fps-controller.js

/*
 * FPS controller
 *
 */

 import Event                from '../events';
 import observer             from '../observer';
 import {logger}             from '../utils/logger';


 class FPSController {

  constructor(hls) {
    this.hls = hls;
    this.timer = setInterval(this.checkFPS, hls.config.fpsDroppedMonitoringPeriod);
  }

  destroy() {
    if(this.timer) {
     clearInterval(this.timer);
    }
  }
  checkFPS() {
    var v = this.hls.video;
    if(v) {
      var decodedFrames = v.webkitDecodedFrameCount, droppedFrames = v.webkitDroppedFrameCount,currentTime = new Date();
      if(decodedFrames) {
        if(this.lastTime) {
          var currentPeriod =  currentTime-this.lastTime;
          var currentDropped = droppedFrames - this.lastDroppedFrames;
          var currentDecoded = decodedFrames - this.lastDecodedFrames;
          var decodedFPS = 1000*currentDecoded/currentPeriod;
          var droppedFPS = 1000*currentDropped/currentPeriod;
          if(droppedFPS>0) {
            logger.log(`checkFPS : droppedFPS/decodedFPS:${droppedFPS.toFixed(1)}/${decodedFPS.toFixed(1)}`);
            if(currentDropped > this.hls.config.fpsDroppedMonitoringThreshold*currentDecoded) {
              logger.warn(`drop FPS ratio greater than max allowed value`);
              observer.trigger(Event.FPS_DROP,{ currentDropped : currentDropped, currentDecoded : currentDecoded, totalDroppedFrames : droppedFrames});
            }
          }
        }
        this.lastTime = currentTime;
        this.lastDroppedFrames=droppedFrames;
        this.lastDecodedFrames=decodedFrames;
      }
    }
  }
 }

export default FPSController;