[opendtv] Re: Well, well, well; five years to match 1999 COFDM indoor antenna performance

Craig Birkmaier wrote:

> Obviously the Europeans felt that they could deliver significantly
> improved image quality by using their current scanning rates while
> delivering digital component video instead of analog composite
> video. And they could do this in a way that is fully compatible
> with the existing analog receiver base (with an affordable set-top
> box).

Honestly, I think the Euro decision to stick with SDTV was not based
on much more than the dismal failure of HD-MAC. However, IMO, the
failure of HD-MAC and MUSE had more to do with the fact that they
were HD-only solutions, separate from regular old TV, than with
any idea that regular old TV resolution was "good enough."

A properly integrated HDTV system, where the same infrastructure
is used by all TVs and each TV extracts from the signal the most
image quality it can use, seems to be a very viable solution.

> I do not know whether the 100Hz sets can accept a 576P input;
> that is a matter for the digital image processing circuitry in
> the set. But the added cost to support 576P is trivial, once you
> increase the scanning rate.

And the result is a very nice EDTV picture, especially if the
source info was transmitted at 576p rather than 576i. But this
is not the same as HDTV. It looks like a nice, crisp TV image,
but you can't see individual threads in the clothing of the
actors.

By the way, this subject line of this thread is false. As the
Canadian CRC article in IEEE Transactions on Broadacsting,
September 2003 states:

"As shown in Fig. 4, the DVB-T receiver could handle pre and
post ghosts over a wider range. It had a window of 74us working
within a delay range of -74 to +74 us, and capable of resolving
zero dB ghost for a signal having a high C/N of 31 dB, and less
than 1 dB ghost for a signal with a C/N of 22 dB."

So what is the true comparison?

What the CRC is descibing, a single 0 dB ghost, is approximately
equal to Brazil C and D. Whereas Brazil E has two 0 dB ghosts,
along with the 0 dB main signal.

The CRC test shows the COFDM receiver successful as long as the
signal margin is 31 dB (at 19.7 Mb/s in 6 MHz). And yet, both
the Linx and the LG units can now decode the more difficult
Brazil E at 25 dB margin (with reacquisition of signal), which
is considerably better than those COFDM results in the easier
echo environments.

However, with a GI of 1/16, the COFDM receiver has -74 to +74
us echo tolerance, compared with -38 to +38 us for the Linx and
-50 to +50 us for the LG. So the Linx unit is almost identical
to COFDM with a GI of 1/32. The LG is between 1/32 and 1/16
equivalent.

So in fact, performance of these new ATSC receivers is quite
bit improved over those early COFDM receivers, at least as far
as decoding signals with loud echoes, at 3.3 b/s/Hz.

Bert
 
 
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