On 11/12/06, Manfredi, Albert E <albert.e.manfredi@xxxxxxxxxx> wrote:
Bob Miller wrote: > I didn't spell it out but all the conversations I have been > privey to suggest that broadcasters would be using MPEG4 > with any A-VSB robust mode which makes all current receivers > incompatible. Well, then that's a completely different discussion, isn't it. We were talking about the technical aspects of A-VSB, not how some particular broadcasters might want to use it.
Anything I am saying about compatibility is only addressed to the simple fact that if you are going to use the broadcast spectrum with any change to the modulation or codec so as to make current receivers obsolete you open the door to the discussion of changing everything. That is if you allow A-VSB which could be used on 90% of the spectrum and could be used with MPEG4/AVC you beg the question why don't we consider OTHER modulations and codecs as well. The reality is that if A-VSB is allowed that over some period of time market pressures will dictate that it be used as much as possible and with the most efficient codec. Over that period of time all current receivers will become 90% obsolete receiving only that which broadcasters are compelled to broadcast in MPEG2 with A-VSB or 8-VSB. So it is hypocritical to pretend that A-VSB is backward compatible when it will not IMO be used that way. Instead we should be saying, if we are honest, that A-VSB represents in reality a non compatible modulation that will be used with a non compatible codec. And if we say that then we should also say that all modulations and codecs should be on the table for comparison to A-VSB. The the false argument of protecting legacy receivers is just that, a false argument.
Clearly, as we've discussed for many years, there is nothing that makes 8-VSB incompatible with MPEG-4/AVC. These are only implementation issues, not technical ones. Anyone can make life difficult for TV viewers, no matter what modulation standard is used.
Who said that anything makes 8-VSB incompatible with MPEG-4? We are talking about incompatibility with current 8-VSB receivers. Only implementations issues? Implementing MPEG4 with current receivers would cost more than a brand new DVB-T receiver and we would still be stuck with 8-VSB. Not a bargain.
Here's the way I look at it. In the US, we can all enjoy HDTV today. In Europe, what HDTV there is OTA is incompatible with virtually all receivers in consumers' homes. By contrast, in Europe, the DTT stream can be adjusted for robustness compatibly, whereas in the US it cannot yet.
Very strange argument. What does Europe have to do with the US modulation? They made a choice for SD instead of HD. A choice. Here in the US we are talking about upgrading a miserable modulation with a patch that is incompatible with current receivers if used as it will be used.
So compatibility issues are by no means the sole province of ATSC. > If you have all of 1.5 Mbps who is going to use MPEG2 with > that? For Moviebeam? These are file transfers not meant to be consumed in real time. That is what we were talking about. Besides which, a Moviebeam service is perfectly capable of using AVC in its files, since they also provide the receiver box.
Any spectrum they use will not be receivable by any current receiver if they use A-VSB and MPEG-4. And to that extent they make all current receivers incompatible. If that is OK then lets make it OK to use any part of the spectrum with DVB-T COFDM. Same thing. Lets let 6 broadcasters all put their required SD MPEG2 on one common channel and use their full 6 MHz channels with DVB-T. In fact if we are being creative I can think of a hundred other ways to play this game. As soon as you let A-VSB be used with MPEG-4 you open the pandora's box. Why can't we use other modulations and codecs if we also supply our own receiver? Whether it is received in real time or like Moviebeam in non real time makes no difference. I want to use DVB-T COFDM and MPEG-4 with my own receivers and I will make sure that the consumer can still receive one SD channel for free in MPEG2 on legacy receivers for every channel I so use. Any problems with that?
I'm saying, that 1.5 Mb/s, using let's say A-VSB in 1/4 rate STS mode, does not in any way make the remaining 13 Mb/s less robust or incompatible with all existing receivers. And, of course, that is only the worst case example.
Again whoever ever said anything like this? Who are you arguing with? Bob Miller
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