mpeg2 ts content and rates

DVB TransmissionDVB builds upon MPEG-2 and uses MPEG-2 Transmission. It also defines additional private sections andproviding a definition of the physical medium (modulation, coding, etc) needed to carry the MPEG-2Transport Streams.

Typical Streams carried in a DVB Terrestrial Transport Multiplex

Each MPEG-2 MPTS multiplex carries a number of streams which in combination deliver the requiredservices. Here is a sample break-down of the various MPEG-2 streams being used to provide a terrestrial24 Mbps TV multiplex:

Stream bit rate (kbps) SI 300 PSI 546 Digital Teletext 754 Total per Mux 1600

Sample per-multiplex overheads

Stream bit rate (kbps) TV Video * 5000 Stereo Audio 270 SubTitles 50ConditionalAccess 600

TotalProgramme 5920

Bit rate per programme

(* Video at 4-6 Mbps depending on content, Conditional Access may not be required)

This allows a standard 8 MHz channel to carry 5 TV channels or 4 higher quality channels withoutconditional access - or 3 high quality channels with conditional access. The remaining bandwidth may beused for other services such as Electronic Programme Guides (EPGs), Audio Descriptions for the visuallyimpaired (~ 70 kbps), Signing for the deaf (~ 400 kbps using a separate window), house pages, digital data,software down-loads, etc.

DVB Bearer Networks

The DVB standards allows a DVB signal to be carried over a range of bearer networks. Various standardshave evolved which define transmission over particular types of link:

DVB-S (Satellite) ETS 300 421 (Digital Satellite Transmission Systems)DVB-T (Terrestrial) ETS 300 744 ( Digital Terrestrial Transmission Systems)Interfaces to Plesiochronous Digital Hierarchy (PDH) networks (prETS 300 813).Interfaces to Synchronous Digital Hierarchy (SDH) networks (prETS 300 814).Interfaces to Asynchronous Transfer Mode (ATM) networks (prETS 300 815).

dvb transmission https://erg.abdn.ac.uk/future-net/digital-video/dvb-trans.html

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Interfaces for CATV/SMATV Headends and similar Professional Equipment (EN50083-9)

Digital Satellite TV (DVB-S)Satellite transmission has lead the way in delivering digital TV to viewers. A typical satellite channel has36 MHz bandwidth, which may support transmission at up to 35-40 Mbps (assuming delivery to a 0.5mreceiving antenna) using Quadrature Phase Shift Keying (QPSK) modulation.

The video, audio, control data and user data are all formed into fixed sized MPEG-2 transport packets. TheMPEG TS packets are grouped into 8 packet frames (1503 B). The frames do not have any additionalcontrol information, but to enable the receiver to find the start of each frame, the TS-header byte isinverted (0xB8) in the first TS packet of each frame. The frames are then passed through a convolutional(organ-pipe) interleaver to ensure the data follows an approximately random pattern, assuring frequencydispersion of the modulated signal. At the start of each frame, the scrambler is re-initialised.

16 bytes of Reed Solomon (RS) coding are added to each 188 byte transport packet to provide ForwardError Correction (FEC) using a RS(204,188,8) code. For the satellite transmission, the resultant bit streamis then interleaved and convolutional coding is applied. The level of coding ranges from 1/2 to 7/8depending on the intended application and available bandwidth. The digital bit stream is then modulatedusing QPSK modulation.

The complete coding process may be summarised by:

Inverting every 8th Synchronisation byteScrambling the contents of each packetReed-Solomon (RS) coding at 8% overheadInterleaved convolutional coding (the level of coding ranges from 1/2 to 7/8 depending on theintended application)The resulting bit stream is modulated using Quadrature Phase Shift Keying (QPSK).

See also: Broadband Multimedia Satellite Systems

UK Digital Terrestrial TV Network (DVB-T)Legislation passed in 1996, has opened the way to allow new companies to enter the terrestrial TV market,while protecting the interest of the main players. This lead to the granting of licences to various companiesduring 1997, and the planned roll-out of the first direct-to-home digital terrestrial services duringNovember 1998.

In the UK, a standard TV channel is 8 MHz wide, accommodating the TV signal in Phase Alternate Line(PAL) format and the sound subcarrier. The same 8 MHz of bandwidth may be used to provide a 24 Mbpsdigital transmission path using Coded Orthogonal Frequency Division Multiplexing (COFDM) modulation.This may support up to 6 digital TV channels.

The information is transmitted in the following manner:

COFDM or Quadrature Phase Modulation (QPSK) (COFDM uses either 1705 carriers (usuallyknown as '2k'), or 6817 carriers ('8k'))Reed-Solomon (RS) coding at 8% overheadInterleaved convolutional coding (the level of coding depends on the intended application)

Some countries have chosen to use introduce a digital TV service which is based on more robustmodulation, allowing mobile reception of the signal, or to pilot high definition TV - in both cases thebandwidth (number of channels) has been traded.


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The UK will initially be providing 6 terrestrial TV multiplexes. These will be received in various parts ofthe UK. Some areas will receive all the multiplexes, while others will receive only one. Many parts of theUK will not be able initially to receive digital terrestrial TV, although these areas are generally sparselypopulated. Satellite TV will also carry the terrestrial programmes.

Multiplex Coverage (%homes) Programmes 1. BBC 90% BBC1, BBC2, Choice,News24 2. 90% ITV, CH4, ITV2 3. 90% S4C, C5, ... 4. BDB 88% Subscription-based + Home shopping 5. BDB 77% Subscription-based + Home shopping 6. BDB 69% Subscription-based + Home shopping

See also :

MPEG-2MPEG-2 Decoders and EncodersMPEG-2 TransmissionDigital Video Broadcasting (DVB)MPEG-2 and DVB StandardsDVB ReceiversDVB Transmission (this page)Data Transmission & DSM-CCIndex to Digital TV PagesFuture Networks Research


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mpeg2 ts content and rates

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