First release

node_modules/@videojs/http-streaming/src/playlist-selectors.js

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+import window from 'global/window';
+import Config from './config';
+import Playlist from './playlist';
+import { codecsForPlaylist } from './util/codecs.js';
+import logger from './util/logger';
+
+const logFn = logger('PlaylistSelector');
+const representationToString = function(representation) {
+  if (!representation || !representation.playlist) {
+    return;
+  }
+  const playlist = representation.playlist;
+
+  return JSON.stringify({
+    id: playlist.id,
+    bandwidth: representation.bandwidth,
+    width: representation.width,
+    height: representation.height,
+    codecs: playlist.attributes && playlist.attributes.CODECS || ''
+  });
+};
+
+// Utilities
+
+/**
+ * Returns the CSS value for the specified property on an element
+ * using `getComputedStyle`. Firefox has a long-standing issue where
+ * getComputedStyle() may return null when running in an iframe with
+ * `display: none`.
+ *
+ * @see https://bugzilla.mozilla.org/show_bug.cgi?id=548397
+ * @param {HTMLElement} el the htmlelement to work on
+ * @param {string} the proprety to get the style for
+ */
+const safeGetComputedStyle = function(el, property) {
+  if (!el) {
+    return '';
+  }
+
+  const result = window.getComputedStyle(el);
+
+  if (!result) {
+    return '';
+  }
+
+  return result[property];
+};
+
+/**
+ * Resuable stable sort function
+ *
+ * @param {Playlists} array
+ * @param {Function} sortFn Different comparators
+ * @function stableSort
+ */
+const stableSort = function(array, sortFn) {
+  const newArray = array.slice();
+
+  array.sort(function(left, right) {
+    const cmp = sortFn(left, right);
+
+    if (cmp === 0) {
+      return newArray.indexOf(left) - newArray.indexOf(right);
+    }
+    return cmp;
+  });
+};
+
+/**
+ * A comparator function to sort two playlist object by bandwidth.
+ *
+ * @param {Object} left a media playlist object
+ * @param {Object} right a media playlist object
+ * @return {number} Greater than zero if the bandwidth attribute of
+ * left is greater than the corresponding attribute of right. Less
+ * than zero if the bandwidth of right is greater than left and
+ * exactly zero if the two are equal.
+ */
+export const comparePlaylistBandwidth = function(left, right) {
+  let leftBandwidth;
+  let rightBandwidth;
+
+  if (left.attributes.BANDWIDTH) {
+    leftBandwidth = left.attributes.BANDWIDTH;
+  }
+  leftBandwidth = leftBandwidth || window.Number.MAX_VALUE;
+  if (right.attributes.BANDWIDTH) {
+    rightBandwidth = right.attributes.BANDWIDTH;
+  }
+  rightBandwidth = rightBandwidth || window.Number.MAX_VALUE;
+
+  return leftBandwidth - rightBandwidth;
+};
+
+/**
+ * A comparator function to sort two playlist object by resolution (width).
+ *
+ * @param {Object} left a media playlist object
+ * @param {Object} right a media playlist object
+ * @return {number} Greater than zero if the resolution.width attribute of
+ * left is greater than the corresponding attribute of right. Less
+ * than zero if the resolution.width of right is greater than left and
+ * exactly zero if the two are equal.
