/**
* @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.text.TextEngine');
goog.require('goog.asserts');
goog.require('shaka.util.Error');
goog.require('shaka.util.IDestroyable');
/**
* Manages text parsers and cues.
*
* @param {shakaExtern.TextDisplayer} displayer
* @struct
* @constructor
* @implements {shaka.util.IDestroyable}
*/
shaka.text.TextEngine = function(displayer) {
/** @private {shakaExtern.TextParser} */
this.parser_ = null;
/** @private {shakaExtern.TextDisplayer} */
this.displayer_ = displayer;
/** @private {number} */
this.timestampOffset_ = 0;
/** @private {number} */
this.appendWindowStart_ = 0;
/** @private {number} */
this.appendWindowEnd_ = Infinity;
/** @private {?number} */
this.bufferStart_ = null;
/** @private {?number} */
this.bufferEnd_ = null;
};
/** @private {!Object.<string, !shakaExtern.TextParserPlugin>} */
shaka.text.TextEngine.parserMap_ = {};
/**
* @param {string} mimeType
* @param {!shakaExtern.TextParserPlugin} plugin
* @export
*/
shaka.text.TextEngine.registerParser = function(mimeType, plugin) {
shaka.text.TextEngine.parserMap_[mimeType] = plugin;
};
/**
* @param {string} mimeType
* @export
*/
shaka.text.TextEngine.unregisterParser = function(mimeType) {
delete shaka.text.TextEngine.parserMap_[mimeType];
};
/**
* @param {string} mimeType
* @return {boolean}
*/
shaka.text.TextEngine.isTypeSupported = function(mimeType) {
return !!shaka.text.TextEngine.parserMap_[mimeType];
};
/** @override */
shaka.text.TextEngine.prototype.destroy = function() {
this.parser_ = null;
this.displayer_ = null;
return Promise.resolve();
};
/**
* @param {shakaExtern.TextDisplayer} displayer
* @export
*/
shaka.text.TextEngine.prototype.setDisplayer = function(displayer) {
this.displayer_ = displayer;
};
/**
* Initialize the parser. This can be called multiple times, but must be called
* at least once before appendBuffer.
*
* @param {string} mimeType
*/
shaka.text.TextEngine.prototype.initParser = function(mimeType) {
let factory = shaka.text.TextEngine.parserMap_[mimeType];
goog.asserts.assert(
factory,
'Text type negotiation should have happened already');
this.parser_ = new factory();
};
/**
* Parse the start time from the text media segment, if possible.
*
* @param {!ArrayBuffer} buffer
* @return {number}
* @throws {shaka.util.Error} on failure
*/
shaka.text.TextEngine.prototype.getStartTime = function(buffer) {
goog.asserts.assert(this.parser_, 'The parser should already be initialized');
/** @type {shakaExtern.TextParser.TimeContext} **/
let time = {
periodStart: 0,
segmentStart: null,
segmentEnd: 0
};
// Parse the buffer and extract the first cue start time.
try {
let allCues = this.parser_.parseMedia(new Uint8Array(buffer), time);
return allCues[0].startTime;
} catch (exception) {
// This could be a failure from the parser itself (init segment required)
// or an exception from allCues.length being zero.
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.TEXT,
shaka.util.Error.Code.UNABLE_TO_EXTRACT_CUE_START_TIME,
exception);
}
};
/**
* @param {!ArrayBuffer} buffer
* @param {?number} startTime
* @param {?number} endTime
* @return {!Promise}
*/
shaka.text.TextEngine.prototype.appendBuffer =
function(buffer, startTime, endTime) {
goog.asserts.assert(this.parser_, 'The parser should already be initialized');
// Start the operation asynchronously to avoid blocking the caller.
return Promise.resolve().then(function() {
// Check that TextEngine hasn't been destroyed.
if (!this.parser_ || !this.displayer_) return;
if (startTime == null || endTime == null) {
this.parser_.parseInit(new Uint8Array(buffer));
return;
}
/** @type {shakaExtern.TextParser.TimeContext} **/
let time = {
periodStart: this.timestampOffset_,
segmentStart: this.timestampOffset_ + startTime,
segmentEnd: this.timestampOffset_ + endTime
};
// Parse the buffer and add the new cues.
