javascript - 如何使用 ScriptProcessorNode 执行简单的线性重采样？

Question

我目前正在尝试使用 ScriptProcessorNode 动态降低播放速度。这是我迄今为止编写的代码(仅处理左 channel ):

let processor = audioContext.createScriptProcessor(2**14);
let stored = [];
let currIndex = 0;
let playbackRate = 0.666;

processor.onaudioprocess = (e) => {
    let leftChannel = e.inputBuffer.getChannelData(0);
    for (let i = 0; i < leftChannel.length; i++) stored.push(leftChannel[i]);
    let outputLeft = e.outputBuffer.getChannelData(0);

    for (let i = 0; i < outputLeft.length; i++) {
        let otherIndex = currIndex + i * playbackRate;
        let completion = otherIndex % 1;
        let otherSampleLow = stored[Math.floor(otherIndex)];
        let otherSampleHigh = stored[Math.ceil(otherIndex)];

        let val = (completion-1)*otherSampleLow + completion*otherSampleHigh;
        outputLeft[i] = val;
    }

    currIndex += Math.floor(leftChannel.length * playbackRate);
};

let osc = audioContext.createOscillator();
osc.frequency.value = 440;
osc.connect(processor);
osc.start();

然而，对于任何小于 1 的播放速率来说，这听起来完全是垃圾。为什么呢？我是否太天真地认为只需在信号之间进行线性插值就可以减慢音频信号的速度？

这是一个 fiddle :https://jsfiddle.net/6Le7aq42/

Answer 1

明白了，错误是写了 (completion - 1) 而不是 (1 - Completion)。