Generate sine wave audio and output it to default audiodevice

sine.js

const { RtAudio, RtAudioFormat } = require('audify');
const rtAudio = new RtAudio();

// constants
const samplerate = 48000;
const ffp = 48;

// audio device
let audioOutput = {
	deviceId: rtAudio.getDefaultOutputDevice(),
	nChannels: 2, 
	firstChannel: 0
};

// Open the input/output stream
rtAudio.openStream(audioOutput, null, RtAudioFormat.RTAUDIO_SINT16, samplerate, ffp, 'Sine');

// Start the stream
rtAudio.start();

let pcm = Buffer.alloc(ffp * 2 * 2);
let index = 0;
let freq = 440;

// 50 ms buffering (silence)
for(let i = 0; i < 50; i++){
	rtAudio.write(pcm);
}

rtAudio.setFrameOutputCallback(function(){
	rtAudio.write(pcm);

	// generate sine wave buffer
	for(let i = 0; i < ffp; i++){
		let sine = 32767 * Math.sin(2 * freq * Math.PI * index/samplerate);

		pcm.writeInt16LE(sine, 4*i);
		pcm.writeInt16LE(sine, 4*i + 2);
		index = (index + 1) % (samplerate + 1);
	}
});