@svta/common-media-library/dist/throughput/EwmaEstimator.js

A common library for media playback in JavaScript

import { getBandwidthBps } from '../utils/getBandwidthBps.js';
import { Ewma } from './Ewma.js';
/**
 * Exponential Weighted Moving Average (EWMA) throughput estimator based on 2 half-lives
 *
 * @group Throughput
 *
 * @beta
 */
export class EwmaEstimator {
    constructor(options) {
        this.slowEwma = new Ewma(options.slowHalfLife);
        this.fastEwma = new Ewma(options.fastHalfLife);
    }
    sample(sample) {
        // TODO: shaka
        // 1. If `sample.encodedBodySize` is less than `this.minBytes_`, don't do anything
        // TODO: dash.js
        // 1. If `sample.encodedBodySize` is NaN or Infinity, don't do anything
        // TODO: hls.js
        // 1. If `durationSeconds` is less than `this.minDelayMs_`, make it `this.minDelayMs_` (default is 50ms)
        const durationSeconds = sample.duration / 1000;
        const bandwidthBps = getBandwidthBps(sample);
        this.slowEwma.sample(durationSeconds, bandwidthBps);
        this.fastEwma.sample(durationSeconds, bandwidthBps);
    }
    getEstimate() {
        // TODO: shaka
        // 1. Returns `defaultEstimate` for this.totalBytes < `options.minTotalBytes`
        // 1.1. Returns `options.defaultBandwidthEstimate`
        // 1.2. or `navigator.connection.downlink * 1e6` if available
        // TODO: dash.js
        // 1. Returns `NaN` for this.totalDuration <= 0
        // 2. `Math.max` for latency calculation
        // TODO: hls.js
        // 1. Returns `defaultEstimate` for this.totalDuration < `this.minDuration`
        // 1.1. Returns `config.abrEwmaDefaultEstimate` (default: 500 kbps)
        return Math.min(this.fastEwma.getEstimate(), this.slowEwma.getEstimate());
    }
    canEstimate() {
        // TODO: shaka, `this.totalBytes >= options.minTotalBytes`
        // TODO: hls.js, `this.totalDuration >= this.minDuration`
        return true;
    }
}
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