by Klaas Robers » Wed Apr 18, 2007 6:54 am
The 30 line discs that Denis made are intended for his replicae of Baird Televisors and Daily Express monitors. I think that only if you want to make a "perfect" replica of some vintage equipment, that 30 lines is a reasonable choise.
The disc Denis was punching have indeed the wider rectangular holes and a wider spacing for the first and last 3 lines. When you are doing things perfect, then they should be perfect. The 3:7 aspect ratio implies a more narrow spacing and smaller holes than the 32 line "Club standard".
The 30 line video phragments of the club-CDs have still a 2:3 aspect ratio, there is a much longer black period around the sync pulse. The extra wide lines are indeed anticipated, at least at CD 3. This gives almost the same width as 32 lines, although the borders have less definition. The special 3:7 aspectratio (in practice because of the wider lines and the sync pulse almost 2:1) cannot be experienced.
Another difference is that the 30 line video has no frame identification, while the 32 line video has the missing line pulse. If you want to experiment with automatic frame synchronisation then this cannot be done with the 30 line video.