Listen, lets get real. If any broadcaster was to seriously consider using A-VSB what would they do with it? Lets say they use it to simulcast their regular programming in a robust mode so it is receivable for almost everyone. Are they going to adhere to MPEG2 in this 1.5 Mbps robust channel? I doubt it. I think we break company with compatibility right there. Yes A-VSB is backward compatible in theory but not in practice. We can have our cake and eat it now. We can preach compatibility while going incompatible. If I were a broadcaster and resigned to live with 8-VSB and A-VSB I would go full A-VSB with one SD MPEG2 program using minimal bits and use the rest with MPEG4 all at 1/2. How does that come out? Up to one Mbps up front cost. 18.39/2 = 9.20 Mbps or more of which you need 3 Mbps for the required SD MPEG2 and you have 6.20 Mbps or more left for a robust MPEG4. You can do a robust 720P with that right? Good for the speed limit maybe. Maybe you could really crimp that MPEG2 by going with a B&W weather and traffic map updated once an hour. Then you might get 8 Mbps or more for the MPEG4 side. Of course this would not be in the spirit of staying the course with legacy receivers. How long after the death of OTA do these legacy receivers still control the discussion? It would seem that we should be doing our utmost to stop the injection of more of these legacy receivers into the OTA bloodstream instead of offering a subsidy for doing so. Bob Miller On 11/10/06, Bob Miller <robmxa@xxxxxxxxx> wrote:
On 11/10/06, Manfredi, Albert E <albert.e.manfredi@xxxxxxxxxx> wrote: > John Shutt wrote: > > > Bob had 5th gen LG boxes, using the same LG block that is in the > > DirecTV boxes. Bob's problem was that those "5th generation" > > chips didn't work nearly as well as the prototype "Cold Fusion" > > 5th generation box that got both Mark Schubin and Sinclair so > > darned excited two years ago. > > I know he tried some no-name clones with the 5th gen LG chip, and that > those clones didn't do "as well as" the prototype. But that doesn't mean > they are crap, either. We have all surmised the reason to be that they > weren't using the better tuner designs. > > AND > > The 5th gen LG-based USB receivers for PCs have been reviewed by the > trade press on several occasions, and they all do very well. I keep > repeating, over and over, that reception of TV stations from 80 Km using > only a (single) indoor antenna, reliably, from these LG 5th gen-based > designs is nothing to sneeze at. > > AND > > The 5th gen LG do not measure as well as the Samsung Gemini in certain > very key areas. > > AND > > The training techniques used in 5th gen sets can also be improved upon, > at least as far as I know, even without changing anything in the bit > stream. > > Put all of this together and it is ridiculous to think that the only way > to get acceptable DTT here is to use only A-VSB. That's just the sort of > annoying rhetoric certain politicians seem to crave. I try to ignore it > and not respond to it. I try. > > A-VSB is instead comparable to either HM or to 16-QAM modes in COFDM. > > For example, tuning the spectral efficiency down gradually to increase > robustness, using the SRS mode of A-VSB, is very similar to increasing > FEC in COFDM, and even backing down to 16-QAM. Same gradual improvement > in robustness. > > Yes, A-VSB can be used. No, it is not mandatory. And if you are after > spectral efficiency, you want to minimize use of A-VSB. > > Bert > > Minimal use of both 8-VSB and A-VSB is recommended and most likely. Bob Miller
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