在Javascript中更改录音的采样率

Question

您好我在浏览器上有一个工作语音录音机。它实现了navigator.getUserMedia和AudioContext 它以.wav格式记录声音 - 然后转换为.mp3并上传文件。

文件采样率设置为44100Hz，mp3输出重新采样为8000Hz。问题在于以此采样率记录大型音频文件所需的本地存储量。我通过转换为MP3缩小文件大小，采样率为8000。 我读到sampleRate是只读的。所以我想可以在实例化时设置采样率。我的问题是如何使用javascript更改录音机上的采样率？

NB。下面的代码已被修剪以显示感兴趣的部分。

    try{
    window.AudioContext = window.AudioContext || window.webkitAudioContext;
    navigator.getMedia = ( navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.msGetUserMedia);
    window.URL = window.URL || window.webkitURL;
    audioCtx = new AudioContext;
    var buffer = audioCtx.createBuffer(1, 8000, 8000);// this does not work!
    }
    catch (e)
    {
        console.log('unable to create a audiocontext');
        exit;
    }
    navigator.getMedia({audio: true}, startUserMedia, function(e) {
                    console.log('No live audio input: ' + e);}
                );
    function startUserMedia(stream) {
        var input = audioCtx.createMediaStreamSource(stream);
        console.log('Media stream created.' );
        console.log("input sample rate " +input.context.sampleRate);
        input.connect(audioCtx.destination);
        console.log('Input connected to audio context destination.');
        recorder = new Recorder(input);
        console.log('Recorder initialised.');
        var mediaStreamSource = audioCtx.createMediaStreamSource(stream);
        var analyser = audioCtx.createAnalyser();
        analyser.smoothingTimeConstant = 0.3;
        analyser.fftSize = 2048;
        var javascriptNode = audioCtx.createScriptProcessor(2048, 1, 1);
        mediaStreamSource.connect(analyser);
        analyser.connect(javascriptNode);
        javascriptNode.connect(audioCtx.destination);
        javascriptNode.onaudioprocess = visualiser(analyser);
    }