/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.media.GapJumpingController');
goog.require('shaka.log');
goog.require('shaka.media.PresentationTimeline');
goog.require('shaka.media.StallDetector');
goog.require('shaka.media.TimeRangesUtils');
goog.require('shaka.util.EventManager');
goog.require('shaka.util.FakeEvent');
goog.require('shaka.util.IReleasable');
goog.require('shaka.util.Timer');
/**
* GapJumpingController handles jumping gaps that appear within the content.
* This will only jump gaps between two buffered ranges, so we should not have
* to worry about the availability window.
*
* @implements {shaka.util.IReleasable}
*/
shaka.media.GapJumpingController = class {
/**
* @param {!HTMLMediaElement} video
* @param {!shaka.media.PresentationTimeline} timeline
* @param {shaka.extern.StreamingConfiguration} config
* @param {shaka.media.StallDetector} stallDetector
* The stall detector is used to keep the playhead moving while in a
* playable region. The gap jumping controller takes ownership over the
* stall detector.
* If no stall detection logic is desired, |null| may be provided.
* @param {function(!Event)} onEvent
* Called when an event is raised to be sent to the application.
*/
constructor(video, timeline, config, stallDetector, onEvent) {
/** @private {?function(!Event)} */
this.onEvent_ = onEvent;
/** @private {HTMLMediaElement} */
this.video_ = video;
/** @private {?shaka.media.PresentationTimeline} */
this.timeline_ = timeline;
/** @private {?shaka.extern.StreamingConfiguration} */
this.config_ = config;
/** @private {shaka.util.EventManager} */
this.eventManager_ = new shaka.util.EventManager();
/** @private {boolean} */
this.seekingEventReceived_ = false;
/** @private {number} */
this.prevReadyState_ = video.readyState;
/** @private {number} */
this.startTime_ = 0;
/** @private {number} */
this.gapsJumped_ = 0;
/**
* The stall detector tries to keep the playhead moving forward. It is
* managed by the gap-jumping controller to avoid conflicts. On some
* platforms, the stall detector is not wanted, so it may be null.
*
* @private {shaka.media.StallDetector}
*/
this.stallDetector_ = stallDetector;
/** @private {boolean} */
this.hadSegmentAppended_ = false;
this.eventManager_.listen(video, 'waiting', () => this.onPollGapJump_());
/**
* We can't trust |readyState| or 'waiting' events on all platforms. To make
* up for this, we poll the current time. If we think we are in a gap, jump
* out of it.
*
* See: https://bit.ly/2McuXxm and https://bit.ly/2K5xmJO
*
* @private {?shaka.util.Timer}
*/
this.gapJumpTimer_ = new shaka.util.Timer(() => {
this.onPollGapJump_();
}).tickEvery(this.config_.gapJumpTimerTime);
}
/** @override */
release() {
if (this.eventManager_) {
this.eventManager_.release();
this.eventManager_ = null;
}
if (this.gapJumpTimer_ != null) {
this.gapJumpTimer_.stop();
this.gapJumpTimer_ = null;
}
if (this.stallDetector_) {
this.stallDetector_.release();
this.stallDetector_ = null;
}
this.onEvent_ = null;
this.timeline_ = null;
this.video_ = null;
}
/**
* Called when a segment is appended by StreamingEngine, but not when a clear
* is pending. This means StreamingEngine will continue buffering forward from
* what is buffered. So we know about any gaps before the start.
*/
onSegmentAppended() {
this.hadSegmentAppended_ = true;
this.onPollGapJump_();
}
/**
* Called when playback has started and the video element is
* listening for seeks.
*
* @param {number} startTime
*/
onStarted(startTime) {
if (this.video_.seeking && !this.seekingEventReceived_) {
this.seekingEventReceived_ = true;
this.startTime_ = startTime;
}
}
/** Called when a seek has started. */
onSeeking() {
this.seekingEventReceived_ = true;
this.hadSegmentAppended_ = false;
}
/**
* Returns the total number of playback gaps jumped.
* @return {number}
*/
getGapsJumped() {
return this.gapsJumped_;
}
/**
* Called on a recurring timer to check for gaps in the media. This is also
* called in a 'waiting' event.
*
* @private
*/
onPollGapJump_() {
// Don't gap jump before the video is ready to play.
if (this.video_.readyState == 0) {
return;
}
// Do not gap jump if seeking has begun, but the seeking event has not
// yet fired for this particular seek.
if (this.video_.seeking) {
if (!this.seekingEventReceived_) {
return;
}
} else {
this.seekingEventReceived_ = false;
}
// Don't gap jump while paused, so that you don't constantly jump ahead
// while paused on a livestream. We make an exception for time 0, since we
// may be _required_ to seek on startup before play can begin, but only if
// autoplay is enabled.
if (this.video_.paused && (this.video_.currentTime != this.startTime_ ||
(!this.video_.autoplay && this.video_.currentTime == this.startTime_))) {
return;
}
// When the ready state changes, we have moved on, so we should fire the
// large gap event if we see one.
if (this.video_.readyState != this.prevReadyState_) {
this.prevReadyState_ = this.video_.readyState;
}
if (this.stallDetector_ && this.stallDetector_.poll()) {
// Some action was taken by StallDetector, so don't do anything yet.
return;
}
const currentTime = this.video_.currentTime;
const buffered = this.video_.buffered;
const gapDetectionThreshold = this.config_.gapDetectionThreshold;
const gapIndex = shaka.media.TimeRangesUtils.getGapIndex(
buffered, currentTime, gapDetectionThreshold);
// The current time is unbuffered or is too far from a gap.
if (gapIndex == null) {
return;
}
// If we are before the first buffered range, this could be an unbuffered
// seek. So wait until a segment is appended so we are sure it is a gap.
if (gapIndex == 0 && !this.hadSegmentAppended_) {
return;
}
// StreamingEngine can buffer past the seek end, but still don't allow
// seeking past it.
const jumpTo = buffered.start(gapIndex);
const seekEnd = this.timeline_.getSeekRangeEnd();
if (jumpTo >= seekEnd) {
return;
}
const jumpSize = jumpTo - currentTime;
// If we jump to exactly the gap start, we may detect a small gap due to
// rounding errors or browser bugs. We can ignore these extremely small
// gaps since the browser should play through them for us.
if (jumpSize < shaka.media.GapJumpingController.BROWSER_GAP_TOLERANCE) {
return;
}
if (gapIndex == 0) {
shaka.log.info(
'Jumping forward', jumpSize,
'seconds because of gap before start time of', jumpTo);
} else {
shaka.log.info(
'Jumping forward', jumpSize, 'seconds because of gap starting at',
buffered.end(gapIndex - 1), 'and ending at', jumpTo);
}
this.video_.currentTime = jumpTo;
// This accounts for the possibility that we jump a gap at the start
// position but we jump _into_ another gap. By setting the start
// position to the new jumpTo we ensure that the check above will
// pass even though the video is still paused.
if (currentTime == this.startTime_) {
this.startTime_ = jumpTo;
}
this.gapsJumped_++;
this.onEvent_(
new shaka.util.FakeEvent(shaka.util.FakeEvent.EventName.GapJumped));
}
};
/**
* The limit, in seconds, for the gap size that we will assume the browser will
* handle for us.
* @const
*/
shaka.media.GapJumpingController.BROWSER_GAP_TOLERANCE = 0.001;