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Move Trick Play Out of Video Wrapper
This change moves the trick play logic out of the video wrapper so that it will be more available to the src= code. By doing this, I hope that we can make it clearer how we are working with the playback rate and ensure a tighter integration with it. Issue #816 Issue #997 Change-Id: Id462cda2c5eb82c3713237341424b91891bd38ea
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| /** | ||
| * @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. | ||
| */ | ||
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| goog.provide('shaka.media.PlayRateController'); | ||
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| goog.require('shaka.util.IReleasable'); | ||
| goog.require('shaka.util.Timer'); | ||
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| /** | ||
| * The play rate controller controls the playback rate on the media element. | ||
| * This provides some missing functionality (e.g. negative playback rate). If | ||
| * the playback rate on the media element can change outside of the controller, | ||
| * the playback controller will need to be updated to stay in-sync. | ||
| * | ||
| * @implements {shaka.util.IReleasable} | ||
| * @final | ||
| */ | ||
| shaka.media.PlayRateController = class { | ||
| /** | ||
| * @param {shaka.media.PlayRateController.Harness} harness | ||
| */ | ||
| constructor(harness) { | ||
| /** @private {?shaka.media.PlayRateController.Harness} */ | ||
| this.harness_ = harness; | ||
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| /** @private {!Set.<shaka.media.PlayRateController.Modifier>} */ | ||
| this.modifiers_ = new Set(); | ||
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| /** @private {number} */ | ||
| this.rate_ = this.harness_.getRate(); | ||
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| /** @private {number} */ | ||
| this.pollRate_ = 0.25; | ||
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| /** @private {shaka.util.Timer} */ | ||
| this.timer_ = new shaka.util.Timer(() => { | ||
| this.harness_.movePlayhead(this.rate_ * this.pollRate_); | ||
| }); | ||
| } | ||
|
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| /** @override */ | ||
| release() { | ||
| if (this.timer_) { | ||
| this.timer_.stop(); | ||
| this.timer_ = null; | ||
| } | ||
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| this.harness_ = null; | ||
| } | ||
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| /** | ||
| * Add a modifier to the controller. If the modifier has already been applied, | ||
| * this will be a no-op. Calling |removeModifier| will remove all instances of | ||
| * this modifier from the controller. | ||
| * | ||
| * @param {shaka.media.PlayRateController.Modifier} modifier | ||
| */ | ||
| addModifier(modifier) { | ||
| this.modifiers_.add(modifier); | ||
| this.apply_(); | ||
| } | ||
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| /** | ||
| * Remove |modifier| from the controller. If the modifier was never applied, | ||
| * this will be a no-op. If the modifier was applied multiple times, this will | ||
| * remove all instances of it. | ||
| * | ||
| * @param {shaka.media.PlayRateController.Modifier} modifier | ||
| */ | ||
| removeModifier(modifier) { | ||
| this.modifiers_.delete(modifier); | ||
| this.apply_(); | ||
| } | ||
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| /** | ||
| * Set the playback rate. This rate will only be used as provided when there | ||
| * are not modifiers. If the rate needs to be set to zero, it is suggested | ||
| * that you use the ZERO_RATE modifier instead. | ||
| * | ||
| * @param {number} rate | ||
| */ | ||
| set(rate) { | ||
| this.rate_ = rate; | ||
| this.apply_(); | ||
| } | ||
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| /** | ||
| * Get the rate that the user will experience. This means that if we are using | ||
| * trick play, this will report the trick play rate. If we are buffering, this | ||
| * will report zero. If playback is occurring as normal, this will report 1. | ||
| * | ||
| * @return {number} | ||
| */ | ||
| getActiveRate() { | ||
| return this.calculateCurrentRate_(); | ||
| } | ||
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| /** | ||
| * Reapply the effects of |this.rate_| and |this.active_| to the media | ||
| * element. This will only update the rate via the harness if the desired rate | ||
| * has changed. | ||
| * | ||
| * @private | ||
| */ | ||
| apply_() { | ||
| // Always stop the timer. We may not start it again. | ||
| this.timer_.stop(); | ||
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| /** @type {number} */ | ||
| const rate = this.calculateCurrentRate_(); | ||
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| if (rate >= 0) { | ||
| this.applyRate_(rate); | ||
| return; | ||
| } | ||
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| // When moving backwards, set the playback rate to 0 so that we can manually | ||
| // seek backwards with out fighting the playhead. | ||
| this.timer_.tickEvery(this.pollRate_); | ||
| this.applyRate_(0); | ||
| } | ||
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| /** | ||
| * Calculate the rate that the controller wants the media element to have | ||
| * based on the current state of the controller. | ||
| * | ||
| * @return {number} | ||
| * @private | ||
| */ | ||
| calculateCurrentRate_() { | ||
| // We assume that all modifiers affect the play rate in the same way, | ||
| // setting it to zero. So if there are any modifiers, we should use a rate | ||
| // equal to zero. | ||
| return this.modifiers_.size ? 0 : this.rate_; | ||
| } | ||
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| /** | ||
| * If the new rate is different than the media element's playback rate, this | ||
| * will change the playback rate. If the rate does not need to change, it will | ||
| * not be set. This will avoid unnecessary ratechange events. | ||
| * | ||
| * @param {number} newRate | ||
| * @return {boolean} | ||
| * @private | ||
| */ | ||
| applyRate_(newRate) { | ||
| const oldRate = this.harness_.getRate(); | ||
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| if (oldRate != newRate) { | ||
| this.harness_.setRate(newRate); | ||
| } | ||
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| return oldRate != newRate; | ||
| } | ||
| }; | ||
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| /** | ||
| * Modifiers are differ types of modifications that can be applied to the play | ||
| * rate controller than will affect what playback rate is used. Right now all | ||
| * modifiers will override the playback rate to 0. | ||
| * | ||
| * @enum {number} | ||
| */ | ||
| shaka.media.PlayRateController.Modifier = { | ||
| ZERO_RATE: 0, | ||
| BUFFERING: 1, | ||
| }; | ||
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| /** | ||
| * @typedef {{ | ||
| * getRate: function():number, | ||
| * setRate: function(number), | ||
| * movePlayhead: function(number) | ||
| * }} | ||
| * | ||
| * @description | ||
| * A layer of abstraction between the controller and what it is controlling. | ||
| * In tests this will be implemented with spies. In production this will be | ||
| * implemented using a media element. | ||
| * | ||
| * @property {function():number} getRate | ||
| * Get the current playback rate being seen by the user. | ||
| * | ||
| * @property {function(number)} setRate | ||
| * Set the playback rate that the user should see. | ||
| * | ||
| * @property {function(number)} movePlayhead | ||
| * Move the playhead N seconds. If N is positive, the playhead will move | ||
| * forward abs(N) seconds. If N is negative, the playhead will move backwards | ||
| * abs(N) seconds. | ||
| */ | ||
| shaka.media.PlayRateController.Harness; |
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