85 lines
2.4 KiB
JavaScript
85 lines
2.4 KiB
JavaScript
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/*
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* simple ABR Controller
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*/
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import Event from '../events';
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class AbrController {
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constructor(hls) {
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this.hls = hls;
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this.lastfetchlevel = 0;
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this._autoLevelCapping = -1;
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this._nextAutoLevel = -1;
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this.onflp = this.onFragmentLoadProgress.bind(this);
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hls.on(Event.FRAG_LOAD_PROGRESS, this.onflp);
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}
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destroy() {
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this.hls.off(Event.FRAG_LOAD_PROGRESS, this.onflp);
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}
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onFragmentLoadProgress(event, data) {
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var stats = data.stats;
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if (stats.aborted === undefined) {
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this.lastfetchduration = (performance.now() - stats.trequest) / 1000;
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this.lastfetchlevel = data.frag.level;
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this.lastbw = (stats.loaded * 8) / this.lastfetchduration;
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//console.log(`fetchDuration:${this.lastfetchduration},bw:${(this.lastbw/1000).toFixed(0)}/${stats.aborted}`);
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}
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}
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/** Return the capping/max level value that could be used by automatic level selection algorithm **/
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get autoLevelCapping() {
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return this._autoLevelCapping;
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}
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/** set the capping/max level value that could be used by automatic level selection algorithm **/
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set autoLevelCapping(newLevel) {
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this._autoLevelCapping = newLevel;
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}
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get nextAutoLevel() {
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var lastbw = this.lastbw, hls = this.hls,adjustedbw, i, maxAutoLevel;
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if (this._autoLevelCapping === -1) {
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maxAutoLevel = hls.levels.length - 1;
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} else {
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maxAutoLevel = this._autoLevelCapping;
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}
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if (this._nextAutoLevel !== -1) {
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var nextLevel = Math.min(this._nextAutoLevel,maxAutoLevel);
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if (nextLevel === this.lastfetchlevel) {
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this._nextAutoLevel = -1;
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} else {
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return nextLevel;
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}
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}
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// follow algorithm captured from stagefright :
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// https://android.googlesource.com/platform/frameworks/av/+/master/media/libstagefright/httplive/LiveSession.cpp
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// Pick the highest bandwidth stream below or equal to estimated bandwidth.
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for (i = 0; i <= maxAutoLevel; i++) {
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// consider only 80% of the available bandwidth, but if we are switching up,
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// be even more conservative (70%) to avoid overestimating and immediately
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// switching back.
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if (i <= this.lastfetchlevel) {
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adjustedbw = 0.8 * lastbw;
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} else {
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adjustedbw = 0.7 * lastbw;
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}
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if (adjustedbw < hls.levels[i].bitrate) {
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return Math.max(0, i - 1);
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}
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}
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return i - 1;
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}
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set nextAutoLevel(nextLevel) {
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this._nextAutoLevel = nextLevel;
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}
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}
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export default AbrController;
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