let allCues = this.parser_.parseMedia(new Uint8Array(buffer), time);
let cuesToAppend = allCues.filter(function(cue) {
return cue.startTime >= this.appendWindowStart_ &&
cue.startTime < this.appendWindowEnd_;
}.bind(this));
this.displayer_.append(cuesToAppend);
// NOTE: We update the buffered range from the start and end times passed
// down from the segment reference, not with the start and end times of the
// parsed cues. This is important because some segments may contain no
// cues, but we must still consider those ranges buffered.
if (this.bufferStart_ == null) {
this.bufferStart_ = Math.max(startTime, this.appendWindowStart_);
} else {
// We already had something in buffer, and we assume we are extending the
// range from the end.
goog.asserts.assert((startTime - this.bufferEnd_) <= 1,
'There should not be a gap in text references >1s');
}
this.bufferEnd_ = Math.min(endTime, this.appendWindowEnd_);
}.bind(this));
};
/**
* @param {number} start
* @param {number} end
* @return {!Promise}
*/
shaka.text.TextEngine.prototype.remove = function(start, end) {
// Start the operation asynchronously to avoid blocking the caller.
return Promise.resolve().then(function() {
if (this.displayer_ && this.displayer_.remove(start, end)) {
if (this.bufferStart_ == null) {
goog.asserts.assert(this.bufferEnd_ == null,
'end must be null if start is null');
} else {
goog.asserts.assert(this.bufferEnd_ != null,
'end must be non-null if start is non-null');
// Update buffered range.
if (end <= this.bufferStart_ || start >= this.bufferEnd_) {
// No intersection. Nothing was removed.
} else if (start <= this.bufferStart_ && end >= this.bufferEnd_) {
// We wiped out everything.
this.bufferStart_ = this.bufferEnd_ = null;
} else if (start <= this.bufferStart_ && end < this.bufferEnd_) {
// We removed from the beginning of the range.
this.bufferStart_ = end;
} else if (start > this.bufferStart_ && end >= this.bufferEnd_) {
// We removed from the end of the range.
this.bufferEnd_ = start;
} else {
// We removed from the middle? StreamingEngine isn't supposed to.
goog.asserts.assert(
false, 'removal from the middle is not supported by TextEngine');
}
}
}
}.bind(this));
};
/** @param {number} timestampOffset */
shaka.text.TextEngine.prototype.setTimestampOffset =
function(timestampOffset) {
this.timestampOffset_ = timestampOffset;
};
/**
* @param {number} appendWindowStart
* @param {number} appendWindowEnd
*/
shaka.text.TextEngine.prototype.setAppendWindow =
function(appendWindowStart, appendWindowEnd) {
this.appendWindowStart_ = appendWindowStart;
this.appendWindowEnd_ = appendWindowEnd;
};
/**
* @return {?number} Time in seconds of the beginning of the buffered range,
* or null if nothing is buffered.
*/
shaka.text.TextEngine.prototype.bufferStart = function() {
return this.bufferStart_;
};
/**
* @return {?number} Time in seconds of the end of the buffered range,
* or null if nothing is buffered.
*/
shaka.text.TextEngine.prototype.bufferEnd = function() {
return this.bufferEnd_;
};
/**
* @param {number} t A timestamp
* @return {boolean}
*/
shaka.text.TextEngine.prototype.isBuffered = function(t) {
return t >= this.bufferStart_ && t < this.bufferEnd_;
};
/**
* @param {number} t A timestamp
* @return {number} Number of seconds ahead of 't' we have buffered
*/
shaka.text.TextEngine.prototype.bufferedAheadOf = function(t) {
if (this.bufferEnd_ == null || this.bufferEnd_ < t) return 0;
goog.asserts.assert(
this.bufferStart_ != null, 'start should not be null if end is not null');
return this.bufferEnd_ - Math.max(t, this.bufferStart_);
};
/**
* Append cues to text displayer.
*
* @param {!Array.<!shaka.text.Cue>} cues
* @export
*/
shaka.text.TextEngine.prototype.appendCues = function(cues) {
this.displayer_.append(cues);
};