Re: BAd News!
- From: phil-news-nospam@xxxxxxxx
- Date: 1 Nov 2005 16:58:24 GMT
On Sun, 30 Oct 2005 20:31:39 GMT Bob Miller <robmx@xxxxxxxxxxxxx> wrote:
| phil-news-nospam@xxxxxxxx wrote:
|> On Sun, 30 Oct 2005 06:20:49 GMT Bob Miller <robmx@xxxxxxxxxxxxx> wrote:
|>
|> | It is just bad enough to guarantee failure. Doesn't have to be that way.
|> | Other countries do not have this problem. They are using versions of
|> | COFDM and countries going digital now will also be using MPEG4.
|>
|> ATSC does appear to be headed towards MPEG4.
|>
| The only way that a broadcaster can use MPEG4 with ATSC is to OBSOLETE
| all current receivers sold since 1998. That was one of the main reasons
| given for not allowing COFDM that all receivers sold before 2000 would
| be made obsolete, all 2000 of them.
This all depends on whether the broadcasters have a choice on a case
by case basis. I had suggested around here a while back that maybe we
could give broadcasters a choice of 8-VSB vs. COFDM on a case by case
basis (e.g. one broadcaster could switch even between programs). That
might have been bad to make such choices so much, but I bet that if they
do decide to go with MPEG4, it will be in a way that allows broadcasters
to choose on a program by program basis ... e.g. it won't be mandated,
just allowed (but they might mandate support in new TVs).
| The reality is that when the US decided to change the codec for the
| "required" free to air SD or HD program they might as well change the
| modulation as well as the MAIN argument for not changing is that
| receivers will be made obsolete and changing the codec does just that.
You have not yet convinced me that COFDM will be better for the majority
of households using OTA TV in the USA.
| If you change then it would be insane not to take advantage of the
| improvements in modulation that have occurred since 1997. Even 8-VSB
| could be upgraded.
If the modulation were changed, I'd go with a form of QAM that uses a
group coded constellation confined in a circular parameter over a
triangular lattice. For example a circle with a radius of the square
root of 73 confines 265 points, sufficient for a group coding of 256.
| All modulations should be considered at that time.
Only if there is a cause for modulation change. I believe a change to
MPEG4 would be much less costly than a change to COFDM. MPEG4 might
well be a software upgrade.
| SO saying that ATSC is heading for MPEG4 is insane. Any change would
| open the door to the retesting of ALL known modulations including DVB-T,
| ISDB-T and DMB-T from China.
Not really. It would just be a new compression available for the same
transport format.
|> | That means that countries like China, Malaysia, Borneo, Mongolia, the
|> | Ivory Coast and Russia will have far better OTA DTV than the US.
|>
|> Actually not. Their OTA TV will be principly limited to urban areas
|> and the areas served by repeaters and translators.
|>
| So you have the inside track on the long term DTV future of all these
| countries? They will never deploy a substantial DTV coverage?
|
| And what if they don't for what ever reason possibly economic? They
| still chose COFDM.
I think you didn't understand what I said. For the kind of coverage done
in the USA with one big transmitter, it's normal for many other countries
to deploy multitudes of smaller transmitters.
|>
|> | The worst RF environment in the world, New York City has reception like
|> | this mobile with COFDM and a single 100 Watt transmitter. This in a city
|> | with MEGA (that is a MILLION) WATT DTV stations on the Empire State
|> | Building that you can't receive 8 blocks away.
|>
|> Can't get analog their, either.
|>
| That has nothing to do with it but is also untrue in the most part. Mark
| Schubin could/can receive all analog stations in his apartment watchable
| with a simple antenna on the top of his TV. This was not and is not true
| of 8-VSB even today. The only instance in which he could match NTSC
| analog with 8-VSB was with an LG prototype a year ago just before LG
| quit building any 8-VSB receivers.
Just how good was this analog picture in the first place?
