BOC-L Digest / Still in the Shadows

[Eric Siegerman]

On Tue, Jun 01, 2004 at 11:43:17PM +0100, deadearnest wrote:
> analogue TV?????I am more in the dark than I thought - I may be displaying
> a lamentable grasp of technology here, but I didn;t think theTV had anything
> to do with it - after all I get analogue and digital on my TV -sorry, but a
> lot of this loses me!!!

You've got a set-top box for pulling in the digital, right?  It
probably generates a PAL (i.e. analogue) signal that your TV can
understand -- the same as (so I gather from what Paul says) a DVD
player does.

I say "probably" because I presume that they now make TV sets
that can take a digital signal directly, and you might in fact
have one of those.  In that case, I suppose the set-top box's
main function is to decrypt the signal to make sure you can't see
it unless you've paid for it.

But even if your TV accepts both, most peoples' don't (i.e. any
set more than a few years old), so their set-top boxes do the
D-to-A conversion.

Part of what makes this all so confusing is the ambiguous use of
terminology.  Strictly speaking, NTSC (I'll leave PAL well alone,
and so limit myself to stuff I'm only half-ignorant of :-) is a
standard for the analogue encoding of a television signal.  I
presume it includes all sorts of stuff about how the beginning of
a new scan line, or of a new vertical scan, is signalled (the
horizontal and vertical sync, resp.); how colour information is
piggybacked onto the B&W signal in such a way that B&W TVs can
ignore it; and a hundred other details.  Two of those many
details are that the signal to be encoded shall have 525 scan
lines and 60 vertical scans per second.

But people also use "NTSC" to refer to "video that's suitable for
encoding into an NTSC signal" i.e. which has 525 lines and 30
frames per second (60 divided by two -- don't ask, but if you
insist on asking, the short answer is "interlace") and perhaps a
few other requirements.  One might call such data "NTSC" even
when it's still digital, and so the rest of the NTSC standard
simply doesn't (yet) apply to it.  Somebody who knows this stuff
cold can understand immediately from context which meaning is
intended.  Anybody else just gets confused.

Similarly "DVD" is used to refer to either the media or the
player, as well as to the standard(s?) documents involved.  We
all do that -- "my new Hawkwind DVD" vs. "your new Panasonic
DVD".  But when the topic of discussion gets more technical, I
for one have to read between the lines to dope out which sense is
meant (and I might well guess wrong), and I'm sure a lot of
people are completely lost.

--

|  | /\
|-_|/  >   Eric Siegerman, Toronto, Ont.        erics at telepres.com
|  |  /
It must be said that they would have sounded better if the singer
wouldn't throw his fellow band members to the ground and toss the
drum kit around during songs.
        - Patrick Lenneau