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HD-MAC was a proposed broadcast television systems standard by the European Commission in 1986 (MAC standard), a part of Eureka 95 project. It was an early attempt by the EEC to provide High-definition television (HDTV) in Europe. It was a complex mix of analogue signal (Multiplexed Analogue Components), multiplexed with digital sound, and assistance data for decoding (DATV). The video signal (1250 (1152 visible) lines/50 fields per second in 16:9 aspect ratio) was encoded with a modified D2-MAC encoder. HD-MAC could be decoded by a standard D2-MAC receivers (SDTV), but in that mode only 625 (576) lines and certain artifacts were visible. To decode the signal in full resolution required a specific HD-MAC tuner. == Formats naming convention == EBU video format description will be used in this article, as follows: width x height (type: i or p ) / number of full frames per second As an example, the 1280×720p/60 format provides 60 1280 pixels wide and 720 pixel high progressively scanned pictures each second. Lines are transmitted in the natural sequence: 1, 2, 3, 4.... European standard definition broadcasts use 720×576i/25, meaning 25 720 pixels wide and 576 pixels high interlaced frames: odd lines (1, 3, 5 ...) are grouped to build the odd field, which is transmitted first, then it is followed by the even field containing lines 2, 4, 6... Thus, there are two fields in a frame, resulting in a field frequency of 25 × 2 = 50 Hz. The visible part of the video signal provided by an HD-MAC receiver was 1152i/25, which exactly doubles the vertical resolution of standard definition. The amount of information is multplied by 4, considering the encoder started its operations from a 1440x1152i/25 sampling grid. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「HD-MAC」の詳細全文を読む スポンサード リンク
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