Quick question. MAC picture quality. Was it as good as HD is now?
Yes, there was HD-MAC with 1250 (625*2) lines with 1152 lines visible so better than our 1080 lines of today.
Hmm - did you actually see any HD-MAC broadcasts ?
It was based on 2048x1152 active samples but based on the 1024x576 D-MAC transmission chain. It used some motion adaption to switch between 288 line resolution at 50Hz 1:1 progressive, 576 line resolution at 25Hz 2:1 interlace and 1152 line resolution at 12.5Hz 4:1 interlace.
This was done on a block-by-block basis, with some basic motion vectoring to try and improve things, with MAC's data-in-blanking system used to carry the information for each block (called Digital Assistance - as this was digital data that assisted in processing the analogue MAC - Multiplexed Analogue Component - video)
The HD-MAC signal was effectively a 16:9 D/D2-MAC signal which could be received by any D or D2-MAC receiver (4:3 displays would centre-cut - letterboxing wasn't an option as it would require a frame store!) - so no requirement for separate SD and HD broadcasts. That was the theory.
However the switching between 288/576/1152 1:1/2:1:/4:1 interlacing on a block-by-block basis made the D-MAC SD picture horrible to watch - and the HD-MAC reconstruction wasn't that great.
Don't get me wrong. The analogue Eureka 1250 pictures looked great (and the 1440x1152 digital video recordings made onto 4xD1 720x576 D1 VTRs looked stunning at the time) The HD-MAC system really didn't do that good a job. It certainly doesn't compare well to a decent H264 1080i or 720p broadcast we get these days. The origination tech was there (though not really practical) The broadcast tech wasn't.
I watched the Barcelona and Albertville Olympics in 16:9 D2-MAC on a modified BSB receiver (the Philips models were massively better quality than the Ferguson or Tatung boxes from memory) feeding a 4:3 RGB display modified to scan crush to 16:9. The blockiness was not pretty. I saw some HD-MAC off-air on a number of occasions - and again it didn't quite deliver.
And in 1992 there is no way the HD production kit was practical.
HOWEVER - D/D2 MAC delivered excellent SD picture quality. Streets ahead of the horribly noisy PAL composite stuff that Sky delivered. (Analogue satellite uses FM modulation which increases noise at higher frequencies. Composite chroma is quite high-frequency and thus the PAL broadcasts on satellite looked quite a lot noisier than VSB terrestrial. Because MAC used time-compression to split luma and chroma - the noise was far less obvious). Compared to MPEG2 SD broadcasts we see now, D-MAC and D2-MAC delivered probably better pictures, though the source material was often lower quality than you'd expect today. BSB had one of the first 16:9 telecines in the UK. Long after BSkyB abandoned BSB's MAC technology, and no longer needed 16:9 transfers, other broadcasters who were 16:9 used the facilities BSkyB had to do 16:9 transfers. (TV1000 which broadcast to Scandinavia from West London used them I believe for movie transfers, as did Channel Four for their Pal+ tests I believe)
