readDecimal(44, 4);

// only support files where data chunk is first (canonical format)
if (chunkType === 'data') {
this.dataLength = chunkSize;
//this.dataLength = chunkSize;
this.dataOffset = 44;
this.dataLength = this.file.size - this.dataOffset;
}
else {
// duration cant be calculated && slice will not work
Expand All @@ -154,23 +156,23 @@ wav.prototype.parseData = function () {
* @param {int} end Length of requested slice in seconds
*/
wav.prototype.slice = function (start, length, callback) {

var reader = new FileReader();
var that = this;

// use the byterate to calculate number of bytes per second
var start = this.dataOffset + (start * this.byteRate);
var end = start + (length * this.byteRate);

var headerBlob = this.sliceFile(0, 44);
var dataBlob = this.sliceFile(start, end);

// concant header and data slice
var blob = new Blob([headerBlob, dataBlob]);

reader.readAsArrayBuffer(blob);
reader.onloadend = function() {
reader.onloadend = function() {

// update chunkSize in header
var chunkSize = new Uint8Array(this.result, 4, 4);
that.tolittleEndianDecBytes(chunkSize, 36+dataBlob.size);
Expand All @@ -183,18 +185,25 @@ wav.prototype.slice = function (start, length, callback) {
};
};

/*
* do we need direct access to samples?
*
wav.prototype.getSamples = function () {

// TODO load data chunk into buffer
if (this.bitsPerSample === 8)
this.dataSamples = new Uint8Array(this.buffer, 44, chunkSize/this.blockAlign);
else if (this.bitsPerSample === 16)
this.dataSamples = new Int16Array(this.buffer, 44, chunkSize/this.blockAlign);
/**
* Populates a TypedArray subclass with samples that is processed
* by the handler
*/
wav.prototype.getSamples = function (handler) {
var reader = new FileReader();
var that = this;
var dataBlob = this.sliceFile(this.dataOffset, this.dataLength + this.dataOffset);
reader.readAsArrayBuffer(dataBlob);
reader.onloadend = function() {
if (that.bitsPerSample === 8) {
handler(new Uint8Array(this.result));
}
else if (that.bitsPerSample === 16) {
handler(new Int16Array(this.result));
}
};
}
*/
//*/

/**
* Reads slice from buffer as String
Expand Down Expand Up @@ -242,19 +251,19 @@ wav.prototype.tolittleEndianDecBytes = function (a, decimalVal) {
* Slice the File using either standard slice or webkitSlice
*/
wav.prototype.sliceFile = function (start, end) {
if (this.file.slice) return this.file.slice(start, end);
if (this.file.slice) return this.file.slice(start, end);
if (this.file.webkitSlice) return this.file.webkitSlice(start, end);
};


wav.prototype.isCompressed = function () {
return this.compression !== 1;
return this.compression !== 1;
};

wav.prototype.isMono = function () {
return this.numChannels === 1;
return this.numChannels === 1;
};

wav.prototype.isStereo = function () {
return this.numChannels === 2;
};
Expand Down