In-line... Bob Miller wrote:
At the moment broadcasters are contemplating going with a mobile variant of 8-VSB that could use most of the 6 MHz channel and I would think they would use MPEG4. While technically and legally OK it is not in the spirit of maintaining compatibility with legacy receivers. That spirit which was used to derail allowing a COFDM based modulation 8 years ago when there were very few legacy receivers to cry about. If it was true then it is far more true today.Could use is a far cry from will use or even should use. A meteor could strike you dead at any moment. Will that happen too?
If broadcasters actually get to the point of using something like AVSB with most of their 6 MHz channel I think they may be the first to say this is crazy and suggest starting over.
...your point here being?...
At that point there will be few early adopters still using OTA 8-VSB since they only can get one SD channel on it and they will have all migrated to cable or satellite. We will be down to the non voting poor demographic lot relying on OTA, maybe ONE% or so, who no one thought about in this transition so far anyway. With out the vocal early adopters and with possible a new and large mobile TV voting population with good demographics who are happy with mobile offering from others, it might be easy for broadcasters to suggest a switch in modulation and codec....it might be equally compelling for Broadcasters to offer Mobile services to this large universe of Mobile viewers so as to ensure they continue to watch them instead of others...and if they are then watching them and not others, why would you then want them to change to yet another modulation/codec solution?
/Wait till I get my hands wrapped around them...(which them you might ask...)/
And maybe well before 2012. Maybe in 2010.
...and maybe never.../Is the sky falling or is that just another meteor? Watch out! /:-)
Bob MillerOn Nov 28, 2007 11:00 AM, Manfredi, Albert E <albert.e.manfredi@xxxxxxxxxx <mailto:albert.e.manfredi@xxxxxxxxxx>> wrote:Tom Barry wrote: > Are we now assuming ATSC STB's or TV's will work indoors in urban > canyons? I didn't know that was really proven yet with off the > shelf equipment. We know there is nothing in physics that prevents this. We know that it's doable now in more or less easy fashion, most likely depending on the quality of the tuner (i.e. independent of the specific modulation scheme), using current state of the art demod. 8T-VSB today, in its basic wide mode, is about as far from the Shannon limit as DVB-T2 wants to be. But 8T-VSB even today is not there as reliably as DVB-T is in its current form is. Echo tolerance, and in particular leading echo tolerance, is not as good as that of COFDM at the same spectral efficiency setting. So it's a mixed bag, but one that continued development of receivers, without having to change the transmission standard, can address. Not a bad place to be, really. Eventually, perhaps, 8T-VSB may get to the point where the 2/3 fixed convolutional FEC becomes a limiting factor. That's where receivers are good enough that we could move to maybe 3/4 FEC, and get better than 3.3 b/s/Hz of spectral efficiency reliably. That would require a change to the transmission standard, so it's as difficult to do as DVB-T2 is. We're not there yet with 8T-VSB, but it could happen. For now, concentrating on receivers makes sense. Bert ---------------------------------------------------------------------- You can UNSUBSCRIBE from the OpenDTV list in two ways: - Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org - By sending a message to: opendtv-request@xxxxxxxxxxxxx <mailto:opendtv-request@xxxxxxxxxxxxx> with the word unsubscribe in the subject line.
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