shaka-player
Version:
DASH/EME video player library
447 lines (391 loc) • 15.2 kB
JavaScript
/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.cea.Mp4CeaParser');
goog.require('goog.asserts');
goog.require('shaka.cea.CeaUtils');
goog.require('shaka.cea.SeiProcessor');
goog.require('shaka.log');
goog.require('shaka.media.ClosedCaptionParser');
goog.require('shaka.util.DataViewReader');
goog.require('shaka.util.Error');
goog.require('shaka.util.Mp4Parser');
goog.require('shaka.util.Mp4BoxParsers');
/**
* MPEG4 stream parser used for extracting 708 closed captions data.
* @implements {shaka.extern.ICeaParser}
* @export
*/
shaka.cea.Mp4CeaParser = class {
/** */
constructor() {
/**
* SEI data processor.
* @private
* @const {!shaka.cea.SeiProcessor}
*/
this.seiProcessor_ = new shaka.cea.SeiProcessor();
/**
* Map of track id to corresponding timescale.
* @private {!Map<number, number>}
*/
this.trackIdToTimescale_ = new Map();
/**
* Default sample duration, as specified by the TREX box.
* @private {number}
*/
this.defaultSampleDuration_ = 0;
/**
* Default sample size, as specified by the TREX box.
* @private {number}
*/
this.defaultSampleSize_ = 0;
/**
* @private {shaka.cea.Mp4CeaParser.BitstreamFormat}
*/
this.bitstreamFormat_ = shaka.cea.Mp4CeaParser.BitstreamFormat.UNKNOWN;
}
/**
* Parses the init segment. Gets Default Sample Duration and Size from the
* TREX box, and constructs a map of Track IDs to timescales. Each TRAK box
* contains a track header (TKHD) containing track ID, and a media header box
* (MDHD) containing the timescale for the track
* @override
*/
init(initSegment) {
const Mp4Parser = shaka.util.Mp4Parser;
const BitstreamFormat = shaka.cea.Mp4CeaParser.BitstreamFormat;
const trackIds = [];
const timescales = [];
const codecBoxParser = (box) => this.setBitstreamFormat_(box.name);
new Mp4Parser()
.box('moov', Mp4Parser.children)
.box('mvex', Mp4Parser.children)
.fullBox('trex', (box) => {
const parsedTREXBox = shaka.util.Mp4BoxParsers.parseTREX(
box.reader);
this.defaultSampleDuration_ = parsedTREXBox.defaultSampleDuration;
this.defaultSampleSize_ = parsedTREXBox.defaultSampleSize;
})
.box('trak', Mp4Parser.children)
.fullBox('tkhd', (box) => {
goog.asserts.assert(
box.version != null,
'TKHD is a full box and should have a valid version.');
const parsedTKHDBox = shaka.util.Mp4BoxParsers.parseTKHD(
box.reader, box.version);
trackIds.push(parsedTKHDBox.trackId);
})
.box('mdia', Mp4Parser.children)
.fullBox('mdhd', (box) => {
goog.asserts.assert(
box.version != null,
'MDHD is a full box and should have a valid version.');
const parsedMDHDBox = shaka.util.Mp4BoxParsers.parseMDHD(
box.reader, box.version);
timescales.push(parsedMDHDBox.timescale);
})
.box('minf', Mp4Parser.children)
.box('stbl', Mp4Parser.children)
.fullBox('stsd', Mp4Parser.sampleDescription)
// These are the various boxes that signal a codec.
.box('avc1', codecBoxParser)
.box('avc3', codecBoxParser)
.box('dvav', codecBoxParser)
.box('dva1', codecBoxParser)
.box('hev1', codecBoxParser)
.box('hvc1', codecBoxParser)
.box('dvh1', codecBoxParser)
.box('dvhe', codecBoxParser)
.box('vvc1', codecBoxParser)
.box('vvi1', codecBoxParser)
.box('dvc1', codecBoxParser)
.box('dvi1', codecBoxParser)
// This signals an encrypted sample, which we can go inside of to find
// the codec used.
