[opendtv] Re: China writes its own digital TV standard
- From: "Albert Manfredi" <bert22306@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sat, 01 Jul 2006 17:00:20 -0400
Bob Miller wrote:
>I will not and have not argued that DVB-T receivers are
>compatible with DVB-H because they are not at least by
>my definition of compatible. It is disengeneous, IMO, to
>argue that since DVB-H, E-VSB or A-VSB don't "break"
>legacy receivers they are compatible.
Well, then, be consistent. If you're going to persist in railing against
A-VSB and E-VSB as upgrades to ATSC in general, then you should rail against
DVB-H as an upgrade to DVB, in general.
Upgrades of the transmission standard do not often work with legacy
receivers. Strereo FM did not work with legacy receivers either. But the
fact that it didn't break mono FM receivers is what made it a winner.
(Perhaps you didn't know this, but stereo FM degrades FM for mono receivers,
because it reduces the max audio frequency from stratospheric levels of mono
FM, which were in theory upwards of 70 KHz, to "merely" 15 KHz.)
>If you were to dedicate all 6 MHz to E-VSB or A-VSB all current receivers
>would not receive anything anymore than if you were using COFDM.
And if you dedicate 6 MHz to DVB-H? Would any other receivers than DVB-H be
able to use that signal?
>It is amazing how twisted logic can be when you want to get
>around the obvious. E-VSB and A-VSB are not fixes for 8-VSB
>they are new modulations that are incompatible with all current
>receivers.
That's nonsense. John Shutt often mentioned the issue of a transmitter going
down in power for maintenance. That's a perfect case for E-VSB. The low
power alternate transmitter can continue to transmit an SD version of the
signal, as plain 8-VSB, and simultaneously a more robust, perhaps sub-SD
quality signal that covers its entire market area. So in fact, you have
added value to the ATSC standard.
[The new Chinese DTT standard]
>They are not backward compatible. They are new modulations. They
>don't work with any legacy COFDM or 8-VSB receivers. They didn't
>change COFDM they are using their own TDS-OFDM.
So they have changed COFDM from the one used by DVB-T. Let's not twist
logic. Much like A-VSB does to 8-VSB, they have added training sequences to
COFDM that were not previously there.
>So the plan now is to take a 6 MHz station and limit the SD
>MPEG2 content to 3 Mbps, deliver as much content as possible
>with A-VSB in the remaining bandwidth using MPEG4 AVC.
It sounds like someone's proposed transition scheme. Depending on the
specifics of A-VSB, it might even be attractive. I don't know enough to say.
You're the one whose stuck on COFDM as being the non plus ultra. Not me. If
enough smart people keep trying, I've no doubt they can come up with
something better.
Bert
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