Web audio API downsample 44.1 khz in Javascript - audio

Question

I'm using RecorderJS to record a microphone stream from the user. The default export is a WAV file at 44.1 kHz, 16bit. Is there anyway I can downsample this to 11kHz or 16kHz without it sounding weird?
Is there anyway I can get a 16bit 16khz WAV file out of a Web Audio API getUserMedia stream, by using only javascript?
I'm trying to reduce the file size, thus saving a lot of bandwidth for the users. Thanks.

Answer 1

Edit : one more thing, you can also, send only one channel instead of both...
I am not sure if this is the right way, but I did by doing interpolation of the data received from microphone,
I am guess, you are capturing your data from microphone something like this,
this.node.onaudioprocess = function(e){
if (!recording) return;
worker.postMessage({
command: 'record',
buffer: [
e.inputBuffer.getChannelData(0),
e.inputBuffer.getChannelData(1)
]
});
}
now modify it into
var oldSampleRate = 44100, newSampleRate = 16000;
this.node.onaudioprocess = function(e){
var leftData = e.inputBuffer.getChannelData(0);
var rightData = e.inputBuffer.getChannelData(1);
leftData = interpolateArray(leftData, leftData.length * (newSampleRate/oldSampleRate) );
rightData = interpolateArray(rightData, rightData.length * (newSampleRate/oldSampleRate) );
if (!recording) return;
worker.postMessage({
command: 'record',
buffer: [
leftData,
rightData
]
});
}
function interpolateArray(data, fitCount) {
var linearInterpolate = function (before, after, atPoint) {
return before + (after - before) * atPoint;
};
var newData = new Array();
var springFactor = new Number((data.length - 1) / (fitCount - 1));
newData[0] = data[0]; // for new allocation
for ( var i = 1; i < fitCount - 1; i++) {
var tmp = i * springFactor;
var before = new Number(Math.floor(tmp)).toFixed();
var after = new Number(Math.ceil(tmp)).toFixed();
var atPoint = tmp - before;
newData[i] = linearInterpolate(data[before], data[after], atPoint);
}
newData[fitCount - 1] = data[data.length - 1]; // for new allocation
return newData;
};