rtp/audio processing (pcm broken)

Author: stephen

.gitignore

@@ -8,6 +8,7 @@ lcov.info
 *.pid
 *.gz
 *.pcap
+*.pcm
 
 pids
 logs

lib/audioprocessor.js

@@ -0,0 +1,18 @@
+var Speaker = require('speaker');
+
+var audioProcessor = function(rtspServer) {
+	var self = this;
+
+	var speaker = new Speaker({
+	  channels: 2,          // 2 channels
+	  bitDepth: 16,         // 16-bit samples
+	  sampleRate: 44100    // 44,100 Hz sample rate
+	});
+
+	self.process = function(bytes) {
+		speaker.write(bytes);
+	};
+	
+};
+
+module.exports = audioProcessor;

lib/rtp.js

@@ -1,4 +1,6 @@
 var dgram = require('dgram');
+var tools = require('./rtsphelper');
+var crypto = require('crypto');
 
 var rtpServer = function(rtspServer) {
 	var self = this;
@@ -13,16 +15,28 @@ var rtpServer = function(rtspServer) {
 	};
 
 	baseServer.on('message', function(msg) {
-		//console.log(msg.length + ' BYTES SENT TO SERVER PORT');
+		var meta = msg.slice(0, 12);
+		var sequenceNumber = meta.slice(2, 4).readUInt16BE(0);
+		console.log(sequenceNumber + "; ");
+		console.log(meta.slice(2, 4));
+
+		var encryptedAudio = msg.slice(12);
+
+		var decipher = crypto.createDecipheriv('aes-128-cbc', rtspServer.audioAesKey, rtspServer.audioAesIv);
+		decipher.setAutoPadding(false);
+
+		var audio = decipher.update(encryptedAudio);
+
+		console.log(audio);
+
+		rtspServer.audioProcessor.process(audio);
 	});
 	controlServer.on('message', function(msg) {
 		console.log(msg.length + ' BYTES SENT TO CONTROL PORT');
 	});
 	timingServer.on('message', function(msg) {
 		console.log(msg.length + ' BYTES SENT TO TIMING PORT');
 	});
-
-	return self;
 }
 
 module.exports = rtpServer;

lib/rtsp.js

@@ -4,6 +4,7 @@ var ip = require('ip');
 var tools = require('./rtsphelper');
 var getmac = require('getmac');
 var RtpServer = require('./rtp');
+var AudioProcessor = require('./audioprocessor');
 
 var errorList = {
 	400: "BAD REQUEST"
@@ -17,7 +18,8 @@ var server = function() {
 	self.controlPort = 63379;
 	self.timingPort = 50607;
 
-	self.rtp = RtpServer(self);
+	self.rtp = new RtpServer(self);
+	self.audioProcessor = new AudioProcessor(self);
 
 	// pull method processors
 	var methodMapping = require('./rtspmethods')(self);

lib/rtsphelper.js

@@ -33,8 +33,32 @@ var messageBuilder = function(socket) {
 	};
 };
 
+var parseSdp = function(msg) {
+	var multi = [ 'a', 'p', 'b' ];
+
+	var lines = msg.split('\r\n');
+	var output = {};
+	for (var i = 0; i < lines.length; i++) {
+
+		var sp = lines[i].split(/=(.+)?/);
+		if (sp.length == 3) { // for some reason there's an empty item?
+			if (multi.indexOf(sp[0]) != -1) { // some attributes are multiline...
+				if (!output[sp[0]])
+					output[sp[0]] = new Array();
+
+				output[sp[0]].push(sp[1]);
+			} else {
+				output[sp[0]] = sp[1];
+			}
+		}
+	}
+	return output;
+};
+
+var privkey = ursa.createPrivateKey(fs.readFileSync('private.key'));
+
 var generateAppleResponse = function(challengeBuf, ipAddr, macAddr) {
-	macAddr = new Buffer('5F513885F785', 'hex');
+	macAddr = new Buffer('5F513885F785', 'hex'); // inject?
 	var fullChallenge = Buffer.concat([ challengeBuf, ipAddr, macAddr ]);
 
 	// im sure there's an easier way to pad this buffer
@@ -44,11 +68,12 @@ var generateAppleResponse = function(challengeBuf, ipAddr, macAddr) {
 	}
 	fullChallenge = Buffer.concat([ fullChallenge, new Buffer(padding) ]);
 
-	var privkey = ursa.createPrivateKey(fs.readFileSync('private.key'));
 	var response = privkey.privateEncrypt(fullChallenge, 'base64', 'base64');
 
 	return response;
 };
 
+module.exports.parseSdp = parseSdp;
 module.exports.MessageBuilder = messageBuilder;
-module.exports.generateAppleResponse = generateAppleResponse;
+module.exports.generateAppleResponse = generateAppleResponse;
+module.exports.rsaOperations = privkey;

lib/rtspmethods.js

@@ -1,6 +1,7 @@
 
 var tools = require('./rtsphelper');
 var ip = require('ip');
+
 module.exports = function(rtspServer) {
 
 	var rtspServer = rtspServer;
@@ -25,6 +26,21 @@ module.exports = function(rtspServer) {
 	};
 
 	var announce = function(response, headers, content) {
+		var sdp = tools.parseSdp(content);
+		for (var i = 0; i < sdp.a.length; i++) {
+			var sp = sdp.a[i].split(':');
+			if (sp.length == 2) {
+				if (sp[0] == 'rsaaeskey') {
+					rtspServer.audioAesKey = tools.rsaOperations.decrypt(new Buffer(sp[1], 'base64'));
+				} else if (sp[0] == 'aesiv') {
+					rtspServer.audioAesIv = new Buffer(sp[1], 'base64');
+				} else if (sp[0] == 'rtpmap') {
+					rtspServer.audioCodec = sp[1];
+				}
+			}
+		}
+		rtspServer.clientName = sdp.i;
+
 		response.setOK(headers['CSeq']);
 		response.send();
 	};

lib/start.js

@@ -7,7 +7,7 @@ var txtSetup = {
 	txtvers: '1', 		// txt record version?
 	tx: '1',			// ?
 	ch: '2',			// # channels
-	cn: '0,2',			// codec; 0=pcm, 1=alac, 2=aac, 3=aac elc; fwiw Sonos supports aac; pcm required for iPad+Spotify; OS X works with pcm
+	cn: '0',			// codec; 0=pcm, 1=alac, 2=aac, 3=aac elc; fwiw Sonos supports aac; pcm required for iPad+Spotify; OS X works with pcm
 	et: '0,1',			// encryption; 0=none, 1=rsa, 3=fairplay, 4=mfisap, 5=fairplay2.5; need rsa for os x
 	md: '0',			// metadata; 0=text, 1=artwork, 2=progress
 	pw: 'false',		// password enabled
@@ -17,7 +17,7 @@ var txtSetup = {
 	vs: '130.14',		// server version?
 	am: 'AirSonos',		// device model
 
-	ek: '1',			// ? from ApEx; setting to 1 enables iTunes
+	ek: '1',			// ? from ApEx; setting to 1 enables iTunes; seems to use ALAC regardless of 'cn' setting
 	//sv: 'false',		// ? from ApEx
 	//da: 'true', 		// ? from ApEx
 	//vn: '65537',		// ? from ApEx; maybe rsa key modulus? happens to be the same value