mirror of
https://github.com/shaka-project/shaka-player.git
synced 2026-06-14 15:56:38 +03:00
Sandra Lokshina
c70367dc97
Closes #796. Closes #923. Change-Id: Ifc2017b40a0fb570103f0fed7bc130aa24819e9f
353 lines
10 KiB
JavaScript
353 lines
10 KiB
JavaScript
/**
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* @license
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* Copyright 2016 Google Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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goog.provide('shaka.text.Mp4VttParser');
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goog.require('goog.asserts');
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goog.require('shaka.log');
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goog.require('shaka.text.Cue');
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goog.require('shaka.text.TextEngine');
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goog.require('shaka.text.VttTextParser');
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goog.require('shaka.util.DataViewReader');
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goog.require('shaka.util.Error');
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goog.require('shaka.util.Functional');
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goog.require('shaka.util.Mp4Parser');
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goog.require('shaka.util.StringUtils');
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goog.require('shaka.util.TextParser');
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/**
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* @struct
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* @constructor
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* @implements {shakaExtern.TextParser}
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*/
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shaka.text.Mp4VttParser = function() {
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/**
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* The current time scale used by the VTT parser.
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*
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* @type {?number}
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* @private
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*/
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this.timescale_ = null;
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};
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/** @override */
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shaka.text.Mp4VttParser.prototype.parseInit = function(data) {
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var Mp4Parser = shaka.util.Mp4Parser;
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var sawWVTT = false;
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new Mp4Parser()
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.box('moov', Mp4Parser.children)
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.box('trak', Mp4Parser.children)
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.box('mdia', Mp4Parser.children)
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.fullBox('mdhd', function(box) {
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goog.asserts.assert(
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box.version == 0 || box.version == 1,
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'MDHD version can only be 0 or 1');
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if (box.version == 0) {
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box.reader.skip(4); // skip "creation_time"
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box.reader.skip(4); // skip "modification_time"
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this.timescale_ = box.reader.readUint32();
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box.reader.skip(4); // skip "duration"
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} else {
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box.reader.skip(8); // skip "creation_time"
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box.reader.skip(8); // skip "modification_time"
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this.timescale_ = box.reader.readUint32();
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box.reader.skip(8); // skip "duration"
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}
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box.reader.skip(4); // skip "pad", "language", and "pre-defined"
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}.bind(this))
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.box('minf', Mp4Parser.children)
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.box('stbl', Mp4Parser.children)
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.fullBox('stsd', Mp4Parser.sampleDescription)
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.box('wvtt', function(box) {
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// A valid vtt init segment, no actual subtitles yet
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sawWVTT = true;
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}).parse(data);
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if (!this.timescale_) {
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// Missing timescale for VTT content. Should be located in the MDHD
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throw new shaka.util.Error(
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shaka.util.Error.Severity.CRITICAL,
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shaka.util.Error.Category.TEXT,
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shaka.util.Error.Code.INVALID_MP4_VTT);
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}
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if (!sawWVTT) {
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// A WVTT box should have been seen (a valid vtt init segment with no
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// actual subtitles).
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throw new shaka.util.Error(
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shaka.util.Error.Severity.CRITICAL,
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shaka.util.Error.Category.TEXT,
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shaka.util.Error.Code.INVALID_MP4_VTT);
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}
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};
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/** @override */
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shaka.text.Mp4VttParser.prototype.parseMedia = function(data, time) {
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var Mp4VttParser = shaka.text.Mp4VttParser;
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var Mp4Parser = shaka.util.Mp4Parser;
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var baseTime = 0;
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/** @type {!Array.<shaka.text.Mp4VttParser.TimeSegment>} */
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var presentations = [];
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/** @type {!Array.<ArrayBuffer>} */
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var payloads = [];
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/** @type {!Array.<shaka.text.Cue>} */
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var cues = [];
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var sawTFDT = false;
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var sawTRUN = false;
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var sawMDAT = false;
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new Mp4Parser()
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.box('moof', Mp4Parser.children)
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.box('traf', Mp4Parser.children)
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.fullBox('tfdt', function(box) {
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sawTFDT = true;
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goog.asserts.assert(
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box.version == 0 || box.version == 1,
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'TFDT version can only be 0 or 1');
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baseTime = (box.version == 0) ?
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box.reader.readUint32() :
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box.reader.readUint64();
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})
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.fullBox('trun', function(box) {
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sawTRUN = true;
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goog.asserts.assert(
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box.version != null,
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'A TRUN box should have a valid version value');
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goog.asserts.assert(
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box.flags != null,
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'A TRUN box should have a valid flags value');
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presentations = Mp4VttParser.parseTRUN_(
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box.version, box.flags, box.reader);
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})
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.box('vtte', function(box) {
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// VTTE are empty cues, so there is no need to do any more than insert
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// a place-holder. We must add something or else the ordering between
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// the payloads and presentation times would fall out of order.
