Web音频分析器节点-定期运行 [英] Web audio analyser node - run at regular interval

问题描述

我想使用在特定频率上检测音频信号(摩尔斯电码)网络音频.我使用分析器节点的getFloatFrequencyData函数检索频率数据.

I want to detect an audio signal (morse code) on specific frequencies using web audio. I retrieve the frequency data using an analyser node's getFloatFrequencyData function.

现在的问题是:使用setInterval()定期采样频率数据还不够规则:回调比预期的要早或晚执行几毫秒.

Now the problem: Using setInterval() to regularly sample the frequency data is not regular enough: the callback gets executed a few milliseconds earlier or later than expected.

我如何才能每隔几毫秒定期准确地获取分析仪的频率数据?我更喜欢使用内置分析仪节点的FFT功能，而不是借助例如手动处理音频数据的方法. Goertzel 算法.

How can I retrieve the analyser's frequency data regularly exactly every few miliseconds? I would prefer using the built-in analyser node's FFT functionality instead of resorting to manually processing the audio data via e.g. Goertzel algorithm.

有问题的setInterval()的代码示例:

Code sample with the problematic setInterval():

// Analyse microphone audio frequencies: 
function onStream(stream) {
  let audioCtx = new(window.AudioContext || window.webkitAudioContext)(),
    source = audioCtx.createMediaStreamSource(stream),
    analyser = audioCtx.createAnalyser(),
    fft = new Float32Array(analyser.frequencyBinCount);

  source.connect(analyser);

  // Doesn't execute exactly every 100ms as needed - what to do?
  setInterval(() => {
    analyser.getFloatFrequencyData(fft);
    console.log(performance.now(), fft[0]);
  }, 100);
}

navigator.mediaDevices.getUserMedia({audio: true}).then(onStream);

推荐答案

是的，您不能真正使用分析仪.它什么时候开始运行存在太多不确定性，您不能保证它何时才能准确运行.您最好暂时使用ScriptProcessor(最终使用AudioWorklet)，然后自己进行FFT(或其他识别代码).

Yeah, you can't really use an analyzer. There's too much uncertainty in when it will get run, and you can't guarantee precisely when it will run. You're better off using a ScriptProcessor for now (AudioWorklet eventually), and doing the FFT (or other recognition code) yourself.

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