Based on what I have read in a few places so far, there are plenty of
people with snowy analog pictures that became crystal clear with ATSC
and 8-VSB on the same antenna. That's rather good considering the power
reduction in DTV.
| Obviously I can't show you that because COFDM is not allowed in the US.
| It would be as good or better than 8-VSB as the Australian test, the
| Sinclair test in Baltimore and the MSTV test showed when Sinclair
| retested the seven sites where COFDM had failed and where 8-VSB had
| worked at six sites.
I would not have any qualms about running a test of COFDM vs. 8-VSB on
one of the ham bands (just running test patterns and other non-commercial
stuff for content). 1 watt of power or less can easily reach 500 km or
more from a weather balloon at 30 km high. We could try 8-VSB, 16-VSB,
64-QAM, 256-QAM, COFDM, and for a base reference, analog VSB. Let's
cut the power to 10 milliwatts just for grins.
| Upon retest with a proper receiver, COFDM worked in ALL seven sites
| including the one site where 8-VSB had failed.
| The opposite of watching in Scranton what you could receive in New York
| is not obvious at all. Lots of variables. Being able to watch DTV over
| the radio horizon is not necessarily a good thing. The over powered US
| analog broadcast system causes interference that is unnecessary if
| multipath was under control.
I think to propose COFDM you must also propose a complete change in
the structure of how TV is transmitted here. That can means a whole
lot of expense in many markets with very small populations to support
it. That really won't fly unless the government builds it (and that
isn't going to happen in the USA).
| Having the digital broadcast system duplicate that flawed over powered
| and outdated system is wrong. By lowering power and using on channel
| repeaters you could better sculpt a stations coverage and you could
| modernize our system and allow the reuse of a lot of spectrum that now
| goes to waste.
Who is going to pay for this system?
| Not true I am one of the few who actively tested and test the latest
| 8-VSB receivers. I do so in the hope that we will find one we can use.
| My ears are open unlike those of Congress, the FCC and most
| broadcasters. Any of them doing any testing of receivers except Sinclair?
The nature of OTA TV (big sticks, big power, wide reach) isn't going
to change here, especially considering we have found a modulation that
actually works with it.
|> | It is our spectrum, yours and mine and it could be receivable mobile and
|> | portable on simple inexpensive receivers and simple omni antennas. It
|> | could deliver TWICE the programming to us free and clear with MPEG4.
|>
|> The needs for fixed reception and mobile reception work differently.
|> Trying to find one method that service both will be a compromise that
|> ends up serving neither very well.
|>
| The only difference is that being able to receive mobile is only a
| testament to the robustness of the signal. NOTHING else. If you can
| receive mobile you also have the best system for fixed reception.
No. It is a test of one aspect of robustness in favor of not having
another aspect of robustness that you seem to not be interested in.
| I would love for you to explain a situation where a modulation that
| works mobile would not work as well as another modulation when a fixed
| site is tested. This should be good.
COFDM has a lower average-to-peak signal strength than 8-VSB. That needs
to be higher to have a greater information density in a give power spectrum.
| I had a standing offer to test COFDM against 8-VSB where I said that
| using the same power and broadcast antenna with both COFDM and 8-VSB I
| would let the 8-VSB folks pick any site where they could receive 8-VSB
| and I would drive around that site receiving COFDM mobile.
Same average power, or same peak power?
Presumably in locations on the order of 125 miles from the transmitter,
where analog requires a big antenna on a tall mast, DTV can be expected
to have a similar requirement. If a smaller antenna works in DTV, then
there's more power than needed. Bring the power level down (which is
being done with DTV as compared to analog) to where the same antenna
works for the vast majority, then you have it about right. Do this for
both 8-VSB and COFDM. Which will have the lowest power level?
| There is no PERIOD in Washington. Broadcasters have been denied
| multicast must carry twice and still they fight on. Multicast must carry
| will only die after Congress gives it to broadcasters and then the cable
| guys take it to the Supreme Court. Then ALL must carry will die.
Remember what cable TV used to be long ago. It was supposed to be a
means for those who didn't want the big antenna on the tall stick (in
some places, tall enough to look over a mountain) to be able to get
TV reception at all. Must carry came along to prevent cable serving
this purpose from playing games with the broadcasters.
