Digital terrestrial television broadcasting ppt

digital terrestrial television broadcasting technology and system and digital terrestrial television broadcasting equipment
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Dr.AldenCutts,United Kingdom,Teacher
Published Date:23-07-2017
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An Introduction to Digital Terrestrial Television (DTT) Broadcasting September 2004What is DTT ? Analogue Terrestrial Television (Existing) • Analogue TV signals received via aerial or communal aerial broadcast distribution (CABD) Use analogue transmission system for viewing on TV set • Currently four free-to-air TV programme channels in HK Digital Terrestrial Television (Coming) • Digital TV signal received 0 1 1 0 0 1 1 1 0 1 0 1 via aerial or CABD system and decoded for viewing on TV set Use digital transmission • Supports more free-to-air Decoder TV programme channels plus high definition TVHow to receive Digital Terrestrial Television ? How to Receive DTT ? Decoder External decoder added between TV socket and conventional TV set OR Integrated digital TV set with decoder built in 0 1 1 0 0 1 1 1 0 1 0 1ŠŠŠŠŠŠ Benefits of DTT Benefits of DTT Benefits of DTT Improved reception and picture quality Support new services like high definition television (HDTV) and multimedia / interactive services Carry more contents in one channel Support mobile / portable reception Better use of frequency spectrum Release valuable frequency spectrum for other uses after full migration from analogue to digital broadcastingDTT Improves Reception of Television Signals Improves Reception of Television Signals Analogue – weak signal causes snowy pictures Radio signals weaken over distance and due to blockings Digital – clear picture can be received at a lower signal levelDTT Improves Television Picture Quality Improves Television Picture Quality Analogue – multi-path reflections from tall buildings cause ghosting Digital – clear picture and no ghosting Decoder 0111011101DTT Supports High Definition Television Digital TV (High Definition) Analogue TV (Standard Definition) Resolution up to 575 lines Resolution up to 1080 lines (vertical) x 720 pixels (vertical) x 1920 pixels (horizontal) (horizontal) Aspect ratio 4:3 Aspect ratio 16:9 (Widescreen) Stereo sound Multi sound channels (e.g. Dolby 5.1 multi-channel sound)DTT Supports Multi-Channel Programmes and DTT Supports Multi-Channel Programmes and Multimedia Contents Multimedia Contents A frequency channel with digital transmission can Digital carry one high definition TV Digital broadcasting programme channel plus frequency multi-sound channels and Channel data services OR Digital four standard definition TV frequency programme channels plus Channel multi-sound channels and data services A frequency channel with analogue transmission can Analogue carry one standard definition Analogue frequency equivalent TV programme broadcasting Channel channel onlyDTT Supports Reception by Mobile / Portable Devices Analogue – fixed reception only Analogue broadcasting 0 1 1 0 0 1 1 1 0 1 0 1 Digital broadcasting Decoder Digital – fixed and mobile receptionDTT Makes More Efficient Use of Radio Spectrum Multi-Frequency Network Single-Frequency Network (Used by DTT only) (Used by Existing Analogue TV) Channel 30 Channel 21, 23, 25, 27 Channel 34, 38, 42, 44 Temple Hill Castle Peak Temple Hill Castle Peak Cloudy Hill Cloudy Hill Channel 49, 51, 53, 55 • Different transmitters use different • Different transmitters use the same frequency channels to carry the same frequency channel to transmit the TV programme channels same TV programme channels • Many frequency channels are • Only one frequency channel is required to cover the service area required to cover the service areaRelease of Valuable Frequency Spectrum after Analogue Switch-off and Full Migration to Digital Existing Status digital Some spectrum can only be The existing used for digital broadcast (maximum 5 multiplexes) spectrum can be analogue used for transmitting only 4 ATV Home ATV World analogue channels TVB Jade TVB Pearl and some digital channels After Analogue digital broadcasting services digital Switch-off The whole spectrum can be spectrum released used for digital for digital broadcasts and other applications broadcasts and other applicationsTimetable for Implementation of DTT Timetable for Implementation of DTT Analogue Broadcasts Analogue Existing four Only Now free TV programmes Simulcast starts (By 2007) Simultaneous Analogue and Analogue Digital Broadcasts Digital New HDTV Simulcast (Simulcast) and/or multi- Period channel Digital Digital programmes Analogue broadcasts to be switched off Digital Analogue Broadcasts Digital Digital Digital Digital Digital Switch- Only off 12More about DTT in Hong Kong Please visit the following websites for more information about DTT in Hong Kong: 1. Communications and Technology Branch, Commerce, Industry and Technology Bureau (http://www.citb.gov.hk/ctb) 2. Office of the Telecommunications Authority (http://www.ofta.gov.hk)

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