[英]Downsampling a PCM audio buffer in javascript
我正在嘗試對從audioContext獲取的采樣率進行下采樣。 我相信它是在44100,我希望它是11025.我想我可以平均每3個樣本並以正確的速率播放,但是音高太高,好像我們都在氦氣。
在11025樣本中將float32Array從44100下采樣到int16Array的正確方法是什么?
var context = new Flash.audioContext();
var audioInput = context.createMediaStreamSource(stream);
var recorder = context.createScriptProcessor(null, 1, 1);
recorder.onaudioprocess = onAudio;
audioInput.connect(recorder);
recorder.connect(context.destination);
var onAudio = function (e) {
var left = e.inputBuffer.getChannelData(0);
bStream.write(Flash.convertFloat32ToInt16(left));
}
var convertFloat32ToInt16 = function(buffer) {
var l = buffer.length;
var point = Math.floor(l/3);
var buf = new Int16Array(point);
for (var x = l; x > 0;) {
var average = (buffer[x] + buffer[x-1] + buffer[x-2]) / 3;
buf[point] = average*0x7FFF;
point -= 1;
x -= 3;
}
return buf.buffer;
}
對於任何需要答案的人。
var downsampleBuffer = function (buffer, sampleRate, outSampleRate) {
if (outSampleRate == sampleRate) {
return buffer;
}
if (outSampleRate > sampleRate) {
throw "downsampling rate show be smaller than original sample rate";
}
var sampleRateRatio = sampleRate / outSampleRate;
var newLength = Math.round(buffer.length / sampleRateRatio);
var result = new Int16Array(newLength);
var offsetResult = 0;
var offsetBuffer = 0;
while (offsetResult < result.length) {
var nextOffsetBuffer = Math.round((offsetResult + 1) * sampleRateRatio);
var accum = 0, count = 0;
for (var i = offsetBuffer; i < nextOffsetBuffer && i < buffer.length; i++) {
accum += buffer[i];
count++;
}
result[offsetResult] = Math.min(1, accum / count)*0x7FFF;
offsetResult++;
offsetBuffer = nextOffsetBuffer;
}
return result.buffer;
}
這將返回小於傳遞給它的采樣率,同時還將其轉換為int16Array而不是float32。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.