I'll favor an exception to must carry on the basis of "all or nothing".
That is a cable system can elect to _not_ be a "OTA provider" by not
carrying any OTA at all. But if they choose to be an "OTA provider",
then I think it is only right that they do it completely.
Their argument that they don't have the bandwidth is a bunch of BS.
They have the bandwidth and they know damned well they have the bandwidth.
They just want to take the bandwidth for their own profiteering.
| The digital transition will be over when the last analog transmitter is
| turned off not before. The rumor mill already says that both 2009 dates
| are fictitious. That as the date set approaches broadcasters will go to
| the public with a new set of delay tactics chief among which will be the
| lack of receiver standards.
There are new and growing voices to speed up the transition and grab
the spectrum for public service and auctioning off. I'm sure some will
have some delay tactics pulled, but overall it appears to be headed to
happening.
| Congress will jump like a frog to get out of that boiling pot.
| Broadcasters will not bring the temp up slowly. They will as one feign
| indignation that receivers standards are not set or met.
What standards are you talking about? Your perpetual quest to change
it all to COFDM so you can watch TV while driving?
| You will see services that compete directly with 8-VSB on channels above
| 51 and they will work better using COFDM than 8-VSB does for both fixed
| and mobile.
These services will be using a completely different structure for their
transmitters ... lots of smaller ones. That will indeed be interesting,
but I will also just wait and see how well they cover rural areas like
the entire states of West Virginia or Kansas.
| Also simply not true and NTSC was both portable, mobile and fixed. It
| did not work well at any of them but that is no reason to give up mobile
| and portable. That is another issue that broadcasters will feign
| surprise at at the last moment.
NTSC has always been more lousy at mobile that at fixed. A portable TV
in downtown Wheeling WV gets all 3 locals on analog very lousy. And you
can see the antenna towers from the right places. People do not expect
it to work, so they have solved it one way or another, such as using cable,
or a good directional antenna, or listen to the radio instead. DTV is
not trying to cover these cases where analog didn't work well. Maybe it
should have. But they weren't trying to change the whole model of TV.
Perhaps if the likes of Qualcomm prove that a good deployment can really
work, have 100% coverage, and be cheaper, maybe the next big transition
in the future will be to that style of transmission. Then COFDM can shine.
But that isn't the direction the regular stations are doing today.
| "Where is mobile reception? My God we can't let this transition happen.
| We were promised mobile reception by the 8-VSB crowd way back in 2001."
| broadcasters will say. "They said they would have it within six months.
| That 8-VSB will work mobile as well as COFDM. That was after they said
| they had it in 1999."
I never heard such a promise. The promise I heard was better pictures,
both in the form of cleaner pictures and higher definition capability.
| Broadcasters will also say "Won't have it in 2009 either. And the
| broadcasters can use that tool at the last minute too. Hey US public the
| government wants to take your analog away and do a digital that doesn't
| work fixed, mobile or portable. they haven't set receiver standards and
| they have ignored the fact that the rest of the world has a working DTV
| system that works mobile and portable and fixed."
It works fixed. Channel differences change the dynamics somewhat, but
I've read where the FCC is granting power changes to some stations when
they discover their DTV signal isn't getting to at least 99% of their
previous analog coverage. Obviously, stations moving from VHF to UHF
(as so many are doing) will have issues like this, especially in the
fringe areas (UHF doesn't bend as easily).
| They are good at this. They are broadcasters and they can tell the story
| well when it suits them.
| Expect it about November of 2008. A major campaign. And after the delay
| we will have switched to or allowed COFDM of some sort with a deadline
| of 2012. By which time, because it will be in their interest, all
| broadcasters will have switched to COFDM and will welcome the end of analog.
All the very same cries about "they want to break your analog TV" will
then be applied as "they want to break the digital TV you just bought"
with regard to the switch to COFDM, if anyone ever gets serious with it.
How many 8-VSB TVs and STBs that don't also include COFDM have been sold
now?
--
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| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
| (first name) at ipal.net | http://phil.ipal.org/ http://ka9wgn.ham.org/ |
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