[opendtv] Re: (CORRECTION) Backward Compatibility of Robust DTV Transmissions

  • From: John Willkie <johnwillkie@xxxxxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Tue, 7 Nov 2006 12:11:16 -0800 (GMT-08:00)

I don't think the issue here is to improve reception by legacy receivers, but 
to make sure that A-VSB doesn't break them.

And, in that light, I need to CORRECT something I posted yesterday about the 
mechanism that I thought would be used to transmit (at least some of) the 
training sequence.

I was clued into this a few months back by a Samsung consultant who told me of 
the idea of using "adaptation fields in every packet" including PSIP packets.  
I pushed back on that point, mentioning that PSI/PSIP only takes up a wee bit 
of the bandwidth.  I even asked a few simple questions.

I never heard back.

I had an email in my inbox yesterday that officially clued me in to the new 
approach to the adaptation fields.  I consciously avoided reading it before 
replying on this thread, so I wouldn't even be tempted to violate an NDA.

Now, I've read that official message.  All I can say is that my nit-picking of 
the approach as not being "backwards compatible" IS NO LONGER VALID; it has 
been overtaken by positive events.  I have carefully parsed this section of 
this message.  I can offer nothing in the way of details, until I learn it from 
a public source.


John Willkie

-----Original Message-----
>From: John Shutt <shuttj@xxxxxxxxx>
>Sent: Nov 7, 2006 8:37 AM
>To: opendtv@xxxxxxxxxxxxx
>Subject: [opendtv] Re: Backward Compatibility of Robust DTV Transmissions
>
>Al,
>
>Once a receiver is built, how much can be done ex post facto to improve the 
>performance?  With so many receivers designed around "blind equalization" 
>exclusively, I don't understand what sort of "training wheels" can be added 
>to ATSC to help them.
>
>I can see how one could create pseudo-training sequences ala A-VSB that 
>could help new receivers improve their performance without upsetting 
>existing hardware, but I think the best one can hope for with legacy 
>receivers is similar to the Hippocratic oath, "first do no harm."
>
>John
>
>----- Original Message ----- 
>From: "Allen Le Roy Limberg" <allimberg@xxxxxxxxxxxx>
>To: <opendtv@xxxxxxxxxxxxx>
>Sent: Tuesday, November 07, 2006 8:25 AM
>Subject: [opendtv] Backward Compatibility of Robust DTV Transmissions
>
>
>> Actually, backward compatibility has been given short shrift in proposals
>> for robust 8VSB.  These proposals time division multiplex robust
>> transmissions with ordinary 8VSB, but no portion of the robust 
>> transmission
>> is usefully received by legacy receivers.  In short, training wheels
>> approaches have been ignored.
>
>
> 
> 
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