websockets-streaming-audio

websockets-streaming-audio

Stream audio to a Web Audio API enabled browser from Node.js server side using Web Worker and Web Socket.

My plan is to make this modular enough to get added to your process as simple API calls - using Angularjs ;-)

I have now introduced a Web Worker to handle all server side calls - this fixed glitches of early versions suffered due to the single threaded browser - This outlines the flow of control :

Browser      <-->     Web Worker      <-->      Web Socket    <-->    Node.js

mode 1 Fill up audio queue on browser by requesting server side to start streaming the media file and return floating point typed array buffers via Web Worker using Web Sockets - transition to mode 2 when browser queue is full

mode 2 Browser renders audio using Web Audio API by consuming buffers from browser buffer queue. Simultaneously, the Web Worker is told to replenish its own WW side audio buffer queue by requesting buffers from Node.js server side using Web Socket - transition to mode 3 when browser buffer queue gets too low

mode 3 Browser seamlessly continues to render audio by consuming its same browser buffer queue. Web Worker does not interact with Node.js server side in this mode (critical to avoid interruptions). Web Worker begins this mode with a full buffer queue replinished during mode 2. Driven from the Web Audio API event loop callback, browser requests WW to send typed array audio buffers which refills its browser buffer queue at twice its consumption rate. - transition to mode 2 when browser audio buffer queue is full

[https://github.com/scottstensland/websockets-streaming-audio](github repo)

Installation

visit nodejs.org and install node.js

see project npm site at

https://www.npmjs.org/package/websockets-streaming-audio

Clone this repository to your local machine:

npm install websockets-streaming-audio

Change directory into the project folder websockets-streaming-audio

Then install the dependent modules:

npm install

Launch the nodejs app:

npm start

Using a Web Audio API savvy browser (ff/chrome), point it at URL :

		 http://localhost:8888 

now in your browser (firefox/chrome) click stream_audio

or ignore above and just see this WebGL app deployed live on heroku :

http://websockets-streaming-audio.herokuapp.com

Current Limitations - server side source media parser I wrote only handles WAV format, however now that I am using Web Worker I could transition to a compressed format. The bloated ogg decoder enabled using emscripten may go in soon dunno. - I am not a front end developer so please click reload in between each stream button hit until I teach myself Angularjs ;-)))

Lessions Learned - To stream using Web Audio API you must offload Web Socket calls to the server side by the introduction of a Web Worker layer

Feel free to contact me on twitter if you have any questions! :) @scottstensland