MPEG transport stream
Filename extension |
.ts, .tsv, .tsa, .m2t[1] |
---|---|
Internet media type |
video/MP2T TOD |
Standard | ISO/IEC 13818-1, ITU-T Recommendation H.222.0[4] |
Open format? | Yes |
Free format? | Yes[5] |
MPEG transport stream (
Transport stream specifies a container format encapsulating
Transport streams differ from the similarly named MPEG program stream in several important ways: program streams are designed for reasonably reliable media, such as discs (like DVDs), while transport streams are designed for less reliable transmission, namely terrestrial or satellite broadcast. Further, a transport stream may carry multiple programs.
Transport stream is specified in
Overview
A transport stream encapsulates a number of other substreams, often
Each stream is chopped into (at most) 188-byte sections and interleaved together. Due to the tiny packet size, streams can be interleaved with less latency and greater error resilience compared to
Transport streams tend to be broadcast as constant bitrate (CBR) and filled with padding bytes when not enough data exists.[a]
Elements
Packet
A network packet is the basic unit of data in a transport stream, and a transport stream is merely a sequence of packets. Each packet starts with a sync byte and a header, that may be followed with optional additional headers; the rest of the packet consists of payload. All header fields are read as big-endian. Packets are 188 bytes in length, but the communication medium may add additional information.[b] The 188-byte packet size was originally chosen for compatibility with Asynchronous Transfer Mode (ATM) systems.[8][9]
Name | Number of bits | big-endian )
|
Description |
---|---|---|---|
4-byte Transport Stream Header | |||
Sync byte
|
8 | 0xff000000
|
Bit pattern of 0x47 (ASCII char 'G') |
Transport error indicator (TEI) | 1 | 0x800000
|
Set when a demodulator can't correct errors from FEC data; indicating the packet is corrupt.[10]
|
Payload unit start indicator (PUSI) | 1 | 0x400000
|
Set when this packet contains the first byte of a new payload unit. For PSI packet data, the first byte of the payload will indicate where this new payload unit starts. For PES packet data, the new PES packet shall start at the start of the payload.[11]
This field allows a receiver that started reading mid transmission to know when it can start extracting data. |
Transport priority | 1 | 0x200000
|
Set when the current packet has a higher priority than other packets with the same PID. |
PID | 13 | 0x1fff00
|
Packet Identifier, describing the payload data. |
Transport scrambling control (TSC) | 2 | 0xc0
|
'00' = Not scrambled.
For '01' (0x40) = Reserved for future use '10' (0x80) = Scrambled with even key '11' (0xC0) = Scrambled with odd key |
Adaptation field control | 2 | 0x30
|
01 – no adaptation field, payload only, 10 – adaptation field only, no payload, |
Continuity counter | 4 | 0xf
|
Sequence number of payload packets (0x00 to 0x0F) within each stream (except PID 8191) Incremented per-PID, only when a payload flag is set. |
Optional fields | |||
Adaptation field | variable | Present if adaptation field control is 10 or 11. See below for format. | |
Payload data | variable | Present if adaptation field control is 01 or 11. Payload may be PES packets, program specific information (below), or other data. |
Name | Number of bits | Bitmask | Description |
---|---|---|---|
Adaptation field length | 8 | Number of bytes in the adaptation field immediately following this byte | |
Discontinuity indicator | 1 | 0x80
|
Set if current TS packet is in a discontinuity state with respect to either the continuity counter or the program clock reference |
Random access indicator | 1 | 0x40
|
Set when the stream may be decoded without errors from this point |
Elementary stream priority indicator
|
1 | 0x20
|
Set when this stream should be considered "high priority" |
PCR flag | 1 | 0x10
|
Set when PCR field is present |
OPCR flag | 1 | 0x08
|
Set when OPCR field is present |
Splicing point flag | 1 | 0x04
|
Set when splice countdown field is present |
Transport private data flag | 1 | 0x02
|
Set when transport private data is present |
Adaptation field extension flag | 1 | 0x01
|
Set when adaptation extension data is present |
Optional fields | |||
PCR | 48 | Program clock reference, stored as 33 bits base, 6 bits reserved, 9 bits extension. The value is calculated as base * 300 + extension. | |
OPCR | 48 | Original Program clock reference. Helps when one TS is copied into another | |
Splice countdown | 8 | Indicates how many TS packets from this one a splicing point occurs (Two's complement signed; may be negative) | |
Transport private data length | 8 | The length of the following field | |
Transport private data | variable | Private data | |
Adaptation extension | variable | See below | |
Stuffing bytes | variable | Always 0xFF
|
Name | Number of bits | Bitmask | Description |
---|---|---|---|
Adaptation extension length | 8 | 0xff00
|
The length of the header |
Legal time window (LTW) flag | 1 | 0x0080
|
|
Piecewise rate flag | 1 | 0x0040
|
|
Seamless splice flag | 1 | 0x0020
|
|
Reserved | 5 | 0x001f
|
|
Optional fields | |||
LTW flag set (2 bytes) | |||
LTW valid flag | 1 | 0x8000
|
|
LTW offset | 15 | 0x7fff
|
Extra information for rebroadcasters to determine the state of buffers when packets may be missing. |
Piecewise flag set (3 bytes) | |||
Reserved | 2 | 0xc00000
|
|
Piecewise rate | 22 | 0x3fffff
|
The rate of the stream, measured in 188-byte packets, to define the end-time of the LTW. |
Seamless splice flag set (5 bytes) | |||
Splice type | 4 | 0xf000000000
|
Indicates the parameters of the H.262 splice. |
DTS next access unit | 36 | 0x0efffefffe
|
The PES DTS of the splice point. Split up as multiple fields, 1 marker bit (0x1), 15 bits, 1 marker bit, 15 bits, and 1 marker bit, for 33 data bits total. |
Name | Number of bits | Bitmask | Description |
---|---|---|---|
Payload Pointer (optional) | 8 | 0xff | Present only if the Payload Unit Start Indicator (PUSI) flag is set, and the packet data type is PSI (not PES).
