Web Audio API - record to MP3?

Question

I am asking because I couldn\'t find the answer anywhere. I have successfully implemented RecorderJS in order to record microphone input in JS. However, the recorded file is WAV

Answer 1

Encoding into smaller formats is currently only supported by Firefox:

• http://w3c.github.io/mediacapture-record/MediaRecorder.html
• https://developer.mozilla.org/en-US/docs/Web/API/MediaRecorder

Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit) Not supported 25.0 (25.0) Not supported Not supported Not supported

AFAIK only OGG is supported. But better OGG than WAV.

Answer 2

To record mp3 using javascript without any other framework using a web worker, you can use this project: https://github.com/nusofthq/Recordmp3js which is also very well explained here:

http://audior.ec/blog/recording-mp3-using-only-html5-and-javascript-recordmp3-js/

With this, it's also possible to write to a .mp3 file and to make it downloadable.

Answer 3

I have found a nice library with live demos: MediaStreamRecorder

One of demos is here: Audio Recording

RecordRTC is also can be useful but MSR it seems is easier to start with.

Answer 4

I was frustrated with this problem, and existing solutions, so I came up with something simpler:

https://github.com/sb2702/audioRecord.js

Usage

Create a recorder object (async because requires user permission)

    Recorder.new(function(recorder){ 

    }); 

Start recording

         recorder.start();        

Stops recording

         recorder.stop();    

Export as mp3

         recorder.exportMP3(function(mp3Blob){ 

            console.log("Here is your blob: " + URL.createObjectURL(mp3Blob));

          });

Mostly based on RecorderJS, but changed some things around to export to mp3 files, and to not have to muck around with AudioContext / navigator.getUs

Answer 5

The only Javascript MP3 encoder I've seen is https://github.com/akrennmair/libmp3lame-js, which is a port using emscripten. It's supposed to be slow, and I've never used it.

I don't know of any natively-written Javascript MP3 encoders, and encoding is not covered by the Web Audio API.

Answer 6

There's a library written in pure javascript, called lamejs. To encode mp3s from raw audio. It is much faster than emscripten compile of libmp3lame. https://github.com/zhuker/lamejs

Example usage:

lib = new lamejs();
mp3encoder = new lib.Mp3Encoder(1, 44100, 128); //mono 44.1khz encode to 128kbps
samples = new Int16Array(44100); //one second of silence
var mp3 = mp3encoder.encodeBuffer(samples); //encode mp3