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payloads.push(null);
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})
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.box('vttc', Mp4Parser.allData(function(data) {
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payloads.push(data.buffer);
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}))
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.box('mdat', function(box) {
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sawMDAT = true;
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Mp4Parser.children(box);
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}).parse(data);
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if (!sawMDAT && !sawTFDT && !sawTRUN) {
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// A required box is missing
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throw new shaka.util.Error(
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shaka.util.Error.Severity.CRITICAL,
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shaka.util.Error.Category.TEXT,
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shaka.util.Error.Code.INVALID_MP4_VTT);
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}
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goog.asserts.assert(
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presentations.length == payloads.length,
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'The number of presentations should equal the number of payloads');
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var currentTime = baseTime;
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for (var i = 0; i < presentations.length; i++) {
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var presentation = presentations[i];
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var payload = payloads[i];
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if (presentation.duration) {
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var startTime = presentation.timeOffset ?
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baseTime + presentation.timeOffset :
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currentTime;
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currentTime = startTime + presentation.duration;
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// The payload can be null as that would mean that it was a VTTE and
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// was only inserted to keep the presentation times in sync with the
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// payloads.
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if (payload) {
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cues.push(shaka.text.Mp4VttParser.parseVTTC_(
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payload,
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time.periodStart + startTime / this.timescale_,
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time.periodStart + currentTime / this.timescale_));
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}
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}
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}
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return cues.filter(shaka.util.Functional.isNotNull);
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};
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/**
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* @typedef {{
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* duration: ?number,
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* timeOffset: ?number
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* }}
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*
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* @property {?number} duration
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* The length of the segment in timescale units.
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* @property {?number} timeOffset
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* The time since the start of the segment in timescale units. Time
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* offset is based of the start of the segment. If this value is
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* missing, the accumated durations preceeding this time segment will
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* be used to create the start time.
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*/
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shaka.text.Mp4VttParser.TimeSegment;
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/**
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* @param {number} version
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* @param {number} flags
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* @param {!shaka.util.DataViewReader} reader
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* @return {!Array.<shaka.text.Mp4VttParser.TimeSegment>}
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* @private
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*/
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shaka.text.Mp4VttParser.parseTRUN_ = function(version, flags, reader) {
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var sampleCount = reader.readUint32();
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// skip "data_offset" if present
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if (flags & 0x000001) { reader.skip(4); }
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// skip "first_sample_flags" if present
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if (flags & 0x000004) { reader.skip(4); }
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var samples = [];
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for (var sampleIndex = 0; sampleIndex < sampleCount; sampleIndex++) {
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/** @type {shaka.text.Mp4VttParser.TimeSegment} */
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var sample = {
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duration: null,
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timeOffset: null
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};
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// read "sample duration" if present
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if (flags & 0x000100) { sample.duration = reader.readUint32(); }
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// skip "sample_size" if present
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if (flags & 0x000200) { reader.skip(4); }
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// skip "sample_flags" if present
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if (flags & 0x000400) {reader.skip(4); }
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// read "sample_time_offset" if present
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if (flags & 0x000800) {
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sample.timeOffset = version == 0 ?
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reader.readUint32() :
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reader.readInt32();
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}
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samples.push(sample);
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}
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return samples;
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};
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/**
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* Parses a vttc box into a cue.
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*
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* @param {!ArrayBuffer} data
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* @param {number} startTime
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* @param {number} endTime
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* @return {shaka.text.Cue}
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* @private
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*/
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shaka.text.Mp4VttParser.parseVTTC_ = function(data, startTime, endTime) {
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var payload;
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var id;
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var settings;
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new shaka.util.Mp4Parser()
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.box('payl', shaka.util.Mp4Parser.allData(function(data) {
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payload = shaka.util.StringUtils.fromUTF8(data);
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}))
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.box('iden', shaka.util.Mp4Parser.allData(function(data) {
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id = shaka.util.StringUtils.fromUTF8(data);
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}))
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.box('sttg', shaka.util.Mp4Parser.allData(function(data) {
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settings = shaka.util.StringUtils.fromUTF8(data);
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}))
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.parse(data);
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if (payload) {
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return shaka.text.Mp4VttParser.assembleCue_(payload,
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id,
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settings,
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startTime,
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endTime);
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} else {
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return null;
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}
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};
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/**
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* Take the individual components that make a cue and create a vttc cue.
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*
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* @param {string} payload
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* @param {?string} id
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* @param {?string} settings
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* @param {number} startTime
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* @param {number} endTime
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* @return {!shaka.text.Cue}
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* @private
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*/
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shaka.text.Mp4VttParser.assembleCue_ = function(payload,
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id,
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settings,
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startTime,
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endTime) {
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var cue = new shaka.text.Cue(
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startTime,
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endTime,
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payload);
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if (id) {
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cue.id = id;
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}
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if (settings) {
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var parser = new shaka.util.TextParser(settings);
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var word = parser.readWord();
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while (word) {
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if (!shaka.text.VttTextParser.parseSetting(cue, word)) {
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shaka.log.warning('VTT parser encountered an invalid VTT setting: ',
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word,
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' The setting will be ignored.');
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}
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parser.skipWhitespace();
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word = parser.readWord();
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}
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}
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return cue;
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};
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shaka.text.TextEngine.registerParser(
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'application/mp4; codecs="wvtt"',
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shaka.text.Mp4VttParser);
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