[mythtv-users] Dual NTSC/ATSC Setup

John Sturgeon john at sturgeonfamily.com
Thu Jun 3 19:35:29 EDT 2004


Jarod Wilson wrote:

> On Jun 2, 2004, at 21:13, David A. Greene wrote:
>
>> What do I specify as an audio source?  Doesn't the MPEG already
>> contain the audio?
>
>
> You shouldn't have to spec anything for audio source, but if you have 
> issues, I seem to recall some of them being resolved by simply setting 
> the audio source to /dev/dsp (which in my case, is a symlink to 
> /dev/dsp0). The MPEG does indeed already contain the audio though.
>

Typically here, for the HDTV stuff, you are getting all of your audio 
through an AC3 stream.  Since this is the case, you need to decide 
whether you want to pass the audio stream through spdif to an amplifier, 
or if you want to decode it.  That will dictate which device you use.  
If you choose to pass-through the AC3 stream, then you should use ALSA.

>>>> Now of course I
>>>> don't know how to go about specifying an over-the-air HDTV
>>>> source as my video sources list doesn't seem to include
>>>> anything like that.
>>>
>>> You basically pull down the corresponding non-HDTV guide data, then 
>>> edit the frequency tables. At least that used to be what you had to 
>>> do, I haven't played with my pcHDTV card in ages...
>>
>>
>> Ok, by "edit the frequency" you mean freqid, right?
>
>
> Yes.

One weird thing is that the Zap2It DataDirect service does provide the 
digital channels (and sub channels) EPG data, yet it still does not put 
the correct frequency in the freqid field.  You must manually edit it, 
as Jarod says.

You can get the frequency from www.titantv.com.

>
>> What about subchannels?
>> The other PBS station has five of them (17.1-17.5 all under
>> HDTV channel 16 -- the NTSC channel is at 17).
>
>

First, you should use dtvscan  /dev/dtv to get the channels and sub 
channels available to you, that will give you the frequency.  In MythTV 
you need to use a combination of frequency and subchannel ID to work.  
In your example above, your PBS station would be 16-1, 16-2, 16-3, 16-4 
and 16-5.  If a station is not broadcasting subchannels, then you can 
just say '16' and it will default to channel one.

> Check out antennaweb.org, it should give you all the freqids you need, 
> I believe. I vaguely recall creating different channels for each of 
> the PBS sub-channels in my area, and then assigning one sub-channel to 
> each's freqid. Check out this, if you haven't already:
>
> http://www.pchdtv.com/forum/viewtopic.php?t=12
>
>
>> Right now whenever I press "y" in myth it locks up and
>> reports a 0% signal.  I set the HDTV video source to
>> start on channel 34 (the PBS HDTV station).  How do I
>> get the HDTV channels to show up in browse/scan mode?
>> They show up in the guide but not in the full-screen
>> live tv browse mode.  I also can't flip channels
>> down from 2 (the lowest) to get to 215 (the highest).
>> Is having a gap in channel numbers a bad thing?  Right
>> now the cable stops at 125 and HDTV starts at channum
>> 200.
>
>
> Hm... I *think* you want a channel with freqid 34 to get the PBS 
> station, but again, not sure...
>
>> With dtvsignal channel 34 looks very strong.  Some of
>> the others are at zero, but that's more a function of
>> my antenna.  I need to get a better one, apparently.  :(
>
>
> Yeah, I spent over $400 putting mine up, and have hardly had the time 
> to do anything with it...

A quick note here.  HDTV is *highly* directional.  If you are in the 
middle of a city, you might have sources coming at you from completely 
different angles.  The antennaweb.org site that Jarod mentioned lets you 
input your address, and it will recommend an antenna for you.  Simple 
UHF antennas are all that is required to receive an HDTV signal.  Heck, 
some people use coat hangers.  I got a sliver sensor antenna ($25.00) 
and mounted it in my attic and I get phenomenal reception for all of the 
major networks + PBS.  I had a cable guy install it for $75.00 (two 
story house... I wasn't about to do all that wiring myself).  He used a 
spectrum analyzer to point the antenna in the optimal direction.



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