+ */
+export const comparePlaylistResolution = function(left, right) {
+  let leftWidth;
+  let rightWidth;
+
+  if (left.attributes.RESOLUTION &&
+      left.attributes.RESOLUTION.width) {
+    leftWidth = left.attributes.RESOLUTION.width;
+  }
+
+  leftWidth = leftWidth || window.Number.MAX_VALUE;
+
+  if (right.attributes.RESOLUTION &&
+      right.attributes.RESOLUTION.width) {
+    rightWidth = right.attributes.RESOLUTION.width;
+  }
+
+  rightWidth = rightWidth || window.Number.MAX_VALUE;
+
+  // NOTE - Fallback to bandwidth sort as appropriate in cases where multiple renditions
+  // have the same media dimensions/ resolution
+  if (leftWidth === rightWidth &&
+      left.attributes.BANDWIDTH &&
+      right.attributes.BANDWIDTH) {
+    return left.attributes.BANDWIDTH - right.attributes.BANDWIDTH;
+  }
+  return leftWidth - rightWidth;
+};
+
+/**
+ * Chooses the appropriate media playlist based on bandwidth and player size
+ *
+ * @param {Object} master
+ *        Object representation of the master manifest
+ * @param {number} playerBandwidth
+ *        Current calculated bandwidth of the player
+ * @param {number} playerWidth
+ *        Current width of the player element (should account for the device pixel ratio)
+ * @param {number} playerHeight
+ *        Current height of the player element (should account for the device pixel ratio)
+ * @param {boolean} limitRenditionByPlayerDimensions
+ *        True if the player width and height should be used during the selection, false otherwise
+ * @param {Object} masterPlaylistController
+ *        the current masterPlaylistController object
+ * @return {Playlist} the highest bitrate playlist less than the
+ * currently detected bandwidth, accounting for some amount of
+ * bandwidth variance
+ */
+export let simpleSelector = function(
+  master,
+  playerBandwidth,
+  playerWidth,
+  playerHeight,
+  limitRenditionByPlayerDimensions,
+  masterPlaylistController
+) {
+
+  // If we end up getting called before `master` is available, exit early
+  if (!master) {
+    return;
+  }
+
+  const options = {
+    bandwidth: playerBandwidth,
+    width: playerWidth,
+    height: playerHeight,
+    limitRenditionByPlayerDimensions
+  };
+
+  let playlists = master.playlists;
+
+  // if playlist is audio only, select between currently active audio group playlists.
+  if (Playlist.isAudioOnly(master)) {
+    playlists = masterPlaylistController.getAudioTrackPlaylists_();
+    // add audioOnly to options so that we log audioOnly: true
+    // at the buttom of this function for debugging.
+    options.audioOnly = true;
+  }
+  // convert the playlists to an intermediary representation to make comparisons easier
+  let sortedPlaylistReps = playlists.map((playlist) => {
+    let bandwidth;
+    const width = playlist.attributes && playlist.attributes.RESOLUTION && playlist.attributes.RESOLUTION.width;
+    const height = playlist.attributes && playlist.attributes.RESOLUTION && playlist.attributes.RESOLUTION.height;
+
+    bandwidth = playlist.attributes && playlist.attributes.BANDWIDTH;
+
+    bandwidth = bandwidth || window.Number.MAX_VALUE;
+
+    return {
+      bandwidth,
+      width,
+      height,
+      playlist
+    };
+  });
+
+  stableSort(sortedPlaylistReps, (left, right) => left.bandwidth - right.bandwidth);
+
+  // filter out any playlists that have been excluded due to
+  // incompatible configurations
+  sortedPlaylistReps = sortedPlaylistReps.filter((rep) => !Playlist.isIncompatible(rep.playlist));
+
+  // filter out any playlists that have been disabled manually through the representations
+  // api or blacklisted temporarily due to playback errors.
+  let enabledPlaylistReps = sortedPlaylistReps.filter((rep) => Playlist.isEnabled(rep.playlist));
+
+  if (!enabledPlaylistReps.length) {
+    // if there are no enabled playlists, then they have all been blacklisted or disabled
+    // by the user through the representations api. In this case, ignore blacklisting and
+    // fallback to what the user wants by using playlists the user has not disabled.
+    enabledPlaylistReps = sortedPlaylistReps.filter((rep) => !Playlist.isDisabled(rep.playlist));
+  }
+
+  // filter out any variant that has greater effective bitrate
+  // than the current estimated bandwidth
+  const bandwidthPlaylistReps = enabledPlaylistReps.filter((rep) => rep.bandwidth * Config.BANDWIDTH_VARIANCE < playerBandwidth);
+
+  let highestRemainingBandwidthRep =
+    bandwidthPlaylistReps[bandwidthPlaylistReps.length - 1];
+
+  // get all of the renditions with the same (highest) bandwidth
+  // and then taking the very first element
+  const bandwidthBestRep = bandwidthPlaylistReps.filter((rep) => rep.bandwidth === highestRemainingBandwidthRep.bandwidth)[0];
+
+  // if we're not going to limit renditions by player size, make an early decision.
