shaka-player
Version:
DASH/EME video player library
500 lines (453 loc) • 14.2 kB
JavaScript
/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.util.TsParser');
goog.require('goog.asserts');
goog.require('shaka.log');
goog.require('shaka.util.Id3Utils');
goog.require('shaka.util.Uint8ArrayUtils');
/**
* @see https://en.wikipedia.org/wiki/MPEG_transport_stream
* @export
*/
shaka.util.TsParser = class {
/** */
constructor() {
/** @private {?number} */
this.pmtId_ = null;
/** @private {boolean} */
this.pmtParsed_ = false;
/** @private {?number} */
this.videoStartTime_ = null;
/** @private {?number} */
this.videoPid_ = null;
/** @private {?string} */
this.videoCodec_ = null;
/** @private {!Array.<Uint8Array>} */
this.videoData_ = [];
/** @private {?number} */
this.audioStartTime_ = null;
/** @private {?number} */
this.audioPid_ = null;
/** @private {?string} */
this.audioCodec_ = null;
/** @private {!Array.<Uint8Array>} */
this.audioData_ = [];
/** @private {?number} */
this.id3Pid_ = null;
/** @private {!Array.<Uint8Array>} */
this.id3Data_ = [];
}
/**
* Parse the given data
*
* @param {Uint8Array} data
* @return {!shaka.util.TsParser}
*/
parse(data) {
const timescale = shaka.util.TsParser.Timescale_;
const packetLength = shaka.util.TsParser.PacketLength_;
// A TS fragment should contain at least 3 TS packets, a PAT, a PMT, and
// one PID.
if (data.length < 3 * packetLength) {
return this;
}
const syncOffset = Math.max(0, shaka.util.TsParser.syncOffset(data));
const length = data.length - (data.length + syncOffset) % packetLength;
let unknownPIDs = false;
// loop through TS packets
for (let start = syncOffset; start < length; start += packetLength) {
if (data[start] === 0x47) {
const payloadUnitStartIndicator = !!(data[start + 1] & 0x40);
// pid is a 13-bit field starting at the last 5 bits of TS[1]
const pid = ((data[start + 1] & 0x1f) << 8) + data[start + 2];
const adaptationFieldControl = (data[start + 3] & 0x30) >> 4;
// if an adaption field is present, its length is specified by the
// fifth byte of the TS packet header.
let offset;
if (adaptationFieldControl > 1) {
offset = start + 5 + data[start + 4];
// continue if there is only adaptation field
if (offset === start + packetLength) {
continue;
}
} else {
offset = start + 4;
}
switch (pid) {
case 0:
if (payloadUnitStartIndicator) {
offset += data[offset] + 1;
}
this.pmtId_ = this.getPmtId_(data, offset);
break;
case 17:
case 0x1fff:
break;
case this.pmtId_: {
if (payloadUnitStartIndicator) {
offset += data[offset] + 1;
}
const parsedPIDs = this.parsePMT(data, offset);
// only update track id if track PID found while parsing PMT
// this is to avoid resetting the PID to -1 in case
// track PID transiently disappears from the stream
// this could happen in case of transient missing audio samples
// for example
// NOTE this is only the PID of the track as found in TS,
// but we are not using this for MP4 track IDs.
