OK, I'll try a Basic English summary, but I haven't written BASIC statements for awhile:
Numerous on-the-air tests have identified a fairly large number of specific locations that
had "sufficient' signal strength, but could not be decoded by 2nd or 3rd Generation STB's.
Both the 5th Gen Zenith/LG and the LINX Prototypes have been retested using a set of
"captured" RF test signals from these earlier tests (some are included in ATSC A/74).
There have also been some on-air tests that were repeated at the same locations that
caused problems in earlier tests. Both the Zenith/LG and LINX Prototype demonstrated
improvements by dramatically reducing the number of "problematic" locations. They also
are first STBs claiming to decode all of the captured Brazil test ensembles A-E.
The lab and on-air tests by Brazil and Australia compared the performance of several
different receiver systems, including ATSC, DBV-T and ISDB-T . See my 19July05 post:http://hdtv.forsandiego.com/messages...html#POST19348
So some of the new ATSC Decoder IC's provide an important and dramatic improvement.
The difficult part is determining which is "better" when looking at the latest chips from
Zenith/LG, Micronas/LINX, ATI/NxtWave, Broadcom, Zoran/Oren, ST Microelectronics, et. al.
Adding to the confusion is lack of information on what was actually in the prototypes
and trying to associate Zenith/LG's generational jargon with IC and STB part numbers.
There has been a lot of hype about Zenith/LG's so-called 5th Gen ATSC Decoder IC.
Mark Shubin and Bill Miller have done a lot of tests in New York and and thus far
ONLY the Zenith/LG PROTOTYPE with the 5th Gen LGDT3303 IC truly succeeded in
Schubin's particular location where the multipath is extremely severe. An LG LCD
HDTV with the LGDT3303 chip was a close second. STB's with ATI NXT2004 didn't succeed.
Unfortunately, the DVICO FusionHDTV5 Gold PCI card, a new Prototype PCI card
from BTTI and another MIT STB Prototype with the LGDT3303 IC's did not operate
as well as the Zenith/LG Prototype. Right now there is some speculation as to WHY.
Could be the RF Front End in the Prototype was somehow "better". It is likely that
the prototype had different firmware than the production LGDT3303's. They also might
have had different firmware when tested by Schubin than that tested by the CRC lab.
The 5th Gen LG (as well as LINX, ATI Theater and Broadcom BCM3517/3520 ICs)
all claim big improvements in being able to handle a large pre-echo delay.
These large pre- and post-echo performance improvements may or may not be
important in Schubin's location. [Manufacturers need to display the equalizer settings!!!]
On-air test data has shown that for many locations the multipath consists of a single
strong signal plus several other delayed signals (multipath) that are at lower signal
strengths (typically 5-15+ dB lower). Even the 2nd and 3rd Generation STBs should
receive most of these signals, since the pre- and post-echo delays are "typically" well
within the A/74 Guidelines of -10 to +40us. The issue of extremely long equalizer delay
times is concerned with handling those rare cases when the (highly reflective) object
causing the reflection (presumably a skyscraper) is quite far away (50 us is a delta of
over 9 miles). For big city locations, this can be important. For most of us in the 'burbs,
it's probably not a concern.
The CRC lab test results above show that the Zenith/LG prototype had difficulties with
the so-called "0 dB Echo" test condition. For some other locations, especially urban and/or
indoor locations, there may not be a single strong signal because the direct path might be
blocked. For the worst case "0 dB Echo" case, all of the multipath signals have roughly the
same signal strength. The Micronas/LINX handled the "0 dB Echo" tests much better.
ATI/NxtWave has claimed that their NXT200x series, as well as Theater 310/313 series
of ICs can also handle this condition, but I have not seen any confirmation tests.
Which brings us back to REALITY....sort of...
Mark Schubin and Bob Miller continue to invite manufacturers to subject their equipment to
a "real world" urban canyon environment where indoor antennas are the norm.
A Samsung test is currently underway....should learn more next few weeks....
The new MIT STB with 5th Gen LGDT3303 has not yet hit the streets.
I would like to see a test of other products, such as Broadcom and ATI Theater.
Micronas/LINX just announced long anticipated ATSC Decoder IC, maybe STB by early 2006?
I encourage people to see WHAT'S IN YOUR STB so we know what tuner/chip is in which product.
I continue to search for meaningful laboratory and on-air test reports for the current
generation of ATSC equipment so we can try to separate the hype and try to separate
the wheat from the chaff. Unfortunately, most lab tests are either on prototypes that
may or may not represent performance for a production unit, or are conducted by an
independent agency which cannot name names. Such as would probably be the case
if Brazil decides to conduct a update of their earlier ATSC vs DVB-T vs ISDB-T tests.
OK, let me close with a BASIC IF-THEN statement:
IF meaningful production test results, THEN can compare.