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DTV Standard

E

e-dawg

With the US have transitioned to digital on June 12th 2009. I notice that the world has 4 different DTV standards ATSC for north America, DVB-T for Europe and Asia, and ISDB for Japan, Brazil, and Peru, and DMB-T for China only. Why do we have 4 different DTV standards instead of 1?
Also, how can different DTV standards be compatible?
 
They are not compatible.

And, off the top of my head, I think there are more like, EIGHT different standards. ATSC was planned (by it's creators) to be a standard for the western hemisphere, but didn't make it. I read where Sony even talked Brazil in to going with a customized-version of their ISDB-T system, hoping to swing the whole South American continent that way, by promising to build a huge IC factory there, but never came through.

It's all politics.

There are even variations of the standard formats, too. See this link for more, and IIRC, there is a spreadsheet in there that gives all the details, by country: http://www.dvb.org/about_dvb/dvb_worldwide/index.xml
 
I'm sure some outfit will come up with a single low cost mass-produced piece of silicon that can decode all the DVB variants along with ISDB, DMB-T, and ATSC.

Mr. English is correct, a lot of it is politics. Though it's a shame we're stuck with ATSC here in America, because the DVB-T and the new DVB-T2 standard appears to have much more flexibility for broadcasters than does ATSC... though I understand why we have ATSC, just that DVB-T would do better in places like Chicago or NYC... but ATSC would perform better in the plain states.

Mark.
 
All of the standards have their own pluses and minuses.

As I recall, the COFDM-based standards, as used in Europe within an 8 MHz channel, were not believed to have enough bandwidth for U.S. 6-MHz channels. This would have pecluded HDTV and many of the sub-channels.
And, there were some differences in coverage. We were told, by our (many) consultants, that a COFDM-based system might require a distributed-transmission system in most larger markets, with stations having to purchase expensive property to build numerous transmission sites.

Probably the biggest differences between the standards is, their age. Every new standard has some improvements over the last one.
 
I've heard bad things about both ATSC and DVB-T. I've heard few bad things about ISDB-T.

- Trip
 
Also remember that the standard was basically decided in the mid to late 90s. And then it was developed. By 2000 ATSC looked great for longer distances but it was clear that the shorter urban areas might have trouble.

I recall reading and it was basically shoved off as "Yeah but we can overcome that alter on." Which they might.

CODFM is better for urban areas that are dense. This is why it was chosen in Europe and Australia. (Australia's population is concentraded in the six capital cities which are dense.

The OTA system also suffered 'cause many wrote it off saying 85% of TV households use cable which has another system all together.

ATSC and CODFM has been debated at length an if you read you'll find both systems have strong points and weak points, depending on location, terrain and signal splitting.

But we all know how fast computing techonology moves. ATSC and CODFM are already obsolete by technical standards, meaning better improvements could be put in place, but it's costly to keep replacing systems.

I've read ATSC will last from anywhere from 2025 to 2050, where they will probably scrap it and start over again.
 
kenglish said:
All of the standards have their own pluses and minuses.

As I recall, the COFDM-based standards, as used in Europe within an 8 MHz channel, were not believed to have enough bandwidth for U.S. 6-MHz channels. This would have pecluded HDTV and many of the sub-channels.
And, there were some differences in coverage. We were told, by our (many) consultants, that a COFDM-based system might require a distributed-transmission system in most larger markets, with stations having to purchase expensive property to build numerous transmission sites.

Probably the biggest differences between the standards is, their age. Every new standard has some improvements over the last one.
Click to expand...

What I'd heard was that COFDM modulation has a VERY high peak-to-average power ratio. It's not particularly difficult to achieve at relatively low powers but pretty hard to accomplish at high power. Probably not a big deal in Europe where stations were already used to using multiple lower-powered transmitters but a dealbreaker in the U.S. where a TV license only conveys authority for one site.

(well, until DTV Replacement Translators came along...)

Personally I thought Sinclair had the right idea when they asked for rules to allow each station to choose whether to use 8VSB or COFDM.
 
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