Sketch JS，如何在音频标签上使用AWS预签名URL？

Question

Quick look

I'm using Sketch.js plugin in this example. I would like to use my pre-signed urls as well but they don't work. Expiration time is set long enough (1 day) so there's something wrong with the JS itself.

I have an S3 bucket where I store some music public protected. Using the official AWS SDK I can generate urls like:

https://d225******.cloudfront.net/song.m4a?Expires=1493381986&Signature=***&Key-Pair-Id=***

I'm using pre-signed urls over my website without any problem, but in this script won't work:

<script>
var ALPHA, AudioAnalyser, COLORS, MP3_PATH, NUM_BANDS, NUM_PARTICLES, Particle, SCALE, SIZE, SMOOTHING, SPEED, SPIN;

MP3_PATH = 'my_presigned_url';

AudioAnalyser = (function() {
  AudioAnalyser.AudioContext = self.AudioContext || self.webkitAudioContext;

  AudioAnalyser.enabled = AudioAnalyser.AudioContext != null;

  function AudioAnalyser(audio, numBands, smoothing) {
    var src;
    this.audio = audio != null ? audio : new Audio();
    this.numBands = numBands != null ? numBands : 256;
    this.smoothing = smoothing != null ? smoothing : 0.3;
    if (typeof this.audio === 'string') {
      src = this.audio;
      this.audio = new Audio();
      this.audio.crossOrigin = "anonymous";
      this.audio.controls = true;
      this.audio.src = src;
    }
    this.context = new AudioAnalyser.AudioContext();
    this.jsNode = this.context.createScriptProcessor(2048, 1, 1);
    this.analyser = this.context.createAnalyser();
    this.analyser.smoothingTimeConstant = this.smoothing;
    this.analyser.fftSize = this.numBands * 2;
    this.bands = new Uint8Array(this.analyser.frequencyBinCount);
    this.audio.addEventListener('canplay', (function(_this) {
      return function() {
        _this.source = _this.context.createMediaElementSource(_this.audio);
        _this.source.connect(_this.analyser);
        _this.analyser.connect(_this.jsNode);
        _this.jsNode.connect(_this.context.destination);
        _this.source.connect(_this.context.destination);
        return _this.jsNode.onaudioprocess = function() {
          _this.analyser.getByteFrequencyData(_this.bands);
          if (!_this.audio.paused) {
            return typeof _this.onUpdate === "function" ? _this.onUpdate(_this.bands) : void 0;
          }
        };
      };
    })(this));

  }

  AudioAnalyser.prototype.start = function() {
    return this.audio.play();
  };

  AudioAnalyser.prototype.stop = function() {
    return this.audio.pause();
  };

  return AudioAnalyser;

})();

Sketch.create({
  particles: [],
  setup: function() {
    var analyser, error, i, intro, j, particle, ref, warning, x, y;
    for (i = j = 0, ref = NUM_PARTICLES - 1; j <= ref; i = j += 1) {
      x = random(this.width);
      y = random(this.height * 2);
      particle = new Particle(x, y);
      particle.energy = random(particle.band / 256);
      this.particles.push(particle);
    }
    if (AudioAnalyser.enabled) {
      try {
        analyser = new AudioAnalyser(MP3_PATH, NUM_BANDS, SMOOTHING);
        analyser.onUpdate = (function(_this) {
          return function(bands) {
            var k, len, ref1, results;
            ref1 = _this.particles;
            results = [];
            for (k = 0, len = ref1.length; k < len; k++) {
              particle = ref1[k];
              results.push(particle.energy = bands[particle.band] / 256);
            }
            return results;
          };
        })(this);
        analyser.start();
        document.getElementById('player-container').appendChild(analyser.audio);
        document.getElementsByTagName("audio")[0].setAttribute("id", "dy_wowaudio"); 
        intro = document.getElementById('intro');
        intro.style.display = 'none';
      } catch (_error) {
        error = _error;
      }
    }
  }
});
// generated by coffee-script 1.9.2
</script>

The script works fine (as you can see in the example above) without a pre-signed url, so what can I do to use my pre-signed urls inside AudioAnalyser function ?

Answer 1

I've seen html5 video tags make multiple requests. I assume to fetch some meta-data like play length and the first frame of video to use as a thumbnail. You might try playing with the preload attribute to prevent this.

Specifically, if the clip is small, preload="auto" might be everything you need. If the browser has to make follow requests you're gonna have a hard time I think. Here's some relevant info

Another way to go about this that I think may work more reliably is to generate temporary credentials as needed.

See the docs for more on this: - Requesting temp creds - Accessing resources with temp creds

Combined with a JS package for signing AWS requests like binoculars/aws-sigv4 or copy someone else who's doing this in-browser.

Answer 2

Share your browser error message if any. It may by problem related to cross origin for S3 bucket data.