lamejs

    1.2.0 • Public • Published

    lamejs

    Fast mp3 encoder written in JavaScript. On my machine it works 20x faster than realtime (it will encode 132 second long sample in 6.5 seconds) both on node and chrome. lamejs is a rewrite of jump3r-code which is a rewrite of libmp3lame.

    Installation

    To install via Bower or npm, simply do the following:

    $ bower install lamejs --save
    $ npm install lamejs

    Quick Start

    <script src='lame.all.js'></script>
    <script>
    var mp3Data = [];
     
    var mp3encoder = new lamejs.Mp3Encoder(1, 44100, 128); //mono 44.1khz encode to 128kbps
    var samples = new Int16Array(44100); //one second of silence replace that with your own samples
    var mp3Tmp = mp3encoder.encodeBuffer(samples); //encode mp3
     
    //Push encode buffer to mp3Data variable
    mp3Data.push(mp3Tmp);
     
    // Get end part of mp3
    mp3Tmp = mp3encoder.flush();
     
    // Write last data to the output data, too
    // mp3Data contains now the complete mp3Data
    mp3Data.push(mp3Tmp);
     
    console.debug(mp3Data);
    </script>

    To use lamejs in Node.js build, you can install it from npm:

    npm install lamejs
    

    Then use it:

    var lamejs = require("lamejs");
    

    Real Example

    Either see example.html for full example of wav file encoding in browser or use this:

    <script src='lame.all.js'></script>
    <script>
    channels = 1; //1 for mono or 2 for stereo
    sampleRate = 44100; //44.1khz (normal mp3 samplerate)
    kbps = 128; //encode 128kbps mp3
    mp3encoder = new lamejs.Mp3Encoder(channels, sampleRate, kbps);
    var mp3Data = [];
     
    samples = new Int16Array(44100); //one second of silence (get your data from the source you have)
    sampleBlockSize = 1152; //can be anything but make it a multiple of 576 to make encoders life easier
     
    var mp3Data = [];
    for (var i = 0; i < samples.length; i += sampleBlockSize) {
      sampleChunk = samples.subarray(i, i + sampleBlockSize);
      var mp3buf = mp3encoder.encodeBuffer(sampleChunk);
      if (mp3buf.length > 0) {
          mp3Data.push(mp3buf);
      }
    }
    var mp3buf = mp3encoder.flush();   //finish writing mp3
     
    if (mp3buf.length > 0) {
        mp3Data.push(new Int8Array(mp3buf));
    }
     
    var blob = new Blob(mp3Data, {type: 'audio/mp3'});
    var url = window.URL.createObjectURL(blob);
    console.log('MP3 URl: ', url);
    </script>

    Stereo

    If you want to encode stereo mp3 use separate sample buffers for left and right channel

    <script src='lame.all.js'></script>
    <script>
    mp3encoder = new lamejs.Mp3Encoder(2, 44100, 128);
    var mp3Data = [];
     
    left = new Int16Array(44100); //one second of silence (get your data from the source you have)
    right = new Int16Array(44100); //one second of silence (get your data from the source you have)
    sampleBlockSize = 1152; //can be anything but make it a multiple of 576 to make encoders life easier
     
    for (var i = 0; i < samples.length; i += sampleBlockSize) {
      leftChunk = left.subarray(i, i + sampleBlockSize);
      rightChunk = right.subarray(i, i + sampleBlockSize);
      var mp3buf = mp3encoder.encodeBuffer(leftChunk, rightChunk);
      if (mp3buf.length > 0) {
        mp3Data.push(mp3buf);
      }
    }
    var mp3buf = mp3encoder.flush();   //finish writing mp3
     
    if (mp3buf.length > 0) {
        mp3Data.push(mp3buf);
    }
     
    console.log(mp3Data);
    </script>

    Install

    npm i lamejs

    DownloadsWeekly Downloads

    14,219

    Version

    1.2.0

    License

    LGPL-3.0

    Last publish

    Collaborators

    • zhuker