[opendtv] Re: BBC Demonstrates HDTV Broadcasts over SD Channels
- From: Mark Schubin <tvmark@xxxxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Thu, 23 Jun 2005 13:08:52 -0400
John Willkie wrote:
>Actually, you seem to be responding to something that nobody else said.
>Nobody -- at least this time around (me having learned a few years back) --
>said that pixels had to be square.
>
>
Neither did I. I referred to square-pixel SPACING. When you wrote
about dividing 480 by nine and multiplying by 16, whether you are aware
of it or not, you were invoking square-pixel spacing.
>could you address the ATSC compression format constraints? Are they
>optional?
>
The FCC did not adopt them, so, yes, they are entirely optional for
broadcasters. Unfortunately, some receivers won't work properly if
they're not used.
>Are they irrelevant?
>
They should be, but see the comment about receivers above. I am
permitted to comment on the testing ATTC performed on behalf of ATSC
T3/S6, because it was publicly available on the ATTC web site. They
tested seven receivers in a number of possible modes involving
720-active-sample lines. Five receivers had no problems. One had a
problem with one mode. A different one had a problem with a different mode.
TTFN,
Mark
>
>
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