/** * @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.} */ 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) { var 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} **/ var time = { periodStart: 0, segmentStart: 0, segmentEnd: 0 }; // Parse the buffer and extract the first cue start time. try { var 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} **/ var time = { periodStart: this.timestampOffset_, segmentStart: startTime, segmentEnd: endTime }; // Parse the buffer and add the new cues. var allCues = this.parser_.parseMedia(new Uint8Array(buffer), time); var 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_); };