Modules

node_modules/node-opus/lib/Decoder.js

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

node_modules/node-opus/lib/Encoder.js

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+
+var util = require( 'util' );
+var Transform = require( 'stream' ).Transform;
+var ogg_packet = require( 'ogg-packet' );
+var OpusEncoder = require( './OpusEncoder' );
+
+// These are the valid rates for libopus according to
+// https://www.opus-codec.org/docs/opus_api-1.1.2/group__opus__encoder.html#gaa89264fd93c9da70362a0c9b96b9ca88
+var VALID_RATES = [ 8000, 12000, 16000, 24000, 48000 ];
+
+var Encoder = function( rate, channels, frameSize ) {
+    Transform.call( this, { readableObjectMode: true } );
+
+    this.rate = rate || 48000;
+
+    // Ensure the range is valid.
+    if( VALID_RATES.indexOf( this.rate ) === -1 ) {
+        throw new RangeError(
+                'Encoder rate (' + this.rate + ') is not valid. ' +
+                'Valid rates are: ' + VALID_RATES.join( ', ' ) );
+    }
+    
+    this.channels = channels || 1;
+    this.frameSize = frameSize || this.rate * 0.04;
+
+    this.encoder = new OpusEncoder( this.rate, this.channels );
+    this.frameOverflow = Buffer.alloc(0);
+
+    this.headerWritten = false;
+    this.pos = 0;
+    this.granulepos = 0;
+    this.samplesWritten = 0;
+};
+util.inherits( Encoder, Transform );
+
+/**
+ * Transform stream callback
+ */
+Encoder.prototype._transform = function( buf, encoding, done ) {
+
+	// Transform the buffer
+    this._processOutput( buf );
+
+    done();
+};
+
+Encoder.prototype._writeHeader = function() {
+
+	// OpusHead packet
+    var magicSignature = Buffer.from( 'OpusHead', 'ascii' );
+    var data = Buffer.from([
+        0x01,  // version
+        this.channels,
+        0x00, 0x0f,  // Preskip (default and recommended 3840)
+        ( ( this.rate & 0x000000ff ) >> 0 ),
+        ( ( this.rate & 0x0000ff00 ) >> 8 ),
+        ( ( this.rate & 0x00ff0000 ) >> 16 ),
+        ( ( this.rate & 0xff000000 ) >> 24 ),
+        0x00, 0x00,  // gain
+        0x00,  // Channel mappign (RTP, mono/stereo)
+    ]);
+
+    var header = Buffer.concat([ magicSignature, data ]);
+
+
+    var packet = new ogg_packet();
+    packet.packet = header;
+    packet.bytes = header.length;
+    packet.b_o_s = 1;
+    packet.e_o_s = 0;
+    packet.granulepos = -1;
+    packet.packetno = this.pos++;
+
+    this.push( packet );
+
+	// OpusTags packet
+    magicSignature = Buffer.from( 'OpusTags', 'ascii' );
+    var vendor = Buffer.from( 'node-opus', 'ascii' );
+    var vendorLength = Buffer.alloc( 4 );
+    vendorLength.writeUInt32LE( vendor.length, 0 );
+    var commentLength = Buffer.alloc( 4 );
+    commentLength.writeUInt32LE( 0, 0 );
+
+    header = Buffer.concat([
+        magicSignature, vendorLength, vendor, commentLength, Buffer.from([ 0xff ])
+    ]);
+
+    packet = new ogg_packet();
+    packet.packet = header;
+    packet.bytes = header.length;
+    packet.b_o_s = 0;
+    packet.e_o_s = 0;
+    packet.granulepos = -1;
+    packet.packetno = this.pos++;
+    packet.flush = true;
+
+    this.push( packet );
+
+    this.headerWritten = true;
+};
+
+Encoder.prototype._processOutput = function( buf ) {
+
+	// Calculate the total data available and data required for each frame.
+    var totalData = buf.length + this.frameOverflow.length;
+    var requiredData = this.frameSize * 2 * this.channels;
+
+	// Process output while we got enough for a frame.
+    while( totalData >= requiredData ) {
+
+		// If we got overflow, use it up first.
+        var buffer;
+        if( this.frameOverflow ) {
+
+            buffer = Buffer.concat([
+                this.frameOverflow,
+                buf.slice( 0, requiredData - this.frameOverflow.length )
+            ]);
+
+			// Cut the already used part off the buf.
+            buf = buf.slice( requiredData - this.frameOverflow.length );
+
+			// Remove overflow. We'll set it later so it'll never be null
+			// outside of this function.
+            this.frameOverflow = null;
+
+        } else {
+
+			// We got no overflow.
+			// Just cut the required bits from the buffer
+            buffer = buf.slice( 0, requiredData );
+            buf = buf.slice( requiredData );
+        }
+
+		// Flush frame and remove bits from the total data counter before
+		// repeating loop.
+        this._flushFrame( buffer );
+        totalData -= requiredData;
+    }
+
+	// Store the remainign buffer in the overflow.
+    this.frameOverflow = buf;
+};
+
+Encoder.prototype._flushFrame = function( frame, end ) {
+    var encoded = this.encoder.encode( frame );
+    this._pushEncodedBuffer(encoded, end);
+};
+
+Encoder.prototype._pushEncodedBuffer = function( encoded, end ) {
+    // Write the header if it hasn't been written yet
+    if( !this.headerWritten ) {
+        this._writeHeader();
+    }
+  
+    if( this.lastPacket ) {
+        this.push( this.lastPacket );
+    }
+
+    // Scale the frame size into 48 kHz bitrate, which is used for the
+    // granule positioning. We'll still update the samplesWritten just to
+    // ensure backwards compatibility.
+    this.granulepos += this.frameSize / this.rate * 48000;
+    this.samplesWritten += this.frameSize;
+
+    var packet = new ogg_packet();
+    packet.packet = encoded;
+    packet.bytes = encoded.length,
+    packet.b_o_s = 0;
+    packet.e_o_s = 0;
+    packet.granulepos = this.granulepos;
+    packet.packetno = this.pos++;
+    packet.flush = true;
+
+    this.lastPacket = packet;
+};
+
+Encoder.prototype._flush = function( done ) {
+
+    if( this.lastPacket ) {
+        this.lastPacket.e_o_s = 1;
+        this.push( this.lastPacket );
+    }
+
+    done();
+};
+
+module.exports = Encoder;

node_modules/node-opus/lib/OpusEncoder.js

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+
+"use strict";
+
+var binding = require('bindings')('node-opus');
+module.exports = binding.OpusEncoder;