On 04/17/2011 12:45 AM, Charles P. Steinmetz wrote:
John wrote:
IMO, your crack about NTSC is unjustified.
IMO, NTSC color was a very elegant engineering solution to backwards
compatability. Without that, we could well be still watching B&W.
The other contemporary backward-compatible solutions -- PAL and SECAM --
did not suffer from the color drift that plagued color NTSC. So, there
were superior methods of backward-compatible color insertion available
and the FCC still chose the NTSC method. Bad decision, which saddled the
US with inferior broadcast video for 60 years -- just as choosing 8VSB
has done for digital video in the US.
This is why "Never Twice Same Colour" became an alternative expansion of
NTSC. If you look at PAL you will see that it was made more resistive to
multipath phase errors by alternating the polarity of one of the colour
difference signals on every other field, which by interlacing will cause
the opposite turn in the colour spectrum on the next line so on average
they will cancel.
As I recall it, the original choice of colours for the NTSC caused greif
over time and was in practice changed later. A quick check on the NTSC
wikipedia article verifies this.
So NTSC didn't get it all quite right.
Also, stepping from 60 fields per second to 60/1,001 fields per second
still haunts us when PAL stayed at 50 fields per second. For SD-SDI they
where able to match them up to a common 270 MBd, but for HD-SDI we have
1,485 MBd and 1,485/1,001 MBd. This had to be solved with dual
oscillators in the first products, then with a re-synthesis chip and now
there is oscillators with dual frequencies which is good enough. This
1,001 factor also comes into play with some audio production... so this
factor remains with changed underlying TV system.
So some of their particular technology choices isn't a good long term
solution.
NTSC did manage to get a colour solution out of the door, but it wasn't
the best technological solution for its day.
Cheers,
Magnus
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