.box('encv', Mp4Parser.visualSampleEntry)
.box('sinf', Mp4Parser.children)
.box('frma', (box) => {
const {codec} = shaka.util.Mp4BoxParsers.parseFRMA(box.reader);
this.setBitstreamFormat_(codec);
})
.parse(initSegment, /* partialOkay= */ true);
// At least one track should exist, and each track should have a
// corresponding Id in TKHD box, and timescale in its MDHD box
if (!trackIds.length|| !timescales.length ||
trackIds.length != timescales.length) {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.TEXT,
shaka.util.Error.Code.INVALID_MP4_CEA);
}
if (this.bitstreamFormat_ == BitstreamFormat.UNKNOWN) {
shaka.log.alwaysWarn(
'Unable to determine bitstream format for CEA parsing!');
}
// Populate the map from track Id to timescale
trackIds.forEach((trackId, idx) => {
this.trackIdToTimescale_.set(trackId, timescales[idx]);
});
}
/**
* Parses each video segment. In fragmented MP4s, MOOF and MDAT come in
* pairs. The following logic gets the necessary info from MOOFs to parse
* MDATs (base media decode time, sample sizes/offsets/durations, etc),
* and then parses the MDAT boxes for CEA-708 packets using this information.
* CEA-708 packets are returned in the callback.
* @override
*/
parse(mediaSegment) {
const Mp4Parser = shaka.util.Mp4Parser;
const BitstreamFormat = shaka.cea.Mp4CeaParser.BitstreamFormat;
if (this.bitstreamFormat_ == BitstreamFormat.UNKNOWN) {
// We don't know how to extract SEI from this.
return [];
}
/** @type {!Array<!shaka.extern.ICeaParser.CaptionPacket>} **/
const captionPackets = [];
let moofOffset = 0;
/** @type {!Array<!shaka.cea.Mp4CeaParser.ParsedTRAF>} */
let parsedTRAFs = [];
new Mp4Parser()
.box('moof', (box) => {
moofOffset = box.start;
// traf box parsing is reset on each moof.
parsedTRAFs = [];
Mp4Parser.children(box);
})
.box('traf', (box) => {
parsedTRAFs.push({
baseMediaDecodeTime: null,
defaultSampleDuration: this.defaultSampleDuration_,
defaultSampleSize: this.defaultSampleSize_,
parsedTRUNs: [],
timescale: shaka.cea.CeaUtils.DEFAULT_TIMESCALE_VALUE,
});
Mp4Parser.children(box);
})
.fullBox('trun', (box) => {
goog.asserts.assert(
box.version != null && box.flags != null,
'TRUN is a full box and should have a valid version & flags.');
const lastTRAF = parsedTRAFs[parsedTRAFs.length - 1];
const parsedTRUN = shaka.util.Mp4BoxParsers.parseTRUN(
box.reader, box.version, box.flags);
lastTRAF.parsedTRUNs.push(parsedTRUN);
})
.fullBox('tfhd', (box) => {
goog.asserts.assert(
box.flags != null,
'TFHD is a full box and should have valid flags.');
const lastTRAF = parsedTRAFs[parsedTRAFs.length - 1];
const parsedTFHD = shaka.util.Mp4BoxParsers.parseTFHD(
box.reader, box.flags);
// If specified, defaultSampleDuration and defaultSampleSize
// override the ones specified in the TREX box
lastTRAF.defaultSampleDuration = parsedTFHD.defaultSampleDuration ||
this.defaultSampleDuration_;
lastTRAF.defaultSampleSize = parsedTFHD.defaultSampleSize ||
this.defaultSampleSize_;
const trackId = parsedTFHD.trackId;
// Get the timescale from the track Id
if (this.trackIdToTimescale_.has(trackId)) {
lastTRAF.timescale = this.trackIdToTimescale_.get(trackId);
}
})
.fullBox('tfdt', (box) => {
goog.asserts.assert(
box.version != null,
'TFDT is a full box and should have a valid version.');
const lastTRAF = parsedTRAFs[parsedTRAFs.length - 1];
const parsedTFDT = shaka.util.Mp4BoxParsers.parseTFDTInaccurate(
box.reader, box.version);
lastTRAF.baseMediaDecodeTime = parsedTFDT.baseMediaDecodeTime;
})
.box('mdat', (box) => {
const offset = moofOffset - box.start - 8;
const initialPosition = box.reader.getPosition();
for (const parsedTRAF of parsedTRAFs) {
if (parsedTRAF.baseMediaDecodeTime === null) {
// This field should have been populated by the Base Media Decode
// Time in the tfdt box.
