你如何同步的JavaScript动画与歌曲的节奏，没有建立一个＆QUOT;音频可视化和QUOT ;? [英] How do you sync JavaScript animations with the tempo of a song, without building an "audio visualizer"?

问题描述

从我的基本的了解，JavaScript的音频可视化工具是基于实际的声波反射的音乐。我想建立像节拍器（http://bl.ocks.org/1399233），在那里我每天动画 X 拍一些DOM元素。

From my basic understanding, JavaScript audio visualizers are reflecting the music based on the actual sound waves. I would like to build something like a metronome (http://bl.ocks.org/1399233), where I animate some DOM element every x beats.

我这样做，现在是我手动计算出乐曲的速度的方式，说这是120BPM，那么我将其转换为毫秒运行的setInterval 回调。但是，这似乎并没有工作，因为浏览器的性能，导致其对IM precise。有没有更好的办法，以确保在同一节奏的歌曲是准确执行的回调？

The way I'm doing this now is I manually figure out the tempo of the song, say it's 120bpm, then I convert that to milliseconds to run a setInterval callback. But that doesn't seem to work because the browser performance causes it to be imprecise. Is there a better way to make sure a callback is executed exactly at the same tempo a song is in?

如果不是，那么其他一些策略，以同步与歌曲的节奏JavaScript的动画，这不是一个音频可视化工具？

If not, what are some other strategies to sync JavaScript animations with a song's tempo that's not an audio visualizer?

更新：是这样的，它看起来像？ https://github.com/bestiejs/benchmark.js/blob /master/benchmark.js#L1606

Update: something like this it looks like? https://github.com/bestiejs/benchmark.js/blob/master/benchmark.js#L1606

推荐答案

我也有类似的问题，即的setInterval 不能上依赖于保持时间过期长。我的解决方案是下面的代码片段：（咖啡脚本编译JS是在结尾的链接）

I had a similar problem, in that setInterval could not be relied on to "keep time" over a long period. My solution was the snippet below: (in coffee script, compiled js is in the link at the end)

它提供了替代setInetrval下降，将保持非常接近保持时间。有了它，你可以这样做：

It provides a drop in replacement for setInetrval that will stay very close to keeping time. With it, you can do this:

accurateInterval(1000 * 60 / bpm, callbackFunc);

请参阅我的使用案例和例子，同步以提供BPM在这里YouTube视频的视觉效果：<一href=\"http://squeegy.github.com/MandalaTron/?bpm=64&vid=EaAzRm5MfY8&vidt=0.5&fullscreen=1\">http://squeegy.github.com/MandalaTron/?bpm=64&vid=EaAzRm5MfY8&vidt=0.5&fullscreen=1

See my use case and example that syncs visuals with a provided BPM to a youtube video here: http://squeegy.github.com/MandalaTron/?bpm=64&vid=EaAzRm5MfY8&vidt=0.5&fullscreen=1

accurateInterval code：

accurateInterval code:

# Accurate Interval, guaranteed not to drift!
# (Though each call can still be a few milliseconds late)
window.accurateInterval = (time, fn) ->

  # This value is the next time the the timer should fire.
  nextAt = new Date().getTime() + time

  # Allow arguments to be passed in in either order.
  if typeof time is 'function'
    [fn, time] = [time, fn]

  # Create a function that wraps our function to run.  This is responsible for
  # scheduling the next call and aborting when canceled.
  wrapper = ->
    nextAt += time
    wrapper.timeout = setTimeout wrapper, nextAt - new Date().getTime()
    fn()

  # Clear the next call when canceled.
  wrapper.cancel = -> clearTimeout wrapper.timeout

  # Schedule the first call.
  setTimeout wrapper, nextAt - new Date().getTime()

  # Return the wrapper function so cancel() can later be called on it.
  return wrapper

获得咖啡脚本并在这里JS：<一href=\"https://gist.github.com/1d99b3cd81d610ac7351\">https://gist.github.com/1d99b3cd81d610ac7351

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