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Encyclopedia > MPEG transport stream
Multiple MPEG programs are combined then sent to a transmitting antenna. In the US broadcast digital TV system, an ATSC receiver then decodes the TS and displays it on your TV...

Transport stream (TS, TP, or MPEG-TS) is a communications protocol for audio, video, and data which is specified in MPEG-2 Part 1, Systems (ISO/IEC standard 13818-1[1]). Its design goal is to allow multiplexing of digital video and audio and to synchronize the output. Transport stream offers features for error correction for transportation over unreliable media, and is used in broadcast applications such as DVB and ATSC. It is contrasted with program stream, designed for more reliable media such as DVDs. Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... Advance Television Systems Committe (ATSC) tuner allows reception of over the air high definition digital television signals in North America and South Korea. ... In the field of telecommunications, a communications protocol is the set of standard rules for data representation, signalling, authentication and error detection required to send information over a communications channel. ... Digital audio comprises audio signals stored in a digital format. ... Digital video is a type of video recording system that works by using a digital, rather than analog, representation of the video signal. ... The Program and System Information Protocol is the protocol used in the ATSC digital television standard for carrying data about each channel. ... MPEG-2 is a standard for the generic coding of moving pictures and associated audio information [1]. It is widely used around the world to specify the format of the digital television signals that are broadcast by terrestrial (over-the-air), cable, and direct broadcast satellite TV systems. ... This article does not cite any references or sources. ... The International Electrotechnical Commission (IEC) is an international standards organization dealing with electrical, electronic and related technologies. ... In telecommunications, multiplexing (also muxing or MUXing) is the combining of two or more information channels onto a common transmission medium using hardware called a multiplexer or (MUX). ... It has been suggested that A/V sync be merged into this article or section. ... It has been suggested that Error-correcting code be merged into this article or section. ... Official DVB logo, found on compliant devices DVB, short for Digital Video Broadcasting, is a suite of internationally accepted, open standards for digital television maintained by the DVB Project, an industry consortium with more than 270 members, and published by a Joint Technical Committee (JTC) of European Telecommunications Standards Institute... Established in 1982, the Advanced Television Systems Committee (ATSC) is the group that developed the ATSC digital television standard for the United States, also adopted by Canada, Mexico, South Korea, and recently Honduras and is being considered by other countries. ... Program stream (PS or MPEG-PS) is a name for the formats specified in MPEG-1 Systems and MPEG-2 Part 1, Systems (ISO/IEC standard 13818-1). ... DVD (Digital Versatile Disc or Digital Video Disc) is an optical disc storage media format that can be used for data storage, including movies with high video and sound quality. ...

Contents

Layers of communication

Similar to the ISO network protocol stack, a transport stream is processed by the receiver in layers. An example stream containing video may be processed as follows: It has been suggested that this article or section be merged with communications protocol. ...

  1. Composition of the various programs.
  2. Packetized Elementary Stream (PES)
  3. Elementary stream (ES) - audio or video (the below is for video only)
  4. Group of pictures (GOP)
  5. Slice—lowest layer that encoder can change DCT coding values to manage bit rate
  6. Macroblock—consisting of 4 DCT blocks
  7. Encoding block or just block—a DCT encoding block, 8x8 luminance pixels

An example of data that is muxed into the transport stream is an electronic program guide. See Program and System Information Protocol for more information. Defined by MPEG communication protocol. ... Defined by MPEG communication protocol. ... In MPEG video encoding, a group of pictures, or GOP, specifies the order in which intra-frames and inter-frames are arranged. ... 2-D DCT compared to the DFT The discrete cosine transform (DCT) is a Fourier-related transform similar to the discrete Fourier transform (DFT), but using only real numbers. ... In telecommunications and computing, bit rate (sometimes written bitrate) is the frequency at which bits are passing a given (physical or metaphorical) point. It is quantified using the bit per second (bit/s) unit. ... Schematic of a 2-to-1 Multiplexer. ... The Sky Digital EPG in the United Kingdom and Republic of Ireland. ... The Program and System Information Protocol is the protocol used in the ATSC digital television standard for carrying data about each channel. ...


Important elements of a transport stream

Packet

A packet is the basic unit of data in a transport stream. It consists of a sync byte, whose value is 0x47, followed by three one-bit flags and a 13-bit PID. This is followed by a 4-bit continuity counter. Additional optional transport fields, as signaled in the optional adaptation field, may follow. The rest of the packet consists of payload. Packets are 188 bytes in length [1] , but the communication medium may add some error correction bytes to the packet. ATSC transmission adds 20 bytes of Reed-Solomon forward error correction to create a packet that is 208 bytes long[2]. The 188-byte packet size was originally chosen for compatibility with ATM systems[3]. In computing a syncword is used to synchronize data. ... This article is about the unit of information. ... Reed-Solomon error correction is a coding scheme which works by first constructing a polynomial from the data symbols to be transmitted and then sending an over-sampled plot of the polynomial instead of the original symbols themselves. ... In telecommunication, forward error correction (FEC) is a system of error control for data transmission, whereby the sender adds redundant data to its messages, which allows the receiver to detect and correct errors (within some bound) without the need to ask the sender for additional data. ... Asynchronous Transfer Mode (ATM) is a cell relay, Circuit switching network and data link layer protocol which encodes data traffic into small (53 bytes; 48 bytes of data and 5 bytes of header information) fixed-sized cells. ...