shaka.log.alwaysWarn(
'Unable to find base media decode time for CEA captions!');
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.TEXT,
shaka.util.Error.Code.INVALID_MP4_CEA);
}
box.reader.seek(initialPosition);
this.parseMdat_(box.reader,
parsedTRAF.baseMediaDecodeTime,
parsedTRAF.timescale,
parsedTRAF.defaultSampleDuration,
parsedTRAF.defaultSampleSize,
offset,
parsedTRAF.parsedTRUNs,
captionPackets);
}
})
.parse(mediaSegment, /* partialOkay= */ false);
return captionPackets;
}
/**
* Parse MDAT box.
* @param {!shaka.util.DataViewReader} reader
* @param {number} time
* @param {number} timescale
* @param {number} defaultSampleDuration
* @param {number} defaultSampleSize
* @param {number} offset
* @param {!Array<shaka.util.ParsedTRUNBox>} parsedTRUNs
* @param {!Array<!shaka.extern.ICeaParser.CaptionPacket>} captionPackets
* @private
*/
parseMdat_(reader, time, timescale, defaultSampleDuration,
defaultSampleSize, offset, parsedTRUNs, captionPackets) {
const BitstreamFormat = shaka.cea.Mp4CeaParser.BitstreamFormat;
const CeaUtils = shaka.cea.CeaUtils;
let sampleIndex = 0;
// The fields in each ParsedTRUNSample contained in the sampleData
// array are nullable. In the case of sample data and sample duration,
// we use the defaults provided by the TREX/TFHD boxes. For sample
// composition time offset, we default to 0.
let sampleSize = defaultSampleSize;
// Combine all sample data. This assumes that the samples described across
// multiple trun boxes are still continuous in the mdat box.
const sampleDatas = parsedTRUNs.map((t) => t.sampleData);
const sampleData = [].concat(...sampleDatas);
if (sampleData.length) {
sampleSize = sampleData[0].sampleSize || defaultSampleSize;
}
reader.skip(offset + parsedTRUNs[0].dataOffset);
while (reader.hasMoreData()) {
const naluSize = reader.readUint32();
const naluHeader = reader.readUint8();
let naluType = null;
let isSeiMessage = false;
let naluHeaderSize = 1;
goog.asserts.assert(this.bitstreamFormat_ != BitstreamFormat.UNKNOWN,
'Bitstream format should have been checked before now!');
switch (this.bitstreamFormat_) {
case BitstreamFormat.H264:
naluType = naluHeader & 0x1f;
isSeiMessage = naluType == CeaUtils.H264_NALU_TYPE_SEI;
break;
case BitstreamFormat.H265:
naluHeaderSize = 2;
reader.skip(1);
naluType = (naluHeader >> 1) & 0x3f;
isSeiMessage =
naluType == CeaUtils.H265_PREFIX_NALU_TYPE_SEI ||
naluType == CeaUtils.H265_SUFFIX_NALU_TYPE_SEI;
break;
case BitstreamFormat.H266:
naluHeaderSize = 2;
reader.skip(1);
naluType = (naluHeader >> 1) & 0x3f;
isSeiMessage =
naluType == CeaUtils.H266_PREFIX_NALU_TYPE_SEI ||
naluType == CeaUtils.H266_SUFFIX_NALU_TYPE_SEI;
break;
default:
return;
}
if (isSeiMessage) {
let timeOffset = 0;
if (sampleIndex < sampleData.length) {
timeOffset = sampleData[sampleIndex].sampleCompositionTimeOffset || 0;
}
const pts = (time + timeOffset) / timescale;
for (const packet of this.seiProcessor_
.process(reader.readBytes(naluSize - naluHeaderSize))) {
captionPackets.push({
packet,
pts,
});
}
} else {
try {
reader.skip(naluSize - naluHeaderSize);
} catch (e) {
// It is necessary to ignore this error because it can break the start
// of playback even if the user does not want to see the subtitles.
