86 lines
1.9 KiB
JavaScript
86 lines
1.9 KiB
JavaScript
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var util = require( 'util' );
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var Transform = require( 'stream' ).Transform;
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var ogg_packet = require( 'ogg-packet' );
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var OpusEncoder = require( './OpusEncoder' );
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var Decoder = function( rate, channels, frameSize ) {
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Transform.call( this, { writableObjectMode: true } );
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this.rate = rate || 48000;
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this.channels = channels || 1;
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this.frameSize = frameSize || this.rate * 0.04;
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this.encoder = null;
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this.header = {};
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this.tags = null;
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this.pos = 0;
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this.samplesWritten = 0;
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this.packetBuffer = [];
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};
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util.inherits( Decoder, Transform );
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/**
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* Transform stream callback
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*/
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Decoder.prototype._transform = function( packet, encoding, done ) {
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// Write the header if it hasn't been written yet
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if( !this.encoder ) {
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this._parseHeader( packet );
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} else if( !this.tags ) {
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// TODO: Not implemented
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// this._parseTags( packet );
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this.tags = {};
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} else {
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this._processInput( packet );
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}
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done();
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};
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Decoder.prototype._parseHeader = function( packet ) {
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var header = packet.packet;
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var signature = header.slice( 0, 8 );
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if( signature.toString( 'ascii' ) !== 'OpusHead' ) {
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return this.emit( 'error', 'Bad header' );
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}
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this.header.version = header.readUInt8( 8 );
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this.header.channels = header.readUInt8( 9 );
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this.header.preSkip = header.readUInt16LE( 10 );
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this.header.rate = header.readUInt32LE( 12 );
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this.header.gain = header.readUInt16LE( 16 );
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this.header.channelMap = header.readUInt8( 18 );
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this.emit( 'format', {
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channels: this.channels,
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sampleRate: this.rate,
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bitDepth: 16,
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float: false,
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signed: true,
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gain: this.header.gain,
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preSkip: this.header.preSkip,
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version: this.header.version
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});
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this.encoder = new OpusEncoder( this.rate, this.channels );
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};
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Decoder.prototype._processInput = function( packet ) {
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var frame = packet.packet;
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var pcm = this.encoder.decode( frame );
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this.push( pcm );
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};
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module.exports = Decoder;
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