cap-level-controller.js

/*
 * cap stream level to media size dimension controller
*/

import Event from '../events';
import EventHandler from '../event-handler';

class CapLevelController extends EventHandler {
	constructor(hls) {
    super(hls,
      Event.FPS_DROP_LEVEL_CAPPING,
      Event.MEDIA_ATTACHING,
      Event.MANIFEST_PARSED);
	}

	destroy() {
    if (this.hls.config.capLevelToPlayerSize) {
      this.media = this.restrictedLevels = null;
      this.autoLevelCapping = Number.POSITIVE_INFINITY;
      if (this.timer) {
        this.timer = clearInterval(this.timer);
      }
    }
  }

  onFpsDropLevelCapping(data) {
    if (!this.restrictedLevels) {
      this.restrictedLevels = [];
    }
    if (!this.isLevelRestricted(data.droppedLevel)) {
      this.restrictedLevels.push(data.droppedLevel);
    }
  }

	onMediaAttaching(data) {
    this.media = data.media instanceof HTMLVideoElement ? data.media : null;
  }

  onManifestParsed(data) {
    const hls = this.hls;
    if (hls.config.capLevelToPlayerSize) {
      this.autoLevelCapping = Number.POSITIVE_INFINITY;
      this.levels = data.levels;
      hls.firstLevel = this.getMaxLevel(data.firstLevel);
      clearInterval(this.timer);
      this.timer = setInterval(this.detectPlayerSize.bind(this), 1000);
      this.detectPlayerSize();
    }
  }

  detectPlayerSize() {
    if (this.media) {
      let levelsLength = this.levels ? this.levels.length : 0;
      if (levelsLength) {
        const hls = this.hls;
        hls.autoLevelCapping = this.getMaxLevel(levelsLength - 1);
        if (hls.autoLevelCapping > this.autoLevelCapping) {
          // if auto level capping has a higher value for the previous one, flush the buffer using nextLevelSwitch
          // usually happen when the user go to the fullscreen mode.
          hls.streamController.nextLevelSwitch();
        }
        this.autoLevelCapping = hls.autoLevelCapping;
      }
    }
  }

  /*
  * returns level should be the one with the dimensions equal or greater than the media (player) dimensions (so the video will be downscaled)
  */
  getMaxLevel(capLevelIndex) {
    let result = 0,
        i,
        level,
        mWidth = this.mediaWidth,
        mHeight = this.mediaHeight,
        lWidth = 0,
        lHeight = 0;

    for (i = 0; i <= capLevelIndex; i++) {
      level = this.levels[i];
      if (this.isLevelRestricted(i)) {
        break;
      }
      result = i;
      lWidth = level.width;
      lHeight = level.height;
      if (mWidth <= lWidth || mHeight <= lHeight) {
        break;
      }
    }
    return result;
  }

  isLevelRestricted(level) {
    return (this.restrictedLevels && this.restrictedLevels.indexOf(level) !== -1) ? true : false;
  }

  get contentScaleFactor() {
    let pixelRatio = 1;
    try {
      pixelRatio =  window.devicePixelRatio;
    } catch(e) {}
    return pixelRatio;
  }

  get mediaWidth() {
    let width;
    const media = this.media;
    if (media) {
      width = media.width || media.clientWidth || media.offsetWidth;
      width *= this.contentScaleFactor;
    }
    return width;
  }

  get mediaHeight() {
    let height;
    const media = this.media;
    if (media) {
      height = media.height || media.clientHeight || media.offsetHeight;
      height *= this.contentScaleFactor;
    }
    return height;
  }
}

export default CapLevelController;