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RE: History of 29.9



> -----Original Message-----
> From:	David L. Tosh [SMTP:dlt at earthlink.net]
> Sent:	Friday, February 13, 1998 6:00 PM
> To:	multiple recipients of
> Subject:	Re: History of 29.9
> 
> At 03:31 PM 2/13/98 -0500, Craig Fearing wrote:
> >The NTSC subcarrier frequency is precisely 3579545 Hz, 
> 
> Close enough...
> 
For what it is worth, the US frame rate issue is supposed to be "healed"
some time after the year 2006 when the analog NTSC stations start shutting
down and people pop over to 60.00 Hz.  But then we have another problem.
Nobody has done adequate testing of the ATSC television system at 60.00 Hz.
Nobody will have done adequate testing of the CEMA receiver base at 60.00
Hz.  (There isn't even any production equipment at the ATTC to test it
with.)  Most of the sets will probably lock to the new vertical frequency.
But some may not.  It is only a little bit off.  But you never know.  Due to
the sensitivity of these new and fragile designs some receiver manufacturers
are telling me that they'll include a number of crystals in their VCXO just
to be sure.  This, of course, drives up the cost.  So we all pay for the
brain damage of those ancient NTSC decisions once again.

This also reminds me of a story I heard yesterday:  If you look only at the
electricity bill of a typical analog NTSC station you'll find it's a big
number.  (Many many kilobucks per month to drive the transmitter.)  As
stations and markets convert over to DTV there will be a time where the old
viewer base gets down toward the 10-20% number, where it will probably
linger for a long time, maybe well after 2006.  (That is, 10-20% have NOT
bought a new DTV set and rely on the older analog NTSC service.)  There will
be a big incentive for the TV station to drive that number toward zero or at
least under 5% so they can legally shut off that service if only to save the
power bill.    Depending on the market, one possibility is for them to buy
set top boxes and give them away to their viewer base.  Cheaper than keeping
NTSC going in the long run.  But then by definition those STB's will still
be driving older analog NTSC television sets, many of which will lose their
mind if you try to drive their NTSC inputs at 60.00 Hz.  The STB's can
receive the new DTV service at 60.00 Hz but I seriously doubt if they will
perform a framerate conversion between 59.94 and 60.00 in a $300 box.  So
what they are going to do is drop frames.  Those viewers will simply have to
tolerate the artifacts.  They pay for the old decisions yet again.

Eight of the formats in the ATSC's emission format specification, Table 3,
are 704 pixels per scan line as opposed to 720 pixels per scan line like the
SMPTE and ITU production specs say they should be.  In other words 704
pixels by 480 lines instead of 720 pixels by 480 lines.  Not a big number
but unless that gets changed now we'll have to live with that (just like
59.94) for at least half a century to come and probably more.  The 480 line
formats are going to be where the bulk of DTV programming happens.

The ATSC spec for 50Hz countries is the full 720 pixels.  Most other nations
and broadcast standards have adopted 720 pixels.  There is zero technical
reason to stick with 704 in the US.  Bizarre.  Here we go again.

Similarly, the ATSC has a specification for its AC-3 audio bitrate that is
lower than what consumers will be buying on DVDs and other sources.  Again,
it is not a big difference but why not fix it now instead of letting it
linger?  Why should the new DTV terrestrial service have an inferior quality
level to any other form of digital entertainment? 






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