On 11/10/06, Manfredi, Albert E <albert.e.manfredi@xxxxxxxxxx> wrote:
Craig Birkmaier wrote: >> Let's compare. You can transmit 4.5 Mb/s over normal 8-VSB >> with 15 dB of C/N margin, and send along HDTV or a couple >> or three of SDTV channels to boot, not just one NTSC. > > Really? Can you provide the parameters to do this? By my > calculations, you would use the entire 6 MHz channel to send > 4.5 Mbps of robust data - and that would leave ZERO room for > SDTV or HDTV. Of course I can. Okay, to play it safe, a Moviebeam service on plain old 8-VSB might only give people permission to join if they can measure, say, 17 to 20 dB of margin at a minimum. That is probably more comparable to the 40 dB they are now requiring for NSTC Dotcast. And, of course, this service can afford to contract LG or Samsung for "proper" 5th gen boxes. The good ones.
Funny I spent a year trying to find a way to buy "the good ones" from LG or any other vendor but was unsuccessful. Tell me how you do this trick please.
Done. Craig. That gives you 19.39 - 4.5 = 14.89 Mb/s left over for HDTV or multicast SDTV, or even one HDTV and one SDTV channel. > In the example used in the paper I referenced, the high > quality 8-VSB payload is reduced by ~4.5 Mbps to accommodate > SRS and ONE 1.5 Mbps robust channel. The most robust A-VSB service layers a 1/4 rate turbo code over the existing 2/3 rate Viterbi, which means that a *very* robust 1.5 Mb/s still leaves: 19.39 - (1.5 * 4) = 13.39 Mb/s of normal 8-VSB, for a few SD multicasts. Or, in a pinch, even 720 at 24p HDTV. This would apply to a Moviebeam service that wanted access to subscribers way outside of any HDTV reception range. So a completely different scenario from the limited Dotcast situation. > You get on a slippery slope real quick trying to compare > these standards. Not really. The only real difference is that COFDM figured out all these alternate modes ahead of time, while 8-VSB is doing it after the fact. But after all is said and done, both would end up being flexible in similar ways. To someone who just crawled out of a cave after 25 years, they will just look like two different ways of doing pretty much the same things. Bert
A robust 1.5 Mbps that may be available in a few years coupled with a still lousy 8-VSB 13.39 Mbps does not compare favorably with anything COFDM and I think a cave man would be able to tell the difference. Haven't you seen the commercials? Give those guys a break. Compare COFDM to A-VSB over the full 6 MHz channel. Bob Miller ---------------------------------------------------------------------- You can UNSUBSCRIBE from the OpenDTV list in two ways:- Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org
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