/**
* @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.text.Cue');
goog.require('shaka.util.Error');
goog.require('shaka.util.IDestroyable');
goog.require('shaka.util.MimeUtils');
/**
* Manages text parsers and cues.
*
* @param {shaka.extern.TextDisplayer} displayer
* @struct
* @constructor
* @implements {shaka.util.IDestroyable}
*/
shaka.text.TextEngine = function(displayer) {
/** @private {shaka.extern.TextParser} */
this.parser_ = null;
/** @private {shaka.extern.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 {string} */
this.selectedClosedCaptionId_ = '';
/**
* The closed captions map stores the CEA closed captions by closed captions
* id and start and end time.
* It's used as the buffer of closed caption text streams, to show captions
* when we start displaying captions or switch caption tracks, we need to be
* able to get the cues for the other language and display them without
* re-fetching the video segments they were embedded in.
* Structure of closed caption map:
* closed caption id -> {start and end time -> cues}
* @private {!Map.<string, !Map.<string, !Array.<shaka.text.Cue>>>} */
this.closedCaptionsMap_ = new Map();
};
/** @private {!Object.<string, !shaka.extern.TextParserPlugin>} */
shaka.text.TextEngine.parserMap_ = {};
/**
* @param {string} mimeType
* @param {!shaka.extern.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) {
if (shaka.text.TextEngine.parserMap_[mimeType]) {
// An actual parser is available.
return true;
}
if (window.muxjs &&
mimeType == shaka.util.MimeUtils.CLOSED_CAPTION_MIMETYPE) {
// Will be handled by mux.js.
return true;
}
return false;
};
/** @override */
shaka.text.TextEngine.prototype.destroy = function() {
this.parser_ = null;
this.displayer_ = null;
this.closedCaptionsMap_.clear();
return Promise.resolve();
};
/**
* @param {!shaka.extern.TextDisplayer} displayer
*/
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) {
// No parser for CEA, which is extracted from video and side-loaded
// into TextEngine and TextDisplayer.
if (mimeType == shaka.util.MimeUtils.CLOSED_CAPTION_MIMETYPE) {
return;
}
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 {shaka.extern.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 relative to the start of the presentation
* @param {?number} endTime relative to the start of the presentation
* @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 {shaka.extern.TextParser.TimeContext} **/
let time = {
periodStart: this.timestampOffset_,
segmentStart: startTime,
segmentEnd: 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(this.bufferEnd_ != null,
'There should already be a buffered range 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} startTime relative to the start of the presentation
* @param {number} endTime relative to the start of the presentation
* @return {!Promise}
*/
shaka.text.TextEngine.prototype.remove = function(startTime, endTime) {
// Start the operation asynchronously to avoid blocking the caller.
return Promise.resolve().then(function() {
if (this.displayer_ && this.displayer_.remove(startTime, endTime)) {
if (this.bufferStart_ == null) {
goog.asserts.assert(this.bufferEnd_ == null,
'end must be null if startTime is null');
} else {
goog.asserts.assert(this.bufferEnd_ != null,
'end must be non-null if startTime is non-null');
// Update buffered range.
if (endTime <= this.bufferStart_ || startTime >= this.bufferEnd_) {
// No intersection. Nothing was removed.
} else if (startTime <= this.bufferStart_ &&
endTime >= this.bufferEnd_) {
// We wiped out everything.
this.bufferStart_ = this.bufferEnd_ = null;
} else if (startTime <= this.bufferStart_ &&
endTime < this.bufferEnd_) {
// We removed from the beginning of the range.
this.bufferStart_ = endTime;
} else if (startTime > this.bufferStart_ &&
endTime >= this.bufferEnd_) {
// We removed from the end of the range.
this.bufferEnd_ = startTime;
} 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) {
if (this.bufferStart_ == null || this.bufferEnd_ == null) {
return false;
}
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_);
};
/**
* Set the selected closed captions id.
