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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 | 5x 5x 5x 5x 5x 5x 9x 9x 9x 9x 9x 10x 10x 10x 9x 1x | /*
* EWMA Bandwidth Estimator
* - heavily inspired from shaka-player
* Tracks bandwidth samples and estimates available bandwidth.
* Based on the minimum of two exponentially-weighted moving averages with
* different half-lives.
*/
import EWMA from '../utils/ewma';
class EwmaBandWidthEstimator {
constructor (hls, slow, fast, defaultEstimate) {
this.hls = hls;
this.defaultEstimate_ = defaultEstimate;
this.minWeight_ = 0.001;
this.minDelayMs_ = 50;
this.slow_ = new EWMA(slow);
this.fast_ = new EWMA(fast);
}
sample (durationMs, numBytes) {
durationMs = Math.max(durationMs, this.minDelayMs_);
let bandwidth = 8000 * numBytes / durationMs,
// console.log('instant bw:'+ Math.round(bandwidth));
// we weight sample using loading duration....
weight = durationMs / 1000;
this.fast_.sample(weight, bandwidth);
this.slow_.sample(weight, bandwidth);
}
canEstimate () {
let fast = this.fast_;
return (fast && fast.getTotalWeight() >= this.minWeight_);
}
getEstimate () {
if (this.canEstimate()) {
// console.log('slow estimate:'+ Math.round(this.slow_.getEstimate()));
// console.log('fast estimate:'+ Math.round(this.fast_.getEstimate()));
// Take the minimum of these two estimates. This should have the effect of
// adapting down quickly, but up more slowly.
return Math.min(this.fast_.getEstimate(), this.slow_.getEstimate());
} else {
return this.defaultEstimate_;
}
}
destroy () {
}
}
export default EwmaBandWidthEstimator;
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