Wikipedia
HD-MAC
HD-MAC is a proposed broadcast television systems standard by the European Commission in 1986 ( MAC standard), a part of Eureka 95 project. It is an early attempt by the EEC to provide High-definition television (HDTV) in Europe. It is 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.