break;
}
}
sampleSize -= (naluSize + 4);
if (sampleSize == 0) {
if (sampleIndex < sampleData.length) {
time += sampleData[sampleIndex].sampleDuration ||
defaultSampleDuration;
} else {
time += defaultSampleDuration;
}
sampleIndex++;
if (sampleIndex < sampleData.length) {
sampleSize = sampleData[sampleIndex].sampleSize || defaultSampleSize;
} else {
sampleSize = defaultSampleSize;
}
}
}
}
/**
* @param {string} codec A fourcc for a codec.
* @private
*/
setBitstreamFormat_(codec) {
if (shaka.cea.Mp4CeaParser.CodecBitstreamMap_.has(codec)) {
this.bitstreamFormat_ =
shaka.cea.Mp4CeaParser.CodecBitstreamMap_.get(codec);
}
}
};
/** @enum {number} */
shaka.cea.Mp4CeaParser.BitstreamFormat = {
UNKNOWN: 0,
H264: 1,
H265: 2,
H266: 3,
};
/** @private {Map<string, shaka.cea.Mp4CeaParser.BitstreamFormat>} */
shaka.cea.Mp4CeaParser.CodecBitstreamMap_ = new Map()
// AVC
.set('avc1', shaka.cea.Mp4CeaParser.BitstreamFormat.H264)
.set('avc3', shaka.cea.Mp4CeaParser.BitstreamFormat.H264)
// Dolby Vision based in AVC
.set('dvav', shaka.cea.Mp4CeaParser.BitstreamFormat.H264)
.set('dva1', shaka.cea.Mp4CeaParser.BitstreamFormat.H264)
// HEVC
.set('hev1', shaka.cea.Mp4CeaParser.BitstreamFormat.H265)
.set('hvc1', shaka.cea.Mp4CeaParser.BitstreamFormat.H265)
// Dolby Vision based in HEVC
.set('dvh1', shaka.cea.Mp4CeaParser.BitstreamFormat.H265)
.set('dvhe', shaka.cea.Mp4CeaParser.BitstreamFormat.H265)
// VVC
.set('vvc1', shaka.cea.Mp4CeaParser.BitstreamFormat.H266)
.set('vvi1', shaka.cea.Mp4CeaParser.BitstreamFormat.H266)
// Dolby Vision based in VVC
.set('dvc1', shaka.cea.Mp4CeaParser.BitstreamFormat.H266)
.set('dvi1', shaka.cea.Mp4CeaParser.BitstreamFormat.H266);
/**
* @typedef {{
* baseMediaDecodeTime: ?number,
* defaultSampleDuration: number,
* defaultSampleSize: number,
* parsedTRUNs: !Array<shaka.util.ParsedTRUNBox>,
* timescale: number
* }}
*
* @property {?number} baseMediaDecodeTime
* @property {number} defaultSampleDuration
* @property {number} defaultSampleSize
* @property {!Array<shaka.util.ParsedTRUNBox>} parsedTRUNs
* @property {?number} timescale
*/
shaka.cea.Mp4CeaParser.ParsedTRAF;
shaka.media.ClosedCaptionParser.registerParser('video/mp4',
() => new shaka.cea.Mp4CeaParser());