HD-MAC
HD-MAC is a further development of the MAC process into an analogue HDTV system with 1250 lines, 1152 of which are visible. It was used for test programs in Europe at the beginning of the 1990s . a. at the live broadcast of the 1992 Olympic Games from Barcelona.
The bandwidth and thus the horizontal resolution is doubled compared to the D2-MAC . For reasons of compatibility, however, the line frequency is still 15625 Hertz , so that four partial images are required for a complete image. This gives you three options for vertical resolution when recording:
- 50 images per second with 288 lines for particularly fast image areas,
- 25 frames per second with 576 lines for normally moving image areas or
- 12.5 frames per second with 1152 lines for particularly quiet image areas.
The image is further divided into blocks of 8 × 8 pixels, for each of which the appropriate deinterlacing method is specified.
During playback, the decoder has to digitally store the image and convert it back into 50 or 100 images by reading out the memory several times. For the first time in Europe, the picture format for HDTV cameras and tube TV receivers was 16: 9. HD-MAC signals were backwards compatible with D2-MAC receivers.
The system never appeared in consumer equipment. Although the actual transmission was analog, HD-MAC required a lot of digital technology, which was expensive at the time. In addition, apart from expensive and bulky tube devices and a few, also expensive projectors, no screens were available that could have displayed the HD signal. At the same time, it became apparent that fully digital broadcast technologies such as DVB or ATSC would become available. In addition, the industry had planned a smooth transition from SDTV transmitted via D2-MAC to compatible HDTV via HD-MAC. However, this would have required a larger installed base of D2-MAC receivers, which never came about.
See also
Web link
- Albrecht Gasteiner 1992: HD-MAC = TV future? .