[opendtv] Re: Sixty-three TV stations to launch mobile DTV service this year
- From: "John Shutt" <shuttj@xxxxxxxxx>
- To: "OpenDTV" <opendtv@xxxxxxxxxxxxx>
- Date: Thu, 15 Jan 2009 17:20:24 -0500
John,
Please see embedded replies:
----- Original Message -----
From: "John Willkie" <johnwillkie@xxxxxxxxxxxxx>
Indeed, I think that stuff -- to the extent I understand it -- is quite
elegant.
Absolutely. I agree. M/H seems to be very well thought out and elegant in
it's minimal disruption of existing data structures.
I'd be interested in you pointing me to reserved fields in A/53:2007 and
A/65c that you believe now will be unreserved as a result of CS/153 being
adopted.
I did state "Data Field Sync." I have by no means done an exhaustive
examination of A/153, but while trying to get through the document I found
this:
"5.3.2.13.1 Data Field Sync
The diagram of the Data Field Sync in A/53 Part 2:2007 is repeated here for
convenience of the reader as the reserved area is redefined in the
immediately
following sections (see Figure 5.32)."
The item that caught my eye was the phrase "the reserved area is redefined
in the immediately following sections".
This would appear to be in conflict with A/53:2007 which states:
"6.5.2.4 Reserved
"In the 8-VSB mode, 92 symbols of the last 104 symbols shall be reserved,
and they shall be followed by the 12 symbols defined below. To maintain a
longer period with a flat spectrum, it is recommended that these 92 symbols
be filled with a continuation of the PN63 sequence when only 8-VSB is
present.
"When one or more enhanced data transmission methods are used, the
previously reserved symbols (including the 12 precode symbols used for 8-VSB
and E8-VSB) shall be numbered from 1 to 104, in the order transmitted. The
12 precode symbols shall be preceded by 10 symbols that shall be used to
signal the presence of an enhancement or enhancements, as defined below.
The use of some or all of the remaining 82 symbols shall be defined by each
enhancement."
There may be 'wiggle room' in A/53:2007 to allow a different loading of
those reserved Data Field Sync bytes. Again, I don't know.
As far as A/65C goes, a closer examination has revealed that I was mistaken
about any reserved PSIP fields being used. I misunderstood the explanation
of handling legacy PSIP compatibly during my first cursory reading of the
candidate standard, so I apologize. As I understand it, a separate M/H
'service guide' is included in the M/H data stream.
And there is still the E8-VSB use of null packet PIDs to hide their
enhanced payload data from legacy receivers. Not that there is a single
E8-VSB receiver available to the consumer, but M/H does appear to use a
different data scheme after the null packet PID that is different than that
defined in A/53:2007.
I am just trying to understand what the FCC might interpret as allowable
under their adopted rules vs. what clearly is a well thought out M/H scheme
that is compatible with legacy receivers.
It wouldn't take much for the FCC to adopt A/153 by reference, and indeed to
adopt the latest version of A/53 at the same time. I believe at one point
there was inquiry made by the FCC for comments to have them automatically
adopt any ATSC standards as FCC rules. I don't think that went anywhere.
John
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