Question

我正在使用Web Audio API创建基于Recorderjs的网络录音机。目前，我的录像机似乎在Firefox上工作得很好。我遇到的问题是，在Chrome上，我的程序似乎记录了音频（或者至少记录了正确的时间），但是当我尝试播放录音时，将其编码为WAV文件后，音频似乎是录音最后一个声音的连续循环，但仍然可以播放正确的时间。

非常感谢任何帮助！

以下是相关代码：

//toggle recording
function recordButton() {
//if not currently recording already
if (recording === false) {
    //if this is initial recording
    if (!somethingRecorded) {
        arrayPos.push(0);        //recLength at 0 sceonds is also 0
    }

    //check if dictation is being played
    if (playing) {
        //if it is, then first pause audio
        dictation.pause();
        playing = false;
    }

    //if need to record over previous audio
    if (timeBar.value < timeBar.max) {
        console.log("In rewound block");

        seconds = Number(timeBar.value);   //convert to number since timeBar.value is a string

        //erase buffers after place where rewound to
        var index = timeBar.value / 0.1;      //calculate index in arrayPos that the value for the current time will be, since values are pushed into arrayPos every 0.1 seconds
        for (var i = numBuffers; i > arrayPos[index]; i--) {
            recLength -= recBuffersL[i - 1].length;
            recBuffersL.pop();
            recBuffersR.pop();
            numBuffers--;
        }

    }

    console.log("Start Record");
    recording = true;
    timeBar.max = 300;
    intervalID = setInterval(updateTime, 100);
    somethingRecorded = true;

    //disable buttons
    disableButtons([0, 0, 1, 0, 0, 0]);

}
else {
    console.log("Stop Record");
    recording = false;
    clearInterval(intervalID);
    timeBar.max = timeBar.value;
    window.document.getElementById("maxtime").innerHTML = Math.floor(timeBar.max / 60) + ":" + ("0" + Math.floor(timeBar.max % 60) ).slice(-2);

    //disable buttons and save audio
    disableButtons([0, 0, 0, 1, 0, 0]);
    saveAudio();
}
}

//save audio file
function saveAudio(fileType) {
fileType = fileType || 'audio/wav';

//flatten out the input channels
var mergedL = new Float32Array(recLength);
var mergedR = new Float32Array(recLength);

offset = 0;
for (var i = 0; i < recBuffersL.length; i++)     //both arrays should have same length
{
    mergedL.set(recBuffersL[i], offset);
    mergedR.set(recBuffersR[i], offset);
    offset += recBuffersL[i].length;
}

//combine two channels of input into one single sample
var combined = new Float32Array(mergedL.length + mergedR.length);

for (var i = 0; i < mergedL.length + mergedR.length; i += 2) {
    combined[i] = mergedL[i / 2];
    combined[i + 1] = mergedR[i / 2];
}

console.log(combined);
//encode sample into WAV format 
var dataview = encodeWAV(combined);

//final binary blob, then call functions to set up playback and download
var audioBlob = new Blob([dataview], { type: fileType });
var blobURL = (window.URL || window.webkitURL).createObjectURL(audioBlob);

setUpPlayback(blobURL);
//    doneEncoding(audioBlob);
}

//helper function for writing strings into DataView
function writeString(view, offset, string) {
for (var i = 0; i < string.length; i++) {
    view.setUint8(offset + i, string.charCodeAt(i));
}
}

//encode into WAV file  
function encodeWAV(audio) {
//create buffer and view to create WAV file
var buffer = new ArrayBuffer(44 + audio.length * 2);
var view = new DataView(buffer);

// RIFF identifier 
writeString(view, 0, 'RIFF');
// file length 
view.setUint32(4, 32 + audio.length * 2, true);
// RIFF type 
writeString(view, 8, 'WAVE');
// format chunk identifier 
writeString(view, 12, 'fmt ');
// format chunk length 
view.setUint32(16, 16, true);
// sample format (raw) 
view.setUint16(20, 1, true);
// channel count 
view.setUint16(22, 2, true);
// sample rate 
view.setUint32(24, sampleRate, true);
// byte rate (sample rate * block align) 
view.setUint32(28, sampleRate * 4, true);
// block align (channel count * bytes per sample) 
view.setUint16(32, 4, true);
// bits per sample 
view.setUint16(34, 16, true);
// data chunk identifier 
writeString(view, 36, 'data');
// data chunk length 
view.setUint32(40, audio.length * 2, true);

//write PCM samples
var index = 44;
for (var i = 0; i < audio.length; i++) {
    view.setInt16(index, audio[i] * (0x7FFF), true);
    index += 2;
}

return view;
}

Answer 1

万一有人遇到同样的问题，我想出来了。问题实际上是在inaudioprocess函数中。由于getChannelData实际上返回的是指针而不是实际的数组，因此在将数据推入包含缓冲区的数组之前，必须将数据克隆到Float32Array中。

Web Audio API Recording可在Firefox中使用，但不适用于Chrome

1 个答案: