Posted Fri Aug 06, 2021 4:55 pm
Yeah, so for years everyone was calculating the square pixel screen size as 768 x 576 which would then match the non-square pixel format of 720 x 576. Some bright spark in the broadcast industry realised that digital SD actually has a bigger raster display to that of analog SD and there was an error occurring in some calculations. You can see this effect with the small vertical black bars to the left and right of the picture.
These black bars are only a few pixels wide, but were not being included in the calculation when going from non-square to square pixels. The corrected result ended up as 788 x 576 for a digital square pixel screen size.
But it took Adobe and other creative products a few years to update their presets. I learnt all this from a technical paper that the BBC put out in the early naughties. Not sure if it originated elsewhere first.