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 which results in large files. I am looking for a way to record with JS directly to MP3, or encode the bits somehow to MP3 instead of WAV.
How can it be done? Is there a Web Audio API function that can do that or JS MP3 encoder of some sort?
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.
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
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
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.
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.
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.
来源：https://stackoverflow.com/questions/16881703/web-audio-api-record-to-mp3