It gives the index after this byte at which the new payload unit starts. Any payload byte before the index is part of the previous payload unit. |
Actual Payload | variable | The content of the payload. |
Packet identifier (PID)
Each table or elementary stream in a transport stream is identified by a 13-bit packet identifier (PID). A demultiplexer extracts elementary streams from the transport stream in part by looking for packets identified by the same PID. In most applications, time-division multiplexing will be used to decide how often a particular PID appears in the transport stream.
Decimal | Hexadecimal | Description |
---|---|---|
0 | 0x0000 | Program association table (PAT) contains a directory listing of all program map tables |
1 | 0x0001 | Conditional access table (CAT) contains a directory listing of all ITU-T Rec. H.222 entitlement management message streams used by program map tables |
2 | 0x0002 | Transport stream description table (TSDT) contains descriptors relating to the overall transport stream |
3 | 0x0003 | IPMP control information table contains a directory listing of all ISO/IEC 14496-13 control streams used by program map tables |
4–15 | 0x0004-0x000F | Reserved for future use |
16–31 | 0x0010-0x001F | Used by
|
32-8186 | 0x0020-0x1FFA | May be assigned as needed to program map tables, elementary streams and other data tables |
8187 | 0x1FFB | Used by ATSC MGT metadata
|
8188–8190 | 0x1FFC-0x1FFE | May be assigned as needed to program map tables, elementary streams and other data tables |
8191 | 0x1FFF | Null Packet (used for fixed bandwidth padding) |
Programs
Transport stream has a concept of programs. Every program is described by a program map table (PMT). The elementary streams associated with that program have PIDs listed in the PMT. Another PID is associated with the PMT itself. For instance, a transport stream used in digital television might contain three programs, to represent three television channels. Suppose each channel consists of one video stream, one or two audio streams, and any necessary metadata. A receiver wishing to decode one of the three channels merely has to decode the payloads of each PID associated with its program. It can discard the contents of all other PIDs. A transport stream with more than one program is referred to as a multi-program transport stream (MPTS). A single program transport stream is referred to as a single-program transport stream (SPTS).
Program specific information
There are 4 program specific information (PSI) tables: program association (PAT), program map (PMT), conditional access (CAT), and network information (NIT). The MPEG-2 specification does not specify the format of the CAT and NIT.
PCR
To enable a decoder to present synchronized content, such as audio tracks matching the associated video, at least once each 100 ms, a program clock reference (PCR) is transmitted in the adaptation field of an MPEG-2 transport stream packet. The PID with the PCR for an MPEG-2 program is identified by the pcr_pid value in the associated PMT. The value of the PCR, when properly used, is employed to generate a system_timing_clock in the decoder. The system time clock (STC) decoder, when properly implemented, provides a highly accurate time base that is used to synchronize audio and video elementary streams. Timing in MPEG-2 references this clock. For example, the
Null packets
Some transmission schemes, such as those in
Use in digital video cameras
Transport Stream was originally designed for broadcast. Later it was adapted for use with digital video cameras, recorders and players by adding a 4-byte timecode (TC) field to the standard 188-byte packets, resulting in a 192-byte packet.