+  if (limitRenditionByPlayerDimensions === false) {
+    const chosenRep = (
+      bandwidthBestRep ||
+      enabledPlaylistReps[0] ||
+      sortedPlaylistReps[0]
+    );
+
+    if (chosenRep && chosenRep.playlist) {
+      let type = 'sortedPlaylistReps';
+
+      if (bandwidthBestRep) {
+        type = 'bandwidthBestRep';
+      }
+      if (enabledPlaylistReps[0]) {
+        type = 'enabledPlaylistReps';
+      }
+      logFn(`choosing ${representationToString(chosenRep)} using ${type} with options`, options);
+
+      return chosenRep.playlist;
+    }
+
+    logFn('could not choose a playlist with options', options);
+    return null;
+  }
+
+  // filter out playlists without resolution information
+  const haveResolution = bandwidthPlaylistReps.filter((rep) => rep.width && rep.height);
+
+  // sort variants by resolution
+  stableSort(haveResolution, (left, right) => left.width - right.width);
+
+  // if we have the exact resolution as the player use it
+  const resolutionBestRepList = haveResolution.filter((rep) => rep.width === playerWidth && rep.height === playerHeight);
+
+  highestRemainingBandwidthRep = resolutionBestRepList[resolutionBestRepList.length - 1];
+  // ensure that we pick the highest bandwidth variant that have exact resolution
+  const resolutionBestRep = resolutionBestRepList.filter((rep) => rep.bandwidth === highestRemainingBandwidthRep.bandwidth)[0];
+
+  let resolutionPlusOneList;
+  let resolutionPlusOneSmallest;
+  let resolutionPlusOneRep;
+
+  // find the smallest variant that is larger than the player
+  // if there is no match of exact resolution
+  if (!resolutionBestRep) {
+    resolutionPlusOneList = haveResolution.filter((rep) => rep.width > playerWidth || rep.height > playerHeight);
+
+    // find all the variants have the same smallest resolution
+    resolutionPlusOneSmallest = resolutionPlusOneList.filter((rep) => rep.width === resolutionPlusOneList[0].width &&
+               rep.height === resolutionPlusOneList[0].height);
+
+    // ensure that we also pick the highest bandwidth variant that
+    // is just-larger-than the video player
+    highestRemainingBandwidthRep =
+      resolutionPlusOneSmallest[resolutionPlusOneSmallest.length - 1];
+    resolutionPlusOneRep = resolutionPlusOneSmallest.filter((rep) => rep.bandwidth === highestRemainingBandwidthRep.bandwidth)[0];
+  }
+
+  // fallback chain of variants
+  const chosenRep = (
+    resolutionPlusOneRep ||
+    resolutionBestRep ||
+    bandwidthBestRep ||
+    enabledPlaylistReps[0] ||
+    sortedPlaylistReps[0]
+  );
+
+  if (chosenRep && chosenRep.playlist) {
+    let type = 'sortedPlaylistReps';
+
+    if (resolutionPlusOneRep) {
+      type = 'resolutionPlusOneRep';
+    } else if (resolutionBestRep) {
+      type = 'resolutionBestRep';
+    } else if (bandwidthBestRep) {
+      type = 'bandwidthBestRep';
+    } else if (enabledPlaylistReps[0]) {
+      type = 'enabledPlaylistReps';
+    }
+
+    logFn(`choosing ${representationToString(chosenRep)} using ${type} with options`, options);
+    return chosenRep.playlist;
+  }
+  logFn('could not choose a playlist with options', options);
+  return null;
+};
+
+export const TEST_ONLY_SIMPLE_SELECTOR = (newSimpleSelector) => {
+  const oldSimpleSelector = simpleSelector;
+
+  simpleSelector = newSimpleSelector;
+
+  return function resetSimpleSelector() {
+    simpleSelector = oldSimpleSelector;
+  };
+};
+
+// Playlist Selectors
+
+/**
+ * Chooses the appropriate media playlist based on the most recent
+ * bandwidth estimate and the player size.
