/**
* @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.media.PresentationTimeline');
/**
* Creates a PresentationTimeline.
*
* @param {?number} presentationStartTime The wall-clock time, in seconds,
* when the presentation started or will start. Only required for live.
*
* @see {shakaExtern.Manifest}
*
* @constructor
* @struct
* @export
*/
shaka.media.PresentationTimeline = function(presentationStartTime) {
/** @private {?number} */
this.presentationStartTime_ = presentationStartTime;
/** @private {number} */
this.duration_ = Number.POSITIVE_INFINITY;
/** @private {number} */
this.segmentAvailabilityDuration_ = Number.POSITIVE_INFINITY;
/** @private {?number} */
this.maxSegmentDuration_ = 1;
/** @private {number} */
this.maxFirstSegmentStartTime_ = 0;
/** @private {number} */
this.clockOffset_ = 0;
};
/**
* @return {number} The presentation's duration in seconds.
* POSITIVE_INFINITY indicates that the presentation continues indefinitely.
*/
shaka.media.PresentationTimeline.prototype.getDuration = function() {
return this.duration_;
};
/**
* Sets the presentation's duration.
*
* @param {number} duration The presentation's duration in seconds.
* POSITIVE_INFINITY indicates that the presentation continues indefinitely.
*/
shaka.media.PresentationTimeline.prototype.setDuration = function(duration) {
goog.asserts.assert(duration > 0, 'duration must be > 0');
this.duration_ = duration;
};
/**
* Sets the clock offset, which is the the difference between the client's clock
* and the server's clock, in milliseconds (i.e., serverTime = Date.now() +
* clockOffset).
*
* @param {number} offset The clock offset, in ms.
*/
shaka.media.PresentationTimeline.prototype.setClockOffset = function(offset) {
this.clockOffset_ = offset;
};
/**
* Gets the presentation's segment availability duration, which is the amount
* of time, in seconds, that the start of a segment remains available after the
* live-edge moves past the end of that segment. POSITIVE_INFINITY indicates
* that segments remain available indefinitely. For example, if your live
* presentation has a 5 minute DVR window and your segments are 10 seconds long
* then the segment availability duration should be 4 minutes and 50 seconds.
*
* @return {number} The presentation's segment availability duration.
*/
shaka.media.PresentationTimeline.prototype.getSegmentAvailabilityDuration =
function() {
return this.segmentAvailabilityDuration_;
};
/**
* Sets the presentation's segment availability duration. The segment
* availability duration should only be set for live.
*
* @param {number} segmentAvailabilityDuration The presentation's new segment
* availability duration in seconds.
*/
shaka.media.PresentationTimeline.prototype.setSegmentAvailabilityDuration =
function(segmentAvailabilityDuration) {
goog.asserts.assert(segmentAvailabilityDuration >= 0,
'segmentAvailabilityDuration must be >= 0');
this.segmentAvailabilityDuration_ = segmentAvailabilityDuration;
};
/**
* Gives PresentationTimeline a Stream's segments so it can size and position
* the segment availability window, and account for missing segment
* information. This function should be called once for each Stream (no more,
* no less).
*
* @param {number} periodStartTime
* @param {!Array.<!shaka.media.SegmentReference>} references
*/
shaka.media.PresentationTimeline.prototype.notifySegments = function(
periodStartTime, references) {
if (references.length == 0)
return;
this.maxSegmentDuration_ = references.reduce(
function(max, r) { return Math.max(max, r.endTime - r.startTime); },
this.maxSegmentDuration_);
if (periodStartTime == 0) {
this.maxFirstSegmentStartTime_ =
Math.max(this.maxFirstSegmentStartTime_, references[0].startTime);
}
shaka.log.v1('notifySegments:',
'maxSegmentDuration=' + this.maxSegmentDuration_,
'maxFirstSegmentStartTime=' + this.maxFirstSegmentStartTime_);
};
/**
* Gives PresentationTimeline a Stream's maximum segment duration so it can
* size and position the segment availability window. This function should be
* called once for each Stream (no more, no less), but does not have to be
* called if notifySegments() is called instead for a particular stream.
*
* @param {number} maxSegmentDuration The maximum segment duration for a
* particular stream.
*/
shaka.media.PresentationTimeline.prototype.notifyMaxSegmentDuration = function(
maxSegmentDuration) {
this.maxSegmentDuration_ = Math.max(
this.maxSegmentDuration_, maxSegmentDuration);
shaka.log.v1('notifyNewSegmentDuration:',
'maxSegmentDuration=' + this.maxSegmentDuration_);
};
/**
* @return {boolean} True if the presentation is live; otherwise, return
* false.
*/
shaka.media.PresentationTimeline.prototype.isLive = function() {
return this.duration_ == Number.POSITIVE_INFINITY ||
this.segmentAvailabilityDuration_ < Number.POSITIVE_INFINITY;
};
/**
* Gets the presentation's current earliest, available timestamp. This value
* may be greater than the presentation's current segment availability start
* time if segment information is missing or does not exist at the beginning of
* the segment availability window.
*
* @return {number} The presentation's current earliest, available timestamp,
* in seconds, relative to the start of the presentation.
*/
shaka.media.PresentationTimeline.prototype.getEarliestStart = function() {
var maxFirstSegmentStartTime = Math.min(
this.maxFirstSegmentStartTime_, this.getSegmentAvailabilityEnd());
return Math.max(maxFirstSegmentStartTime,
this.getSegmentAvailabilityStart());
};
/**
* Gets the presentation's current segment availability start time. Segments
* ending at or before this time should be assumed to be unavailable.
*
* @return {number} The current segment availability start time, in seconds,
* relative to the start of the presentation.
*/
shaka.media.PresentationTimeline.prototype.getSegmentAvailabilityStart =
function() {
if (this.segmentAvailabilityDuration_ == Number.POSITIVE_INFINITY)
return 0;
return Math.max(
0, this.getSegmentAvailabilityEnd() - this.segmentAvailabilityDuration_);
};
/**
* Gets the presentation's current segment availability end time. Segments
* starting after this time should be assumed to be unavailable.
*
* @return {number} The current segment availability end time, in seconds,
* relative to the start of the presentation. Always returns the
* presentation's duration for video-on-demand.
*/
shaka.media.PresentationTimeline.prototype.getSegmentAvailabilityEnd =
function() {
if (this.presentationStartTime_ == null || !this.isLive())
return this.duration_;
return Math.min(this.getLiveEdge_(), this.duration_);
};
/**
* @return {number} The current presentation time in seconds.
* @private
*/
shaka.media.PresentationTimeline.prototype.getLiveEdge_ = function() {
goog.asserts.assert(this.presentationStartTime_ != null,
'Cannot compute timeline live edge without start time');
var now = (Date.now() + this.clockOffset_) / 1000.0;
return Math.max(
0, now - this.maxSegmentDuration_ - this.presentationStartTime_);
};