[opendtv] Re: News: H.P. to Report an Advance in Adaptable Circuitry
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 17 Jan 2007 06:50:56 -0500
At 9:56 AM -0800 1/16/07, John Willkie wrote:
What makes you think we don't? Ever hear of A/97 -- as just an example?
Have you ever heard of E-VSB, E-AC-3, and perhaps A-VSB?
These are not extensible. They do not work with legacy ATSC receivers.
To be fair, one could argue for two different definitions of extensibility:
1. Enhancing a standard in a manner that adds functionality without
breaking existing receivers.
2. Enhancing a standard in a manner that adds functionality to
existing receivers.
Your examples are all of the first type.
We routinely add new capabilities to computers and web appliances via
software upgrades, which are examples of the second type. And in some
cases products are designed to accept hardware upgrades as well.
We argued for BOTH of the second examples during the Advanced
Television process. It is not that difficult to develop products that
can be upgraded after they have been shipped, although it can
increase the cost. But there are huge costs in terms of what you
cannot do if everything is locked down.
Just ask Mark Schubin about adding a legal MPEG-2 format to the ATSC
standard - "Sorry, but we cannot add 720 x 480 because it might break
some existing receivers."
And here's an even better example. We tried to amend the MPEG-2
standard to use a "Reserved Extension" to add a flag to help identify
breaks in the 3:2 pulldown frame sequence for 23.97/24P film source.
The MPEG-2 standard was designed to be extensible as described in #1
above. You should be able to use reserved extensions in new gear,
while older products that do not understand the reserved extension
simply ignore the bits in this field. But some of the early MPEG-2
decoders simply "hard wired" some of the reserved extensions. That
is, they always expect that extension to be off "0." But if the bit
is used "1," the old product would break.
As a result, the MPEG-2 standard cannot be extended without breaking
some older products. We were blocked from using the reserved
extension by the Japanese delegation because it would break some
products that they did not design properly. In effect, not the MPEG-2
standard cannot be extended.
Regards
Craig
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