if (this.videoPid_ == null) {
this.videoPid_ = parsedPIDs.video;
this.videoCodec_ = parsedPIDs.videoCodec;
}
if (this.audioPid_ == null) {
this.audioPid_ = parsedPIDs.audio;
this.audioCodec_ = parsedPIDs.audioCodec;
}
if (this.id3Pid_ == null) {
this.id3Pid_ = parsedPIDs.id3;
}
if (unknownPIDs && !this.pmtParsed_) {
shaka.log.debug('reparse from beginning');
unknownPIDs = false;
// we set it to -188, the += 188 in the for loop will reset
// start to 0
start = syncOffset - packetLength;
}
this.pmtParsed_ = true;
break;
}
case this.videoPid_: {
const videoData = data.subarray(offset, start + packetLength);
if (this.videoStartTime_ == null) {
const pes = this.parsePES(videoData);
if (pes && pes.pts != null) {
this.videoStartTime_ = pes.pts / timescale;
}
}
this.videoData_.push(videoData);
break;
}
case this.audioPid_: {
const audioData = data.subarray(offset, start + packetLength);
if (this.audioStartTime_ == null) {
const pes = this.parsePES(audioData);
if (pes && pes.pts != null) {
this.audioStartTime_ = pes.pts / timescale;
}
}
this.audioData_.push(audioData);
break;
}
case this.id3Pid_:
this.id3Data_.push(data.subarray(offset, start + packetLength));
break;
default:
unknownPIDs = true;
break;
}
} else {
shaka.log.warning('Found TS packet that do not start with 0x47');
}
}
return this;
}
/**
* Get the PMT ID from the PAT
*
* @param {Uint8Array} data
* @param {number} offset
* @return {number}
* @private
*/
getPmtId_(data, offset) {
// skip the PSI header and parse the first PMT entry
return ((data[offset + 10] & 0x1f) << 8) | data[offset + 11];
}
/**
* Parse PMT
*
* @param {Uint8Array} data
* @param {number} offset
* @return {!shaka.util.TsParser.PMT}
*/
parsePMT(data, offset) {
const result = {
audio: -1,
video: -1,
id3: -1,
audioCodec: '',
videoCodec: '',
};
const sectionLength = ((data[offset + 1] & 0x0f) << 8) | data[offset + 2];
const tableEnd = offset + 3 + sectionLength - 4;
// to determine where the table is, we have to figure out how
// long the program info descriptors are
const programInfoLength =
((data[offset + 10] & 0x0f) << 8) | data[offset + 11];
// advance the offset to the first entry in the mapping table
offset += 12 + programInfoLength;
while (offset < tableEnd) {
const pid = ((data[offset + 1] & 0x1f) << 8) | data[offset + 2];
switch (data[offset]) {
// SAMPLE-AES AAC
case 0xcf:
break;
// ISO/IEC 13818-7 ADTS AAC (MPEG-2 lower bit-rate audio)
case 0x0f:
if (result.audio === -1) {
result.audio = pid;
result.audioCodec = 'aac';
}
break;
// Packetized metadata (ID3)
case 0x15:
if (result.id3 === -1) {
result.id3 = pid;
}
break;
// SAMPLE-AES AVC
case 0xdb:
break;
// ITU-T Rec. H.264 and ISO/IEC 14496-10 (lower bit-rate video)
case 0x1b:
if (result.video === -1) {
result.video = pid;
result.videoCodec = 'avc';
}
break;
// ISO/IEC 11172-3 (MPEG-1 audio)
// or ISO/IEC 13818-3 (MPEG-2 halved sample rate audio)
case 0x03:
case 0x04:
if (result.audio === -1) {
result.audio = pid;
result.audioCodec = 'mp3';
}
break;
// HEVC
case 0x24:
if (result.video === -1) {
result.video = pid;
result.videoCodec = 'hvc';
}
break;
default:
// shaka.log.warning('Unknown stream type:', data[offset]);
break;
}
// move to the next table entry
// skip past the elementary stream descriptors, if present
offset += (((data[offset + 3] & 0x0f) << 8) | data[offset + 4]) + 5;
}
return result;
}
/**
* Parse PES
*
* @param {Uint8Array} data
* @return {?shaka.util.TsParser.PES}
*/
parsePES(data) {
const startPrefix = (data[0] << 16) | (data[1] << 8) | data[2];
// In certain live streams, the start of a TS fragment has ts packets
// that are frame data that is continuing from the previous fragment. This
// is to check that the pes data is the start of a new pes data
if (startPrefix !== 1) {
return null;
}
/** @type {shaka.util.TsParser.PES} */
const pes = {
data: new Uint8Array(0),
// get the packet length, this will be 0 for video
packetLength: 6 + ((data[4] << 8) | data[5]),
pts: null,
dts: null,
};
// PES packets may be annotated with a PTS value, or a PTS value
// and a DTS value. Determine what combination of values is
// available to work with.
const ptsDtsFlags = data[7];
// PTS and DTS are normally stored as a 33-bit number. Javascript
// performs all bitwise operations on 32-bit integers but javascript
// supports a much greater range (52-bits) of integer using standard
// mathematical operations.
