[mythtv-users] Twin Cities MythTV Users - Channel 23.1

[Tim Schall]

OK, I haven't used MythTV in a long time and know nothing about using it for 
digital.  Being the transmission and encoding engineer for the PBS station 
out here in Seattle what I do know something about is how an MPEG/ATSC 
stream is put together.

Understand that PSIP and MPEG program PID's don't really have anything to do 
with each other.  What seems to be messed up here is the Program Allocation 
Table (PAT).  Some tuners use it.  Some don't.  It's transmission is 
required and it's required to be correct.

The PAT at its simplest form tells the receiver where to find the programs. 
Sorta like this:
    I know about 2 programs.
        Program #3 is a 704x480 SD 4:3 show with two AC3 audio streams at 
192kbps each.
            PCR (Program Clock Reference) can be recovered from PID 0x30
            Video can be recovered from PID 0x31
            Audio #1 can be recovered from PID 0x34
            Audio #2 can be recovered from PID 0x35
            etc....

It could go one for a long time.  Mind does because I have 3SD programs and 
1HD program stat mux'd into one bit stream.

At any rate, like I say, some receivers use the PAT some take other measures 
to build their own.  Either way, if it ain't right bad things tend to 
happen.

It sure sounds like Myth us getting confused by a bad PAT.  That would cause 
the receiver hardware to lock onto the signal just fine (Explaing the 96% 
part) and whine about the bit stream (Explaining the No Picture part.).

If you have access to a recent windows machine (Put down the rotten 
eggs....) go find a copy of a program called TSReader and see if it shows 
anything wrong with that transport stream.  Don't waste your time calling 
the station.  You'll most likely get a hold of an idiot viewer services rep 
(If you can find a human at all.) that has no idea what you're talking 
about.

----- Original Message ----- 
From: "Mathias Gibbens" <mathias.gibbens at gmail.com>
To: "Discussion about mythtv" <mythtv-users at mythtv.org>
Sent: Sunday, February 17, 2008 2:58 PM
Subject: Re: [mythtv-users] Twin Cities MythTV Users - Channel 23.1


I'm also unable to watch channel 23.1 (HD) and 23.2 (SD) OTA using my
HDHR. Signal strength is 96%, but MythTV can't establish a signal
lock. No other channels are having problems. My log is filled with the
following message:

2008-02-17 16:49:33.841 Program #1 not found in PAT!
Program Association Table
 PSIP tableID(0x0) length(17) extension(0x637)
      version(1) current(1) section(0) last_section(0)
         tsid: 1591
 programCount: 2
  program number 3 has PID 0x  30   data  0x0 0x3 0x224 0x48
  program number 4 has PID 0x  40   data  0x0 0x4 0x224 0x64

Running MythTV 0.20.20070821-1 on Fedora 8 x86_64.

HTH,
Mathias

On Feb 17, 2008 12:16 PM, Mercury Morris <mercury.morris at gmail.com> wrote:
> Watching or recording one specific channel (WUCW - 23.1) is no longer 
> possible
> with any of my three MythTV systems.  Something changed during the week of
> 9-16 February, but I haven't been able to diagnose the problem, exactly.
>
> I use a roof-top antenna (OTA) to receive the signals from all of the
> TV stations
> in the Twin Cities.  Only this one channel has a problem - all the
> others continue
> working OK.
>
> After searching the archives, I deleted all the channels and did a
> complete re-scan
> using the Channel Editor in mythtv-setup.  The results were as
> expected (some new
> subchannels were detected) and a mythfilldatabase completed
> successfully.  Still,
> after the re-scan, I can't record channel 23.1.  The backend log is
> filled with messages:
>
>     "Program #1 not found in PAT!"
>
> Do you have a MythTV system that uses an antenna to receive and record
> Channel 23.1
> from the Twin Cities?  If so, can you still record Channel 23.1?
>
> My MythTV systems are running mythbackend version: 0.21.20070820-1 and 
> have been
> completely stable and error-free for six months.
>
> Any help or additional information would be greatly appreciated.
>
> Thanks.
>
> --
> MM
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> mythtv-users at mythtv.org
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