[opendtv] Re: Integrated DTV PSIP
- From: cbenham@xxxxxxxxxxx
- To: opendtv@xxxxxxxxxxxxx
- Date: Tue, 06 Dec 2005 20:34:30 +0000
How do you KNOW the receivers were tested in exactly the same way with the
exact same test equipment under exactly the same conditions?
YOU DON'T!!!!!!!
> Cliff Benham wrote:
>
> > After 40 plus years in broadcast engineering I can
> > assure you it is impossible to judge the performance of
> > *anything* by it's spec sheet or sales brochure.
>
> Hmmm.
>
> Since all I have done is quote directly out of CRC test
> results, and you quoted my post, am I to conclude that
> the Communications Research Centre of Canada in fact
> only writes sales brochures?
>
> > Direct comparison under identical test conditions is the
> > *only* way to know which device works best.
>
> Not wanting to sound overly pedantic here, but ...
>
> When an engineer designs something, he has to use both
> measurements and real-world tests. The measurements are
> needed to associate behavior in the real world with
> specific aspects of the design. It is only with these
> measurements, and associated real-world tests, that an
> engineer can go back and tweak the design in a attempt
> to affect real-world behavior. Otherwise, he's just
> shooting in the dark.
>
> The example of the comparative results of the newer
> receivers in Mark Schubin's apartment are a good case in
> point. The one which was most successful was one that did
> not measure best in equalizer performance, with respect
> to both static or dynamic echo. This leads to the
> conclusion, at least in *that* site, that equalizer
> performance was adequate "as is" with the LG, and that it
> must have been other aspects of the design which made it
> particularly successful.
>
> This conclusion was further supported by the results with
> the LG clones, which used the same equalizer as the LG
> prototype and yet got results more similar to those of
> the other, less successful contestants. Good, not great.
>
> Furthermore:
>
> The LG did not test as well as A/74 guidelines. Therefore,
> one can conclude that A/74 guidelines with respect to
> echo tolerance *per se* are probably more than adequate,
> but that A/74 guidelines *may* not adequately address other
> aspects of receiver design. And that these other aspects
> have an important impact on real world performance.
>
> This was the gist of the post you quoted. Sales brochures
> have never been the issue in any of this, at least not
> from my posts.
>
> Bert
>
>
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