/**
* @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.TextEngine');
goog.require('goog.asserts');
goog.require('shaka.log');
goog.require('shaka.util.IDestroyable');
/**
* Manages text parsers and cues.
*
* @struct
* @constructor
* @param {TextTrack} track
* @implements {shaka.util.IDestroyable}
*/
shaka.media.TextEngine = function(track) {
/** @private {shakaExtern.TextParser} */
this.parser_ = null;
/** @private {TextTrack} */
this.track_ = track;
/** @private {number} */
this.timestampOffset_ = 0;
/** @private {number} */
this.appendWindowEnd_ = Infinity;
/** @private {?number} */
this.bufferStart_ = null;
/** @private {?number} */
this.bufferEnd_ = null;
};
/** @private {!Object.<string, !shakaExtern.TextParserPlugin>} */
shaka.media.TextEngine.parserMap_ = {};
/**
* @param {string} mimeType
* @param {!shakaExtern.TextParserPlugin} plugin
* @export
*/
shaka.media.TextEngine.registerParser = function(mimeType, plugin) {
// Assume that if the function is expecting no parameters, it must be
// a stateful text parser factory. Otherwise, assume that it is a
// stateless text parser.
if (plugin.length == 0) {
shaka.media.TextEngine.parserMap_[mimeType] = plugin;
} else {
shaka.log.warning('The use of stateless text parsers is deprecated.');
shaka.media.TextEngine.parserMap_[mimeType] =
shaka.media.TextEngine.TextParserWrapper_.bind(null, plugin);
}
};
/**
* @param {string} mimeType
* @export
*/
shaka.media.TextEngine.unregisterParser = function(mimeType) {
delete shaka.media.TextEngine.parserMap_[mimeType];
};
/**
* @param {string} mimeType
* @return {boolean}
*/
shaka.media.TextEngine.isTypeSupported = function(mimeType) {
return !!shaka.media.TextEngine.parserMap_[mimeType];
};
/**
* Creates a cue using the best platform-specific interface available.
*
* @param {number} startTime
* @param {number} endTime
* @param {string} payload
* @return {TextTrackCue} or null if the parameters were invalid.
* @export
*/
shaka.media.TextEngine.makeCue = function(startTime, endTime, payload) {
if (startTime >= endTime) {
// IE/Edge will throw in this case.
// See issue #501
shaka.log.warning('Invalid cue times: ' + startTime + ' - ' + endTime);
return null;
}
return new VTTCue(startTime, endTime, payload);
};
/** @override */
shaka.media.TextEngine.prototype.destroy = function() {
if (this.track_) {
this.removeWhere_(function(cue) { return true; });
}
this.parser_ = null;
this.track_ = null;
return Promise.resolve();
};
/**
* Initialize the parser. This can be called multiple times, but must be called
* at least once before appendBuffer.
*
* @param {string} mimeType
*/
shaka.media.TextEngine.prototype.initParser = function(mimeType) {
var factory = shaka.media.TextEngine.parserMap_[mimeType];
goog.asserts.assert(
factory,
'Text type negotiation should have happened already');
this.parser_ = new factory();
};
/**
* @param {!ArrayBuffer} buffer
* @param {?number} startTime
* @param {?number} endTime
* @return {!Promise}
*/
shaka.media.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.track_) return;
if (startTime == null || endTime == null) {
this.parser_.parseInit(buffer);
return;
}
/** @type {shakaExtern.TextParser.TimeContext} **/
var time = {
periodStart: this.timestampOffset_,
segmentStart: startTime,
segmentEnd: endTime
};
// Parse the buffer and add the new cues.
var cues = this.parser_.parseMedia(buffer, time);
for (var i = 0; i < cues.length; ++i) {
if (cues[i].startTime >= this.appendWindowEnd_) break;
this.track_.addCue(cues[i]);
}
// 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_ = startTime;
} 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.media.TextEngine.prototype.remove = function(start, end) {
// Start the operation asynchronously to avoid blocking the caller.
return Promise.resolve().then(function() {
// Check that TextEngine hasn't been destroyed.
if (!this.track_) return;
this.removeWhere_(function(cue) {
if (cue.startTime >= end || cue.endTime <= start) {
// Outside the remove range. Hang on to it.
return false;
}
return true;
});
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.
goog.asserts.assert(
this.track_.cues.length == 0, 'should be no cues left');
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.media.TextEngine.prototype.setTimestampOffset =
function(timestampOffset) {
this.timestampOffset_ = timestampOffset;
};
/** @param {number} windowEnd */
shaka.media.TextEngine.prototype.setAppendWindowEnd =
function(windowEnd) {
this.appendWindowEnd_ = windowEnd;
};
/**
* @return {?number} Time in seconds of the beginning of the buffered range,
* or null if nothing is buffered.
*/
shaka.media.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.media.TextEngine.prototype.bufferEnd = function() {
return this.bufferEnd_;
};
/**
* @param {number} t A timestamp
* @return {boolean}
*/
shaka.media.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.media.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_);
};
/**
* Remove all cues for which the matching function returns true.
*
* @param {function(!TextTrackCue):boolean} predicate
* @private
*/
shaka.media.TextEngine.prototype.removeWhere_ = function(predicate) {
var cues = this.track_.cues;
var removeMe = [];
// Remove these in another loop to avoid mutating the TextTrackCueList
// while iterating over it. This allows us to avoid making assumptions
// about whether or not this.track_.remove() will alter that list.
for (var i = 0; i < cues.length; ++i) {
if (predicate(cues[i])) {
removeMe.push(cues[i]);
}
}
for (var i = 0; i < removeMe.length; ++i) {
this.track_.removeCue(removeMe[i]);
}
};
/**
* @param {Function} parser
* @constructor
* @implements {shakaExtern.TextParser}
* @private
*/
shaka.media.TextEngine.TextParserWrapper_ = function(parser) {
this.parser = parser;
};
/** @override **/
shaka.media.TextEngine.TextParserWrapper_.prototype.parseInit = function(data) {
this.parser(data, 0, null, null);
};
/** @override **/
shaka.media.TextEngine.TextParserWrapper_.prototype.parseMedia = function(
data, time) {
return this.parser(data,
time.periodStart,
time.segmentStart,
time.segmentEnd);
};