ESP32-P4_DANTE/docs/dante-aes67-relay.js

const dgram = require('dgram');
const client = dgram.createSocket({ type: 'udp4', reuseAddr: true });
const sdp = require('./sdp');

//config
const addr = '10.10.1.100';
const danteMulticast = '239.255.220.221';
const aes67Multicast = '239.69.1.122';
const samplerate = 48000;
const channels = 2;
const encoding = 'L24';
const name = 'Dante Multicast Relay';
const sessID = Math.round(Date.now() / 1000);
const sessVersion = sessID;
const ptpMaster = '08-00-00-ff-fe-00-00-1f:0';

//rtp specific vars
var seqNum = 0;

client.on('listening', function() {
	client.addMembership(danteMulticast, addr);
	client.setMulticastInterface(addr);
});

client.on('message', function(buffer, remote) {
	//read values from buffer
	var channelCount = buffer.readUInt8(0);
	var timestampSeconds = buffer.readUInt32BE(1);
	//bytes 6 and 7 seem to be always 0x00, maybe reserved bytes
	var timestampMedia = buffer.readUInt16BE(7);
	var pcmData = buffer.slice(9);

	//calculate media timestamp for rtp
	var timestampRTP = ((timestampSeconds * samplerate) + timestampMedia) & 0xffffffff;

	//create RTP header
	var rtpHeader = Buffer.alloc(12);
	rtpHeader.writeUInt16BE(0x8061, 0);
	rtpHeader.writeUInt16BE(seqNum, 2);
	rtpHeader.writeInt32BE(timestampRTP, 4);
	rtpHeader.writeUInt32BE(0xaf12af34, 8);

	//create and send RTP packet
	var rtpBuffer = Buffer.concat([rtpHeader, pcmData]);
	client.send(rtpBuffer, 5004, aes67Multicast);

	//increase seqnum
	seqNum = (seqNum + 1) % 65536;
});

client.bind(4321);
sdp.start(addr, aes67Multicast, samplerate, channels, encoding, name, sessID, sessVersion, ptpMaster);