Bug 189337

Note: I'm asking because I'm using a WKWebView in an iOS app, and it will randomly get killed (it turns blank) by the OS because it appearently uses too much memory.

<rdar://problem/44271160>

I wonder if WebAudio-related classes are not reporting their memory costs to GC correctly?

(In reply to Simon Fraser (smfr) from comment #3)
> I wonder if WebAudio-related classes are not reporting their memory costs to
> GC correctly?

AudioBuffer (which contains all the decoded audio data) implements memoryCost(), which should be what the GC uses to determine object size. I'm guessing that there's an AudioBufferSourceNode which is retaining the decoded AudioBuffer and that the ABSN is being kept alive long after its playback has completed.

(In reply to Jer Noble from comment #4)
> I'm
> guessing that there's an AudioBufferSourceNode which is retaining the
> decoded AudioBuffer and that the ABSN is being kept alive long after its
> playback has completed.

As I said, I do not play back the buffer. I just use it for generating an overview. Here's the complete code (it's Tea, our in-house programming language that transcompiles to JS, but I hope it's readable enough!)

HTTP.get("sevenapp:///#{encodeURIComponent(@playingPath)}", (audioData) =>
	if not audioData?
		@clearPeaks()
		<-
	Audio.context.decodeAudioData(audioData, (buffer) =>
		if not buffer?
			@clearPeaks()
			<-
		samples = buffer.getChannelData(0)
		# 30 samples per second
		step = buffer.sampleRate / 30
		@peaks[@playingPath] = peaks = []
		for frame in [0...samples.length/step]
			sum = 0
			for index in [frame*step...(frame+1)*step] by 256 # accuracy, higher = worse, 1 = best
				if index >= samples.length
					break
				sum += Math.abs(samples[Math.floor(index)])
			sum /= step/256
			peaks.push(sum)
		@renderPeaks()
	)
)

(In reply to ae from comment #5)
> (In reply to Jer Noble from comment #4)
> > I'm
> > guessing that there's an AudioBufferSourceNode which is retaining the
> > decoded AudioBuffer and that the ABSN is being kept alive long after its
> > playback has completed.
> 
> As I said, I do not play back the buffer. I just use it for generating an
> overview. Here's the complete code (it's Tea, our in-house programming
> language that transcompiles to JS, but I hope it's readable enough!)
> 
> HTTP.get("sevenapp:///#{encodeURIComponent(@playingPath)}", (audioData) =>
> 	if not audioData?
> 		@clearPeaks()
> 		<-
> 	Audio.context.decodeAudioData(audioData, (buffer) =>
> 		if not buffer?
> 			@clearPeaks()
> 			<-
> 		samples = buffer.getChannelData(0)

Unless your in-house transpiler adds scoping statements to these variables, your going to be setting window.samples to a large Float32Array.  If your in-house transpiler /is/ adding scoping statements, it would be much more useful to post the transpiled source.

(In reply to Jer Noble from comment #6)
> (In reply to ae from comment #5)
> > (In reply to Jer Noble from comment #4)
> > > I'm
> > > guessing that there's an AudioBufferSourceNode which is retaining the
> > > decoded AudioBuffer and that the ABSN is being kept alive long after its
> > > playback has completed.
> > 
> > As I said, I do not play back the buffer. I just use it for generating an
> > overview. Here's the complete code (it's Tea, our in-house programming
> > language that transcompiles to JS, but I hope it's readable enough!)
> > 
> > HTTP.get("sevenapp:///#{encodeURIComponent(@playingPath)}", (audioData) =>
> > 	if not audioData?
> > 		@clearPeaks()
> > 		<-
> > 	Audio.context.decodeAudioData(audioData, (buffer) =>
> > 		if not buffer?
> > 			@clearPeaks()
> > 			<-
> > 		samples = buffer.getChannelData(0)
> 
> Unless your in-house transpiler adds scoping statements to these variables,
> your going to be setting window.samples to a large Float32Array.  If your
> in-house transpiler /is/ adding scoping statements, it would be much more
> useful to post the transpiled source.


Oh sorry, of course it makes 'samples' local (var samples), I'm just so used to this that I forgot. Here's the transpiled code (not too readable):

    getPeaks: function() {
      element('player-peaks').classList.remove('show');
      if (this.peaks[this.playingPath] != null) {
        timer(0.5, (function(_this) {
          return function() {
            _this.renderPeaks();
          };
        })(this));
        return;
      }
      if (Audio.context == null) {
        this.needPeaksOnResume = true;
        return;
      }
      this.needPeaksOnResume = false;
      HTTP.get("sevenapp:///" + (encodeURIComponent(this.playingPath)), (function(_this) {
        return function(audioData) {
          if (audioData == null) {
            _this.clearPeaks();
            return;
          }
          Audio.context.decodeAudioData(audioData, function(buffer) {
            var frame, i, index, j, peaks, ref, ref1, ref2, samples, step, sum;
            if (buffer == null) {
              _this.clearPeaks();
              return;
            }
            samples = buffer.getChannelData(0);
            step = buffer.sampleRate / 30;
            _this.peaks[_this.playingPath] = peaks = [];
            for (frame = i = 0, ref = samples.length / step; 0 <= ref ? i < ref : i > ref; frame = 0 <= ref ? ++i : --i) {
              sum = 0;
              for (index = j = ref1 = frame * step, ref2 = (frame + 1) * step; j < ref2; index = j += 256) {
                if (index >= samples.length) {
                  break;
                }
                sum += Math.abs(samples[Math.floor(index)]);
              }
              sum /= step / 256;
              peaks.push(sum);
            }
            _this.renderPeaks();
          });
        };
      })(this));
    },