The Design Of The Teletext Decoder

Teletext is a standard by which words and simple pictures can be transmitted intelevision signal channel without more bandwidth. According to teletext standard,television service suppliers could supply TV navigation information, living convenientinformation, on-line news and advertisement and so on.In this thesis, according to EN ETSI300707(V1.2.1), it discuss how to decodeteletext signal in analog television system, and it explain how to integrate decoder insystem. Character replacing function and store format is innovative.The main items are as follows:1. Analysed background and research value of teletext decoder. Introducedteletext decoder research current situation of domestic and abroad. Studied indepth of teletext level1.5in EN ETSI300706(V1.2.1). Introduced teletextsignal transmit format in a television H-line. Described encode way of eacheach teletext packet refer to E N ETSI300706(V1.2.1). Explained contents ineach packet and analysed these contents are useful or not. After analysedrelation between packet and information in packets, the thesis gave everypacket’s sphere of influence.2. Method of realization of teletext decode is described in detail in the thesis. Frist,structure of teletext decode is described in detail. Decode process and decodemethod were decribed. Data stream flow between sub-modules was showed inthe article. According to encode method and information usage of each packet,decode procedure of each packet is designed in packet-decode sub-module.Discussed decode and modify algorithm under3encode mode in teletextstandard. In data-analysis sub-module, analysis method of data what isoutputted from packet-decode sub-module is introduced, and transaction ofpacket26which use for character replace is introduced in detail. Timing of keysignal was demonstrated when data-analysis sub-module was explaining. Instore-control sub-module, stroe position, store sequence and store timing aredescribed. A table listed partition of memory space about teletext data. Algorithm of loop-store page was designed for stroeing teletext page whenuser changed display page number.3. Simulation result of decode is demonstrated. Simulation environment and toolswas also listed in the thesis. Simulation waves were cut off and explanation ofthese waves is given.4. At last, teletext decoder integration in television was discussed. A structurefigure of television which includes teletext decoder was shown. Suggestion ofa sample module which was used for sampling teletext0/1non-reture-to-zerobinary from sinusoidal was made. Summarized the thesis and look ahead ofteletext decode developing.