shaka-player/lib/polyfill/videoplaybackquality.js

/**
 * @license
 * Copyright 2016 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

goog.provide('shaka.polyfill.VideoPlaybackQuality');

goog.require('shaka.polyfill.register');


/**
 * @namespace shaka.polyfill.VideoPlaybackQuality
 *
 * @summary A polyfill to provide MSE VideoPlaybackQuality metrics.
 * Many browsers do not yet provide this API, and Chrome currently provides
 * similar data through individual prefixed attributes on HTMLVideoElement.
 */


/**
 * Install the polyfill if needed.
 */
shaka.polyfill.VideoPlaybackQuality.install = function() {
  if (!window.HTMLVideoElement) {
    // Avoid errors on very old browsers.
    return;
  }

  var proto = HTMLVideoElement.prototype;
  if (proto.getVideoPlaybackQuality) {
    // No polyfill needed.
    return;
  }

  if ('webkitDroppedFrameCount' in proto) {
    proto.getVideoPlaybackQuality =
        shaka.polyfill.VideoPlaybackQuality.webkit_;
  }
};


/**
 * @this {HTMLVideoElement}
 * @return {!VideoPlaybackQuality}
 * @private
 */
shaka.polyfill.VideoPlaybackQuality.webkit_ = function() {
  return {
    'droppedVideoFrames': this.webkitDroppedFrameCount,
    'totalVideoFrames': this.webkitDecodedFrameCount,
    // Not provided by this polyfill:
    'corruptedVideoFrames': 0,
    'creationTime': NaN,
    'totalFrameDelay': 0
  };
};


shaka.polyfill.register(shaka.polyfill.VideoPlaybackQuality.install);