* Append the cues stored in the closed captions map until buffer end time.
* This is to fill the gap between buffered and unbuffered captions, and to
* avoid duplicates that would be caused by any future video segments parsed for
* captions.
*
* @param {string} id
* @param {number} bufferEndTime Load any stored cues up to this time.
*/
shaka.text.TextEngine.prototype.setSelectedClosedCaptionId =
function(id, bufferEndTime) {
this.selectedClosedCaptionId_ = id;
const captionsMap = this.closedCaptionsMap_.get(id);
if (captionsMap) {
for (const startAndEndTime of captionsMap.keys()) {
/** @type {Array.<!shaka.text.Cue>} */
const cues = captionsMap.get(startAndEndTime)
.filter((c) => c.endTime <= bufferEndTime);
if (cues) {
this.displayer_.append(cues);
}
}
}
};
/**
* Store the closed captions in the text engine, and append the cues to the text
* displayer. This is a side-channel used for embedded text only.
*
* @param {!Array.<muxjs.mp4.ClosedCaption>} closedCaptions
* @param {?number} startTime relative to the start of the presentation
* @param {?number} endTime relative to the start of the presentation
* @param {number} videoTimestampOffset the timestamp offset of the video
* stream in which these captions were embedded
*/
shaka.text.TextEngine.prototype.storeAndAppendClosedCaptions = function(
closedCaptions, startTime, endTime, videoTimestampOffset) {
const startAndEndTime = startTime + ' ' + endTime;
const captionsMap = new Map();
for (const caption of closedCaptions) {
const id = caption.stream;
if (!captionsMap.has(id)) {
captionsMap.set(id, new Map());
}
if (!captionsMap.get(id).has(startAndEndTime)) {
captionsMap.get(id).set(startAndEndTime, []);
}
// Adjust CEA captions with respect to the timestamp offset of the video
// stream in which they were embedded.
caption.startTime += videoTimestampOffset;
caption.endTime += videoTimestampOffset;
const keepThisCue =
caption.startTime >= this.appendWindowStart_ &&
caption.startTime < this.appendWindowEnd_;
if (!keepThisCue) {
continue;
}
/** @type {!shaka.text.Cue} */
const cue = new shaka.text.Cue(
caption.startTime, caption.endTime, caption.text);
captionsMap.get(id).get(startAndEndTime).push(cue);
if (id == this.selectedClosedCaptionId_) {
this.displayer_.append([cue]);
}
}
for (const id of captionsMap.keys()) {
if (!this.closedCaptionsMap_.has(id)) {
this.closedCaptionsMap_.set(id, new Map());
}
for (const startAndEndTime of captionsMap.get(id).keys()) {
const cues = captionsMap.get(id).get(startAndEndTime);
this.closedCaptionsMap_.get(id).set(startAndEndTime, cues);
}
}
if (this.bufferStart_ == null) {
this.bufferStart_ = Math.max(startTime, this.appendWindowStart_);
} else {
this.bufferStart_ = Math.min(
this.bufferStart_, Math.max(startTime, this.appendWindowStart_));
}
this.bufferEnd_ = Math.max(
this.bufferEnd_, Math.min(endTime, this.appendWindowEnd_));
};
/**
* Get the number of closed caption channels.
*
* This function is for TESTING ONLY. DO NOT USE in the library.
*
* @return {number}
*/
shaka.text.TextEngine.prototype.getNumberOfClosedCaptionChannels = function() {
return this.closedCaptionsMap_.size;
};
/**
* Get the number of closed caption cues for a given channel. If there is
* no channel for the given channel id, this will return 0.
*
* This function is for TESTING ONLY. DO NOT USE in the library.
*
* @param {string} channelId
* @return {number}
*/
shaka.text.TextEngine.prototype.getNumberOfClosedCaptionsInChannel =
function(channelId) {
const channel = this.closedCaptionsMap_.get(channelId);
return channel ? channel.size : 0;
};