[mythtv] HDTV doc diff for channel settings

Brandon Beattie brandon+myth at linuxis.us
Wed Jul 21 11:15:49 EDT 2004

The lowest I have seen is 29.  I did some quick math, UHF frequency for
14-69 channels is 470-806 Mhz.  This is about 6.1Mhz per channel.  If
you take 14 channels worth below 470 it's about 395, which is still
higher than channels 7-13 VHF (174-216 Mhz) and channels 2-6 (54-88
Mhz).  But below 470 is used for other /critical/ technologies.  
225-400Mhz is used for ATC/military communication, landing
systems, and other general aviation transmissions.  400-406 is for US
Goverment usages (Undefined).  420-450 is for Ham radio.  And 450-470 is
used for military, fire, "local" goverment, and "businesses".  If you
are getting channels 13, or below, the broadcaster is sending over radio
frequencies that are for other purposes, which may be fine, I can't find
any information detailing regulations on 395-470 for what would be HDTV
channels 1-14.  

For the second item, that may be true.  The station tech I spoke with
just said he came from the east coast and everyone out there basically
said you should only use program ID 1 for the main HD channel and if you
are only doing standard def the acceptable thing was to use program id 2
instead, and reserve 1 for when they go HD.  All my stations out here
also follow what he said with the exception of 1 that's using program ID
1 for standard def, and 3 that don't have anything on program ID 1 and
are broadcasting in standard def on program id 2.  The sad thing is it
appears that there is no standard that everyone will probably agree on
and follow.  Using id 1 for station information sounds really good, but
I don't see anyone out here following that.  The one station that
appears to have program information is running it on 34-7 here.


On Tue, Jul 20, 2004 at 10:28:28PM -0400, Daniel Thor Kristjansson wrote:
> This is a great improvement. But a couple nitpicks...
> * The frequency part of the "freqid" can be any channel starting at 2,
>   in my city there are a couple ATSC stations on channel 12.
> * It is recommended to the broadcasters that they don't change the
>   program id's often and that they never use program id 1. This is for
>   faster tuning, and for compatability with DVB which uses program id 1
>   for the Network Information Table. If you are using a freqid such as
>   "44-1" and it works, this is only because MythTV tries to guess at the
>   program id if you got it wrong, and often guesses correctly.
> -- Daniel
> On Tue, 20 Jul 2004, Brandon Beattie wrote:
> ]2 additions.
> ]
> ]I added one paragraph regarding what CPU is recommended for systems with
> ]multiple HDTV tuners.  I've had so many problems with watching HDTV when
> ]myth is trying to commercial detect more than one or two shows at a
> ]time (Commercial detect set to low CPU).  A 2.4Ghz box may work just
> ]fine for viewing live HDTV or previously recorded, but if you drop even
> ]2 HDTV tuners and have more than 1 or 2 shows to commercial flag a 2.4Ghz
> ]system is not going to cut it.
> ]
> ]The other addition is regarding how to setup myth for subchannels with
> ]HDTV.  Examples, links to dtvstream, and explanation on how things work.
> ]
> ]I did change the sgml file, but I didn't add anything more than <sectx>
> ]tags, someone who knows sgml may want to beautify my technical jabber.
> ]
> ]--Brandon
> ]

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