[mythtv] [mythtv-commits] Ticket #2060: US cable frequency tables incorrect
Michael T. Dean
mtdean at thirdcontact.com
Fri Jul 21 19:29:53 UTC 2006
On 07/21/2006 02:06 PM, Daniel Kristjansson wrote:
>The variability in published tables on this is absolutely maddening.
>The FCC offsets you explained probably explains some of it and the
>bttv 62.5kHz limitation explains some of it (at least in the software
>I've looked at), but the rest of the variability seems unexplainable..
Yeah. As far as the "specifications" go, the FCC "Numerical designation
of television channels" (47CFR73.603) is available (for free) at
and gives the channel number for each frequency band. All our
ntsc_bcast frequencies are 1.25MHz higher than the lower boundary of the
band, so I'd say we can write them off as correct.
Myth's ntsc_bcast table, however, gives frequencies for channels 70-83,
but the FCC list doesn't because that frequency range (806-960MHz) was
reallocated for mobile radio services in 1970 under 35FR11179 (I
couldn't find it online, but the reallocation is referenced in
http://www.fcc.gov/omd/history/radio/documents/short_history.pdf ). It
probably doesn't hurt to leave them in there, but let me know if you
want to clean them out.
For cable (standard, HRC, and IRC), the EIA/CEA-542-A "Cable Television
Channel Identification Plan," has been in use for US cable TV since
1997, and is available from
. If you'd like, I can buy a copy (it's only $30--not one of those
$10,000 ones :). I tried to see (using a Google search) if any of the
"usual suspects" (ivtv, V4L, etc. projects) mentioned having a copy, but
didn't see anything.
I would guess that the DVB guys working on ATSC have it since they
actually use "EIA-542" in their frequency table filenames... So, if you
have some contacts there, you might be able to get them to verify our
list or guarantee theirs or...
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