+ *
+ * Expects to be called within the context of an instance of VhsHandler
+ *
+ * @return {Playlist} the highest bitrate playlist less than the
+ * currently detected bandwidth, accounting for some amount of
+ * bandwidth variance
+ */
+export const lastBandwidthSelector = function() {
+  const pixelRatio = this.useDevicePixelRatio ? window.devicePixelRatio || 1 : 1;
+
+  return simpleSelector(
+    this.playlists.master,
+    this.systemBandwidth,
+    parseInt(safeGetComputedStyle(this.tech_.el(), 'width'), 10) * pixelRatio,
+    parseInt(safeGetComputedStyle(this.tech_.el(), 'height'), 10) * pixelRatio,
+    this.limitRenditionByPlayerDimensions,
+    this.masterPlaylistController_
+  );
+};
+
+/**
+ * Chooses the appropriate media playlist based on an
+ * exponential-weighted moving average of the bandwidth after
+ * filtering for player size.
+ *
+ * Expects to be called within the context of an instance of VhsHandler
+ *
+ * @param {number} decay - a number between 0 and 1. Higher values of
+ * this parameter will cause previous bandwidth estimates to lose
+ * significance more quickly.
+ * @return {Function} a function which can be invoked to create a new
+ * playlist selector function.
+ * @see https://en.wikipedia.org/wiki/Moving_average#Exponential_moving_average
+ */
+export const movingAverageBandwidthSelector = function(decay) {
+  let average = -1;
+  let lastSystemBandwidth = -1;
+
+  if (decay < 0 || decay > 1) {
+    throw new Error('Moving average bandwidth decay must be between 0 and 1.');
+  }
+
+  return function() {
+    const pixelRatio = this.useDevicePixelRatio ? window.devicePixelRatio || 1 : 1;
+
+    if (average < 0) {
+      average = this.systemBandwidth;
+      lastSystemBandwidth = this.systemBandwidth;
+    }
+
+    // stop the average value from decaying for every 250ms
+    // when the systemBandwidth is constant
+    // and
+    // stop average from setting to a very low value when the
+    // systemBandwidth becomes 0 in case of chunk cancellation
+
+    if (this.systemBandwidth > 0 && this.systemBandwidth !== lastSystemBandwidth) {
+      average = decay * this.systemBandwidth + (1 - decay) * average;
+      lastSystemBandwidth = this.systemBandwidth;
+    }
+
+    return simpleSelector(
+      this.playlists.master,
+      average,
+      parseInt(safeGetComputedStyle(this.tech_.el(), 'width'), 10) * pixelRatio,
+      parseInt(safeGetComputedStyle(this.tech_.el(), 'height'), 10) * pixelRatio,
+      this.limitRenditionByPlayerDimensions,
+      this.masterPlaylistController_
+    );
+  };
+};
+
+/**
+ * Chooses the appropriate media playlist based on the potential to rebuffer
+ *
+ * @param {Object} settings
+ *        Object of information required to use this selector
+ * @param {Object} settings.master
+ *        Object representation of the master manifest
+ * @param {number} settings.currentTime
+ *        The current time of the player
+ * @param {number} settings.bandwidth
+ *        Current measured bandwidth
+ * @param {number} settings.duration
+ *        Duration of the media
+ * @param {number} settings.segmentDuration
+ *        Segment duration to be used in round trip time calculations
+ * @param {number} settings.timeUntilRebuffer
+ *        Time left in seconds until the player has to rebuffer
+ * @param {number} settings.currentTimeline
+ *        The current timeline segments are being loaded from
+ * @param {SyncController} settings.syncController
+ *        SyncController for determining if we have a sync point for a given playlist
+ * @return {Object|null}
+ *         {Object} return.playlist
+ *         The highest bandwidth playlist with the least amount of rebuffering
+ *         {Number} return.rebufferingImpact
+ *         The amount of time in seconds switching to this playlist will rebuffer. A
+ *         negative value means that switching will cause zero rebuffering.
