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@ -1,16 +1,15 @@ |
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/** |
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* playlist-loader |
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* |
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* A state machine that manages the loading, caching, and updating of |
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* M3U8 playlists. When tracking a live playlist, loaders will keep |
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* track of the duration of content that expired since the loader was |
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* initialized and when the current discontinuity sequence was |
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* encountered. A complete media timeline for a live playlist with |
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* expiring segments and discontinuities looks like this: |
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* expiring segments looks like this: |
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* |
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* |-- expiredPreDiscontinuity --|-- expiredPostDiscontinuity --|-- segments --| |
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* |-- expired --|-- segments --| |
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* |
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* You can use these values to calculate how much time has elapsed |
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* since the stream began loading or how long it has been since the |
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* most recent discontinuity was encountered, for instance. |
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*/ |
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(function(window, videojs) { |
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'use strict'; |
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@ -159,20 +158,13 @@ |
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// initialize the loader state
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loader.state = 'HAVE_NOTHING'; |
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// the total duration of all segments that expired and have been
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// removed from the current playlist after the last
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// #EXT-X-DISCONTINUITY. In a live playlist without
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// discontinuities, this is the total amount of time that has
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// been removed from the stream since the playlist loader began
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// The total duration of all segments that expired and have been
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// removed from the current playlist, in seconds. This property
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// should always be zero for non-live playlists. In a live
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// playlist, this is the total amount of time that has been
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// removed from the stream since the playlist loader began
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// tracking it.
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loader.expiredPostDiscontinuity_ = 0; |
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// the total duration of all segments that expired and have been
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// removed from the current playlist before the last
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// #EXT-X-DISCONTINUITY. The total amount of time that has
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// expired is always the sum of expiredPreDiscontinuity_ and
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// expiredPostDiscontinuity_.
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loader.expiredPreDiscontinuity_ = 0; |
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loader.expired_ = 0; |
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// capture the prototype dispose function
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dispose = this.dispose; |
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@ -364,41 +356,42 @@ |
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* @param update {object} the updated media playlist object |
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*/ |
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PlaylistLoader.prototype.updateMediaPlaylist_ = function(update) { |
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var lastDiscontinuity, expiredCount, i; |
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var expiredCount; |
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if (this.media_) { |
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expiredCount = update.mediaSequence - this.media_.mediaSequence; |
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// setup the index for duration calculations so that the newly
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// expired time will be accumulated after the last
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// discontinuity, unless we discover otherwise
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lastDiscontinuity = this.media_.mediaSequence; |
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if (this.media_.discontinuitySequence !== update.discontinuitySequence) { |
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i = expiredCount; |
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while (i--) { |
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if (this.media_.segments[i].discontinuity) { |
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// a segment that begins a new discontinuity sequence has expired
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lastDiscontinuity = i + this.media_.mediaSequence; |
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this.expiredPreDiscontinuity_ += this.expiredPostDiscontinuity_; |
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this.expiredPostDiscontinuity_ = 0; |
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break; |
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} |
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} |
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} |
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// update the expirated durations
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this.expiredPreDiscontinuity_ += Playlist.duration(this.media_, |
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this.media_.mediaSequence, |
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lastDiscontinuity); |
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this.expiredPostDiscontinuity_ += Playlist.duration(this.media_, |
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lastDiscontinuity, |
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update.mediaSequence); |
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// update the expired time count
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this.expired_ += Playlist.duration(this.media_, |
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this.media_.mediaSequence, |
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update.mediaSequence); |
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} |
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this.media_ = this.master.playlists[update.uri]; |
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}; |
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/** |
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* When switching variant playlists in a live stream, the player may |
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* discover that the new set of available segments is shifted in |
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* time relative to the old playlist. If that is the case, you can |
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* call this method to synchronize the playlist loader so that |
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* subsequent calls to getMediaIndexForTime_() return values |
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* appropriate for the new playlist. |
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* |
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* @param mediaIndex {integer} the index of the segment that will be |
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* the used to base timeline calculations on |
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* @param startTime {number} the media timeline position of the |
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* first moment of video data for the specified segment. That is, |
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* data from the specified segment will first be displayed when |
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* `currentTime` is equal to `startTime`. |
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*/ |
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PlaylistLoader.prototype.updateTimelineOffset = function(mediaIndex, startingTime) { |
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var segmentOffset = Playlist.duration(this.media_, |
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this.media_.mediaSequence, |
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this.media_.mediaSequence + mediaIndex); |
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this.expired_ = startingTime - segmentOffset; |
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}; |
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/** |
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* Determine the index of the segment that contains a specified |
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* playback position in the current media playlist. Early versions |
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@ -426,7 +419,7 @@ |
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// when the requested position is earlier than the current set of
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// segments, return the earliest segment index
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time -= this.expiredPreDiscontinuity_ + this.expiredPostDiscontinuity_; |
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time -= this.expired_; |
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if (time < 0) { |
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return 0; |
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} |
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David LaPalomento
10 years ago