Use in Blu-ray
Blu-ray Disc video titles authored with menu support are in the
There is also the BDAV (Blu-ray Disc Audio/Visual) format, the consumer-oriented alternative to the BDMV format used for movie releases. The BDAV format is used on Blu-ray Disc recordable for audio/video recording.[22][d] Blu-ray Disc employs the MPEG-2 transport stream recording method. This enables transport streams of a BDAV converted digital broadcast to be recorded as they are with minimal alteration of the packets.[17] It also enables simple stream cut style editing of a BDAV converted digital broadcast that is recorded as is and where the data can be edited just by discarding unwanted packets from the stream. Although it is quite natural, a function for high-speed and easy-to-use retrieval is built in.[17][24]
See also
- MPEG media transport (MMT)
- Real-time Transport Protocol (RTP)
- Unidirectional Lightweight Encapsulation (ULE)
Notes
- ^ The Blu-ray format does not require CBR.
- format prefixes packets with a 4-byte copyright and timestamp tag.
- ^ Possibly an abbreviation for "Transport stream on disc".
- ^ Filename extension .m2ts is used on Blu-ray Disc video files which contain an incompatible BDAV MPEG-2 transport stream due to the four additional octets added to every packet.[16][23]
References
- ^ "TVNT.net - Le forum de la TNT • [Topic Unique] Akira DHB-B31HDR - Double tuner enregistreur TNT HD - MKV - DIVX - DTS : Les adaptateurs pour recevoir la TNT gratuite en SD ou HD". www.tvnt.net.
- .
- Apple Inc.
- ^ a b c ITU-T (October 2014). "Recommendation H.222.0 (10/14)".
- ^ MPEG-2 Encoding Family (Full draft). Sustainability of Digital Formats. Washington, D.C.: Library of Congress. 14 February 2012. Retrieved 13 December 2021.
Licenses pertain to tools and not to streams or files per se.
- ^ "MPEG-2 Transport Stream". AfterDawn.com. Retrieved 8 June 2010.
- ^ "ATSC transmission". Broadcastengineering.com. 20 June 2005. Retrieved 17 May 2012.
- ^ "MPEG Systems FAQ". Mpeg.chiariglione.org. Retrieved 17 May 2012.
- ^ "ATSC MPEG Transport Stream Monitor". Tek.com. Retrieved 17 May 2012.
- ^ "TSReader". Coolstf.com. 7 April 2008. Archived from the original on 27 March 2010. Retrieved 17 May 2012.
- ^ "Information technology – Generic coding of moving pictures and associated audio information: systems". February 2000.
- ^ "Standards – DVB" (PDF). Dvb.org. Archived from the original (PDF) on 13 March 2011. Retrieved 11 September 2012.
- ^ Fairhurst, Gorry. "MPEG-2 Transmission". Archived from the original on 13 August 2017. Retrieved 30 November 2018.
- ^ "5.1.3 Coding of PID and table_id fields". Digital Video Broadcasting (DVB); Specification for Service Information (SI) in DVB systems (PDF). EN. Vol. 300 468 (v1.13.1 ed.). 2012. p. 20. Retrieved 13 October 2016.
{{cite book}}
:|website=
ignored (help) - ^ A Guide to MPEG Fundamentals and Protocol Analysis (PDF), Tektronix, p. 37, retrieved 23 April 2020
- ^ a b c BD ROM – Audio Visual Application Format Specifications (PDF), Blu-ray Disc Association, March 2005, pp. 15–16, archived from the original (PDF) on 3 November 2020, retrieved 26 July 2009
- ^ a b c BD-RE – Audiovisual Application Format Specification for BD-RE 2.1 (PDF), Blu-ray Disc Association, March 2008, archived from the original (PDF) on 6 February 2009
- ^ "Steve Mullen, M2TS primer". Dvinfo.net.
- ^ "Working with JVC Everio MOD & TOD files". Archived from the original on 23 October 2008.
- ^ "How MPEG-TS works". Forum.videohelp.com. Retrieved 17 May 2012.[self-published source?]
- ^ Afterdawn.com Glossary – BD-MV (Blu-ray Movie) and BDAV container Archived 18 February 2009 at the Wayback Machine, Retrieved on 26 July 2009
- ^ a b Afterdawn.com Glossary – BDAV container, Retrieved on 26 July 2009
- ^ Videohelp.com What is Blu-ray Disc and HD DVD? Archived 24 December 2009 at the Wayback Machine, Retrieved on 26 July 2009
- ^ Blu-ray Disc Association (August 2004) Blu-ray Disc Format, White paper (PDF) Page 22, Retrieved on 28 July 2009
External links
- ITU-T H.222.0 | ISO/IEC 13818-1 Systems Spec Documents
- Latest free copy of the spec, August 2018
- MPEG-4 Systems FAQ
- TSDuck – Free open-source tool to manipulate MPEG transport streams.