> And now, with DVDs, it is seems that we are back to square one and for the
> flimsiest of reasons!
The reason for the difference is because different parts of the world have
different video standards that were in place long before VCR's or DVD
players were even dreamed of. The principal two standarda are PAL and NTSC,
the former being used in Europe, Australia, and South Africa, and NTSC being
the standard for North America, Japan, and the Philippines.
The NTSC (National Television Standards Committee) developed their set of
standard protocols for television broadcast transmission and reception in
the United States in 1953. The NTSC standards have not changed significantly
since their inception, except for the addition of new parameters for color
signals. An NTSC TV image has 525 horizontal lines per frame (complete
screen image). These lines are scanned from left to right, and from top to
bottom. Every other line is skipped. Thus it takes two screen scans to
complete a frame, one scan for the odd-numbered horizontal lines, and
another scan for the even-numbered lines. Each half-frame screen scan takes
approximately 1/60 of a second, so a complete frame is scanned every 1/30
second. This alternate-line scanning system is known as interlacing.
PAL is short for Phase Alternating Line and is the dominant television
standard in Europe. Whereas NTSC delivers 525 lines of resolution at 60
half-frames per second, PAL delivers 625 lines at 50 half-frames per second.
The two standards are incompatible, but this was not done to prohibit us
from copying videotapes or DVD's from different parts of the world -- they
simply didn't exist when the standards were developed. (It is comparable to
the 120-volt electrical standard used in the U.S. and the 220-volt standard
used almost everywhere else.)
It isn't necessary to keep buying machine after machine to play a myriad of
different standards. Equipment is available that will play both PAL and NTSC
standards and, though somewhat expensive, such a machine would allow you to
view probably 99% of all commercially available recordings from anywhere in
the world. As far as I know there is only one other standard used anywhere,
and that is PAL-M which is used in Brazil. I know little about it, but it
seems to be an animal all its own, although I understand that a PAL-M
machine will allow one to view both PAL-M and NTSC (but maybe not the other
way around?). Perhaps some of our South American listers could enlighten us
on the situation there.
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