Partial Transport Stream Packet Format
Name Number
of bits
Description
sync byte 8 0x47
Transport Error Indicator (TEI) 1 Set by demodulator if can't correct errors in the stream[4]
Payload unit start 1 1 means start of PES data
Priority 1
PID 13 Program ID or Packet ID
Scrambling control 2 '00' = Not scrambled
Adaptation field exist 1 1 means presence of the adaptation field
Payload data exist 1 1 means presence of data
Continuity counter 4
Note the sum of the above bits is 32 and is called the Transport Stream 4-byte prefix.
Adaption field 0 or more Depends on flags
Payload Data 0 or more Depends on flags
Adaptation Field Format
Name Number
of bits
Description
Adaptation Field Length 8 Number of bytes in the adaptation field immediately following this byte
Discontinuity indicator 1 Set to 1 if a discontinuity occurred in the continuity counter of the TS packet
Random Access indicator 1 Set to 1 if the PES packet in this TS packet starts a video/audio sequence
Elementary stream priority indicator 1 1 = higher priority
PCR flag 1 1 means adaptation field does contain a PCR field
OPCR flag 1
Splicing point flag 1 1 means presence of splice countdown field in adaptation field
Transport private data flag 1 1 means presence of private data bytes in adaptation field
Adaptation field extension flag 1 1 means presence of adaptation field extension
Below fields are optional variable Depends on flags
PCR 33+9 Program clock reference
OPCR 33+9 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 (may be negative)
stuffing bytes variable

This article is about the unit of information. ... In computing a syncword is used to synchronize data. ... A demodulator is an electronic circuit used to recover the information content from the carrier wave of a signal. ... Defined by MPEG communication protocol. ... In cargo transport, the payload is the valuable contents of the vehicle. ... For other uses, see Data (disambiguation). ... Defined by MPEG communication protocol. ...

PID

Each table or elementary stream in a transport stream is identified by a 13-bit 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. An inverse multiplexer (often abbreviated to inverse mux, imux or demux) allows a data stream to be broken into multiple lower data rate communications links. ... Time-division multiplexing (TDM) is a type of digital or (rarely) analog multiplexing in which two or more signals or bit streams are transferred apparently simultaneously as sub-channels in one communication channel, but physically are taking turns on the channel. ...


Programs

Transport stream has a concept of programs. A single program has a unique PID and the elementary streams associated with that program have the same PID. 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 a particular "channel" merely has to decode the payload of the PID associated with its program. It can discard the contents of all other PIDs. Advance Television Systems Committe (ATSC) tuner allows reception of over the air high definition digital television signals in North America and South Korea. ...


Program Specific Information (PSI)

There are 4 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.


PAT

PAT stands for Program Association Table. The PAT lists PIDs for all PMTs in the stream. TS Packets containing PAT information always have PID 0x0.


PMT

Program Map Tables, or PMTs, contain information about programs. For each program, there is a PMT, with the PMT for each program appearing on its own PID. The PMTs describe which PIDs contain data relevant to the program. PMTs also provide metadata about the streams in their constituent PIDs. For example, if a program contains an MPEG-2 video stream, the PMT will list this PID, describe it as a video stream, and provide the type of video that it contains (in this case, MPEG-2). The PMT may also contain additional descriptors providing data about its constituent streams. MPEG-2 is a standard for the generic coding of moving pictures and associated audio information [1]. It is widely used around the world to specify the format of the digital television signals that are broadcast by terrestrial (over-the-air), cable, and direct broadcast satellite TV systems. ...


PCR

To assist the decoder in presenting programs on time, at the right speed, and with synchronization, programs usually periodically provide a Program Clock Reference, or PCR, on one of the PIDs in the program. This is also known as the master clock. Timing in MPEG2 references this clock, for example the presentation time stamp (PTS) is relative to the PCR.


Null packets

Some transmission schemes, such as those in ATSC and DVB, impose strict constant bitrate requirements on the transport stream. In order to ensure that the stream maintains a constant bitrate, a Multiplexer may need to insert some additional packets. The PID 0x1FFF is reserved for this purpose. The payload of null packets may contain any data at all, and the receiver is expected to ignore its contents. Established in 1982, the Advanced Television Systems Committee (ATSC) is the group that developed the ATSC digital television standard for the United States, also adopted by Canada, Mexico, South Korea, and recently Honduras and is being considered by other countries. ... Official DVB logo, found on compliant devices DVB, short for Digital Video Broadcasting, is a suite of internationally accepted, open standards for digital television maintained by the DVB Project, an industry consortium with more than 270 members, and published by a Joint Technical Committee (JTC) of European Telecommunications Standards Institute... Schematic of a 2-to-1 Multiplexer. ...


References

  1. ^ (2000-12-01) ISO/IEC 13818-1 Second edition, page xi or 11 according to PDF viewer. 

See also

Advance Television Systems Committe (ATSC) tuner allows reception of over the air high definition digital television signals in North America and South Korea. ... Official DVB logo, found on compliant devices DVB, short for Digital Video Broadcasting, is a suite of internationally accepted, open standards for digital television maintained by the DVB Project, an industry consortium with more than 270 members, and published by a Joint Technical Committee (JTC) of European Telecommunications Standards Institute... Defined by MPEG communication protocol. ... IPTV (Internet Protocol Television) is a system where a digital television service is delivered by using Internet Protocol over a network infrastructure, which may include delivery by a broadband connection. ... MPEG-2 is a standard for the generic coding of moving pictures and associated audio information [1]. It is widely used around the world to specify the format of the digital television signals that are broadcast by terrestrial (over-the-air), cable, and direct broadcast satellite TV systems. ... Defined by MPEG communication protocol. ... The Program and System Information Protocol is the protocol used in the ATSC digital television standard for carrying data about each channel. ... // The Unidirectional Lightweight Encapsulation (ULE) is a protocol for the transportation of network layer packets over MPEG-2 Transport Streams. ...

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