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javascript - Get 16 bit output audio using AudioContext

问题描述

requirement : Container WAV Encoding PCM Rate 16K Sample Format 16 bit Channels Mono

My output : Container WAV Encoding PCM Rate 16K Sample Format 32 bit float Channels Mono

I need to get an audio output with a sample format of 16-bit PCM, currently the only output i get is 32-bit FLOAT

My code : 

URL = window.URL || window.webkitURL;
var gumStream;
//stream from getUserMedia() 
var rec;
//Recorder.js object 
var input;
//MediaStreamAudioSourceNode we'll be recording 
// shim for AudioContext when it's not avb. 

//new audio context to help us record 
var recordButton = document.getElementById("recordButton");
var stopButton = document.getElementById("stopButton");
var pauseButton = document.getElementById("pauseButton");

var recordButton_ = document.getElementById("recordButton_");
var stopButton_ = document.getElementById("stopButton_");
var pauseButton_ = document.getElementById("pauseButton_");
//add events to those 3 buttons 
recordButton.addEventListener("click", startRecording);
stopButton.addEventListener("click", stopRecording);
pauseButton.addEventListener("click", pauseRecording);

function startRecording() { 

    var AudioContext = (window.AudioContext) || (window.webkitAudioContext)

var audioContext = new AudioContext({
    sampleRate: 16000,
  });

    console.log("recordButton clicked");

/* Simple constraints object, for more advanced audio features see

https://addpipe.com/blog/audio-constraints-getusermedia/ */

var constraints = {
    audio: true,
    video: false
} 
/* Disable the record button until we get a success or fail from getUserMedia() */

recordButton.disabled = true;
stopButton.disabled = false;
pauseButton.disabled = false

/* We're using the standard promise based getUserMedia()

https://developer.mozilla.org/en-US/docs/Web/API/MediaDevices/getUserMedia */

navigator.mediaDevices.getUserMedia(constraints).then(function(stream) {
    console.log("getUserMedia() success, stream created, initializing Recorder.js ..."); 
    /* assign to gumStream for later use */
    gumStream = stream;
    /* use the stream */
    input = audioContext.createMediaStreamSource(stream);
    /* Create the Recorder object and configure to record mono sound (1 channel) Recording 2 channels will double the file size */
    rec = new Recorder(input, {
        numChannels: 1
    }) 
    //start the recording process 
    rec.record()
    console.log("Recording started");
}).catch(function(err) {
    //enable the record button if getUserMedia() fails 
    recordButton.disabled = false;
    stopButton.disabled = true;
    pauseButton.disabled = true
});
}

function pauseRecording() {
    console.log("pauseButton clicked rec.recording=", rec.recording);
    if (rec.recording) {
        //pause 
        rec.stop();
        pauseButton.innerHTML = "Resume";
    } else {
        //resume 
        rec.record()
        pauseButton.innerHTML = "Pause";
    }
}

function stopRecording() {
    console.log("stopButton clicked");
    //disable the stop button, enable the record too allow for new recordings 
    stopButton.disabled = true;
    recordButton.disabled = false;
    pauseButton.disabled = true;
    //reset button just in case the recording is stopped while paused 
    pauseButton.innerHTML = "Pause";
    //tell the recorder to stop the recording 
    rec.stop(); //stop microphone access 
    gumStream.getAudioTracks()[0].stop();
    //create the wav blob and pass it on to createDownloadLink 
    rec.exportWAV(createDownloadLink);
}

function createDownloadLink(blob) {
    var url = URL.createObjectURL(blob);
    var au = document.createElement('audio');
    var li = document.createElement('li');
    var link = document.createElement('a');
    //add controls to the <audio> element 
    au.controls = true;
    au.src = url;
    au.sampleRate = 16000
    //link the a element to the blob 
    link.href = url;
    // link.download = new Date().toISOString() + '.wav';
    link.innerHTML = link.download;
    //add the new audio and a elements to the li element 
    li.appendChild(au);
    li.appendChild(link);
    //add the li element to the ordered list 
    recordingsList.appendChild(li);
    var p = document.createElement("br");
    recordingsList.appendChild(p);

}

标签： javascriptaudiocontext

解决方案

您的代码没有任何问题，默认情况下 Web Audio API 提供的输出是 32 位的，您需要使用BitCrusher文档中描述的节点来处理它：

https://webaudio.github.io/web-audio-api/#the-bitcrusher-node

希望这可以帮助。

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