+ */
+export const minRebufferMaxBandwidthSelector = function(settings) {
+  const {
+    master,
+    currentTime,
+    bandwidth,
+    duration,
+    segmentDuration,
+    timeUntilRebuffer,
+    currentTimeline,
+    syncController
+  } = settings;
+
+  // filter out any playlists that have been excluded due to
+  // incompatible configurations
+  const compatiblePlaylists = master.playlists.filter(playlist => !Playlist.isIncompatible(playlist));
+
+  // filter out any playlists that have been disabled manually through the representations
+  // api or blacklisted temporarily due to playback errors.
+  let enabledPlaylists = compatiblePlaylists.filter(Playlist.isEnabled);
+
+  if (!enabledPlaylists.length) {
+    // if there are no enabled playlists, then they have all been blacklisted or disabled
+    // by the user through the representations api. In this case, ignore blacklisting and
+    // fallback to what the user wants by using playlists the user has not disabled.
+    enabledPlaylists = compatiblePlaylists.filter(playlist => !Playlist.isDisabled(playlist));
+  }
+
+  const bandwidthPlaylists =
+    enabledPlaylists.filter(Playlist.hasAttribute.bind(null, 'BANDWIDTH'));
+
+  const rebufferingEstimates = bandwidthPlaylists.map((playlist) => {
+    const syncPoint = syncController.getSyncPoint(
+      playlist,
+      duration,
+      currentTimeline,
+      currentTime
+    );
+    // If there is no sync point for this playlist, switching to it will require a
+    // sync request first. This will double the request time
+    const numRequests = syncPoint ? 1 : 2;
+    const requestTimeEstimate = Playlist.estimateSegmentRequestTime(
+      segmentDuration,
+      bandwidth,
+      playlist
+    );
+    const rebufferingImpact = (requestTimeEstimate * numRequests) - timeUntilRebuffer;
+
+    return {
+      playlist,
+      rebufferingImpact
+    };
+  });
+
+  const noRebufferingPlaylists = rebufferingEstimates.filter((estimate) => estimate.rebufferingImpact <= 0);
+
+  // Sort by bandwidth DESC
+  stableSort(
+    noRebufferingPlaylists,
+    (a, b) => comparePlaylistBandwidth(b.playlist, a.playlist)
+  );
+
+  if (noRebufferingPlaylists.length) {
+    return noRebufferingPlaylists[0];
+  }
+
+  stableSort(rebufferingEstimates, (a, b) => a.rebufferingImpact - b.rebufferingImpact);
+
+  return rebufferingEstimates[0] || null;
+};
+
+/**
+ * Chooses the appropriate media playlist, which in this case is the lowest bitrate
+ * one with video.  If no renditions with video exist, return the lowest audio rendition.
+ *
+ * Expects to be called within the context of an instance of VhsHandler
+ *
+ * @return {Object|null}
+ *         {Object} return.playlist
+ *         The lowest bitrate playlist that contains a video codec.  If no such rendition
+ *         exists pick the lowest audio rendition.
+ */
+export const lowestBitrateCompatibleVariantSelector = function() {
+  // filter out any playlists that have been excluded due to
+  // incompatible configurations or playback errors
+  const playlists = this.playlists.master.playlists.filter(Playlist.isEnabled);
+
+  // Sort ascending by bitrate
+  stableSort(
+    playlists,
+    (a, b) => comparePlaylistBandwidth(a, b)
+  );
+
+  // Parse and assume that playlists with no video codec have no video
+  // (this is not necessarily true, although it is generally true).
+  //
+  // If an entire manifest has no valid videos everything will get filtered
+  // out.
+  const playlistsWithVideo = playlists.filter(playlist => !!codecsForPlaylist(this.playlists.master, playlist).video);
+
+  return playlistsWithVideo[0] || null;
+};