Source: lib/media/time_ranges_utils.js

  1. /**
  2.  * @license
  3.  * Copyright 2016 Google Inc.
  4.  *
  5.  * Licensed under the Apache License, Version 2.0 (the "License");
  6.  * you may not use this file except in compliance with the License.
  7.  * You may obtain a copy of the License at
  8.  *
  9.  *     http://www.apache.org/licenses/LICENSE-2.0
  10.  *
  11.  * Unless required by applicable law or agreed to in writing, software
  12.  * distributed under the License is distributed on an "AS IS" BASIS,
  13.  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14.  * See the License for the specific language governing permissions and
  15.  * limitations under the License.
  16.  */
  18. goog.provide('shaka.media.TimeRangesUtils');
  21. /**
  22.  * @namespace shaka.media.TimeRangesUtils
  23.  * @summary A set of utility functions for dealing with TimeRanges objects.
  24.  */
  27. /**
  28.  * Gets the first timestamp in the buffer.
  29.  *
  30.  * @param {TimeRanges} b
  31.  * @return {?number} The first buffered timestamp, in seconds, if |buffered|
  32.  *   is non-empty; otherwise, return null.
  33.  */
  34. shaka.media.TimeRangesUtils.bufferStart = function(b) {
  35.   if (!b) return null;
  36.   // Workaround Safari bug: https://goo.gl/EDRCoZ
  37.   if (b.length == 1 && b.end(0) - b.start(0) < 1e-6) return null;
  38.   // Workaround Edge bug: https://goo.gl/BtxKgb
  39.   if (b.length == 1 && b.start(0) < 0) return 0;
  40.   return b.length ? b.start(0) : null;
  41. };
  44. /**
  45.  * Gets the last timestamp in the buffer.
  46.  *
  47.  * @param {TimeRanges} b
  48.  * @return {?number} The last buffered timestamp, in seconds, if |buffered|
  49.  *   is non-empty; otherwise, return null.
  50.  */
  51. shaka.media.TimeRangesUtils.bufferEnd = function(b) {
  52.   if (!b) return null;
  53.   // Workaround Safari bug: https://goo.gl/EDRCoZ
  54.   if (b.length == 1 && b.end(0) - b.start(0) < 1e-6) return null;
  55.   return b.length ? b.end(b.length - 1) : null;
  56. };
  59. /**
  60.  * Determines if the given time is inside a buffered range.  This includes gaps,
  61.  * meaning that if the playhead is in a gap, it is considered buffered. If there
  62.  * is a small gap between the playhead and buffer start, consider it as
  63.  * buffered.
  64.  *
  65.  * @param {TimeRanges} b
  66.  * @param {number} time Playhead time
  67.  * @param {number=} smallGapLimit Set in configuration
  68.  * @return {boolean}
  69.  */
  70. shaka.media.TimeRangesUtils.isBuffered = function(b, time, smallGapLimit = 0) {
  71.   if (!b || !b.length) return false;
  72.   // Workaround Safari bug: https://goo.gl/EDRCoZ
  73.   if (b.length == 1 && b.end(0) - b.start(0) < 1e-6) return false;
  75.   if (time > b.end(b.length - 1)) {
  76.     return false;
  77.   }
  78.   // Push the time forward by the gap limit so that it is more likely to be in
  79.   // the range.
  80.   return (time + smallGapLimit >= b.start(0));
  81. };
  84. /**
  85.  * Computes how far ahead of the given timestamp is buffered.  To provide smooth
  86.  * playback while jumping gaps, we don't include the gaps when calculating this.
  87.  * This only includes the amount of content that is buffered.
  88.  *
  89.  * @param {TimeRanges} b
  90.  * @param {number} time
  91.  * @return {number} The number of seconds buffered, in seconds, ahead of the
  92.  *   given time.
  93.  */
  94. shaka.media.TimeRangesUtils.bufferedAheadOf = function(b, time) {
  95.   if (!b || !b.length) return 0;
  96.   // Workaround Safari bug: https://goo.gl/EDRCoZ
  97.   if (b.length == 1 && b.end(0) - b.start(0) < 1e-6) return 0;
  99.   // NOTE: On IE11, buffered ranges may show appended data before the associated
  100.   // append operation is complete.
  102.   // We calculate the buffered amount by ONLY accounting for the content
  103.   // buffered (i.e. we ignore the times of the gaps).  We also buffer through
  104.   // all gaps.
  105.   // Therefore, we start at the end and add up all buffers until |time|.
  106.   let result = 0;
  107.   for (let i = b.length - 1; i >= 0 && b.end(i) > time; --i) {
  108.     result += b.end(i) - Math.max(b.start(i), time);
  109.   }
  111.   return result;
  112. };
  115. /**
  116.  * Determines if the given time is inside a gap between buffered ranges.  If it
  117.  * is, this returns the index of the buffer that is *ahead* of the gap.
  118.  *
  119.  * @param {TimeRanges} b
  120.  * @param {number} time
  121.  * @return {?number} The index of the buffer after the gap, or null if not in a
  122.  *   gap.
  123.  */
  124. shaka.media.TimeRangesUtils.getGapIndex = function(b, time) {
  125.   if (!b || !b.length) return null;
  126.   // Workaround Safari bug: https://goo.gl/EDRCoZ
  127.   if (b.length == 1 && b.end(0) - b.start(0) < 1e-6) return null;
  129.   // IE/Edge stops 0.5 seconds before a gap, so it needs a much larger
  130.   // threshold, but we don't want to punish other browsers that stop closer.
  131.   // See: https://goo.gl/cuAcYd
  132.   let threshold = 0.1;
  133.   if (/(Edge\/|Trident\/|Tizen|CrKey)/.test(navigator.userAgent)) {
  134.     threshold = 0.5;
  135.   }
  137.   for (let i = 0; i < b.length; i++) {
  138.     if (b.start(i) > time && (i == 0 || b.end(i - 1) - time <= threshold)) {
  139.       return i;
  140.     }
  141.   }
  143.   return null;
  144. };
  147. /**
  148.  * @param {TimeRanges} b
  149.  * @return {!Array.<shakaExtern.BufferedRange>}
  150.  */
  151. shaka.media.TimeRangesUtils.getBufferedInfo = function(b) {
  152.   if (!b) return [];
  153.   let ret = [];
  154.   for (let i = 0; i < b.length; i++) {
  155.     ret.push({start: b.start(i), end: b.end(i)});
  156.   }
  157.   return ret;
  158. };