// We construct a 31-bit value using bitwise operators over the 31
// most significant bits and then multiply by 4 (equal to a left-shift
// of 2) before we add the final 2 least significant bits of the
// timestamp (equal to an OR.)
if (ptsDtsFlags & 0xC0) {
// the PTS and DTS are not written out directly. For information
// on how they are encoded, see
// http://dvd.sourceforge.net/dvdinfo/pes-hdr.html
pes.pts =
(data[9] & 0x0e) * 536870912 + // 1 << 29
(data[10] & 0xff) * 4194304 + // 1 << 22
(data[11] & 0xfe) * 16384 + // 1 << 14
(data[12] & 0xff) * 128 + // 1 << 7
(data[13] & 0xfe) / 2;
pes.dts = pes.pts;
if (ptsDtsFlags & 0x40) {
pes.dts =
(data[14] & 0x0e) * 536870912 + // 1 << 29
(data[15] & 0xff) * 4194304 + // 1 << 22
(data[16] & 0xfe) * 16384 + // 1 << 14
(data[17] & 0xff) * 128 + // 1 << 7
(data[18] & 0xfe) / 2;
}
}
// the data section starts immediately after the PES header.
// pes_header_data_length specifies the number of header bytes
// that follow the last byte of the field.
pes.data = data.subarray(9 + data[8]);
return pes;
}
/**
* Return the ID3 metadata
*
* @return {!Array.<shaka.extern.ID3Metadata>}
*/
getMetadata() {
const timescale = shaka.util.TsParser.Timescale_;
const Uint8ArrayUtils = shaka.util.Uint8ArrayUtils;
const metadata = [];
let prevId3Data = new Uint8Array(0);
// parsePES() only works if the data begins on a PES boundary.
// Try the last data blob first, and if it doesn't begin on a
// PES boundary, prepend the previous blob and try again.
// This way, a successful parse will always begin and end on
// the correct boundary, and no data will be skipped.
for (let i = this.id3Data_.length - 1; i >= 0; i--) {
const data = this.id3Data_[i];
goog.asserts.assert(data, 'We should have a data');
const id3Data = Uint8ArrayUtils.concat(data, prevId3Data);
const pes = this.parsePES(id3Data);
if (pes) {
metadata.unshift({
cueTime: pes.pts ? pes.pts / timescale : null,
data: pes.data,
frames: shaka.util.Id3Utils.getID3Frames(pes.data),
dts: pes.dts,
pts: pes.pts,
});
prevId3Data = new Uint8Array(0);
} else {
prevId3Data = id3Data;
}
}
return metadata;
}
/**
* Return the start time for the audio and video
*
* @return {{audio: ?number, video: ?number}}
*/
getStartTime() {
return {
audio: this.audioStartTime_,
video: this.videoStartTime_,
};
}
/**
* Return the audio and video codecs
*
* @return {{audio: ?string, video: ?string}}
*/
getCodecs() {
return {
audio: this.audioCodec_,
video: this.videoCodec_,
};
}
/**
* Check if the passed data corresponds to an MPEG2-TS
*
* @param {Uint8Array} data
* @return {boolean}
*/
static probe(data) {
const syncOffset = shaka.util.TsParser.syncOffset(data);
if (syncOffset < 0) {
return false;
} else {
if (syncOffset > 0) {
shaka.log.warning('MPEG2-TS detected but first sync word found @ ' +
'offset ' + syncOffset + ', junk ahead ?');
}
return true;
}
}
/**
* Returns the synchronization offset
*
* @param {Uint8Array} data
* @return {number}
*/
static syncOffset(data) {
const packetLength = shaka.util.TsParser.PacketLength_;
// scan 1000 first bytes
const scanwindow = Math.min(1000, data.length - 3 * packetLength);
let i = 0;
while (i < scanwindow) {
// a TS fragment should contain at least 3 TS packets, a PAT, a PMT, and
// one PID, each starting with 0x47
if (data[i] === 0x47 &&
data[i + packetLength] === 0x47 &&
data[i + 2 * packetLength] === 0x47) {
return i;
} else {
i++;
}
}
return -1;
}
};
/**
* @const {number}
* @private
*/
shaka.util.TsParser.PacketLength_ = 188;
/**
* @const {number}
* @private
*/
shaka.util.TsParser.Timescale_ = 90000;
/**
* @typedef {{
* audio: number,
* video: number,
* id3: number,
* audioCodec: string,
* videoCodec: string
* }}
*
* @summary PMT.
* @property {number} audio
* Audio PID
* @property {number} video
* Video PID
* @property {number} id3
* ID3 PID
* @property {string} audioCodec
* Audio codec
* @property {string} videoCodec
* Video codec
*/
shaka.util.TsParser.PMT;
/**
* @typedef {{
* data: Uint8Array,
* packetLength: number,
* pts: ?number,
* dts: ?number
* }}
*
* @summary PES.
* @property {Uint8Array} data
* @property {number} packetLength
* @property {?number} pts
* @property {?number} dts
*/
shaka.util.TsParser.PES;