How to set up sample rate using web audio API?

问题

I have blob type generated by webaudio API, but the file that is saved have to high sample rate. How can I convert it to lower maybe something like https://developer.mozilla.org/en-US/docs/Web/API/OfflineAudioContext can help? Here is some sample of code:

  var xhr = new XMLHttpRequest();
   /* HERE IS SOME CONVERTATION TO LOWER RATE */

    var fd = new FormData();

    fd.append("randomname", bigBlob);
    xhr.open("POST",url,false);
    xhr.send(fd);

    xhr.onload=function(e) {
        alert(e.target.responseText);
    };

回答1:

Create an OfflineAudioContext with the rate you want at the end, and the number of frames there will be at the end
Create an AudioBuffer from your raw data buffer
Create an AudioBufferSourceNode, set its buffer attribute to the AudioBuffer you just created, and connect this AudioBufferSourceNode to the destination of the OfflineAudioContext
Start the AudioBufferSourceNode at 0
Start the rendering

回答2:

I couldn't find a way to control the sample rate but here is a way to re-sample (up/down sampling)

function reSample(audioBuffer, targetSampleRate, onComplete) {
    var channel = audioBuffer.numberOfChannels;
    var samples = audioBuffer.length * targetSampleRate / audioBuffer.sampleRate;

    var offlineContext = new OfflineAudioContext(channel, samples, targetSampleRate);
    var bufferSource = offlineContext.createBufferSource();
    bufferSource.buffer = audioBuffer;

    bufferSource.connect(offlineContext.destination);
    bufferSource.start(0);
    offlineContext.startRendering().then(function(renderedBuffer){
        onComplete(renderedBuffer);
    })
}

Extracted from here: https://github.com/notthetup/resampler

来源：https://stackoverflow.com/questions/28821124/how-to-set-up-sample-rate-using-web-audio-api

标签

web-audio-api