[mythtv] [mythtv-commits] Ticket #3418: [13136] prevents seeing channels with duplicate callsigns

Daniel Kristjansson danielk at cuymedia.net
Sun May 6 23:50:57 UTC 2007

On Sun, 2007-05-06 at 13:17 -0700, Bruce Markey wrote:
> Michael T. Dean wrote:
> > On 05/06/2007 02:01 PM, MythTV wrote:
> >> #3418: [13136] prevents seeing channels with duplicate callsigns
> >> 
> >> 
> >> Comment(by danielk):
> >> 
> >> Just for the record, the program guide groups channels with the
> >> same callsign iff they have the same channel number. Take for
> >> example WABC-DT, it is listed as 7-1 from OTA and 1071 from CATV.
> >> The reason the channel is listed under both channel number in the
> >> program guide is only so that if you remember that the channel
> >> number is 1071 or 7-1 you will find it where you expect it in the
> >> ordered list. As far as MythTV is concerned they are the same
> >> channel, if you set up a manual recording on 1071 it is just as 
> s/channel/station/ # from the same building on different wires

Oops, I used the colloquial 'channel', I meant 'station'.

I'm not sure "from the same building on different wires" helps
people understand the difference though. In my region the local
PBS station runs 9 'stations', each with different callsigns:
  WNET    13.0 (13 VHF analog)
  WNET-HD 13.1 (61 UHF digital)
  WNET-SD 13.2 (61 UHF digital)
  WNET-13 13.3 (61 UHF digital)
  WLIW    21.0 (21 UHF analog)
  WLIW-HD 21.1 (22 UHF digital)
  WLIW-SD 21.2 (22 UHF digital)
  WLIW-3  21.3 (22 UHF digital)
  WLIW-4  21.4 (22 UHF digital)

I forget what 3 & 4 on WLIW are, I believe they are two children's
programming streams. Anyway, these are all programmed
by the same people in the same building but have completely
different schedules and different programming as well. These
are all available on different channels depending on how you
get them, OTA, cable or satellite. Each channel for each
'station' is identical, no matter how you get it because
WNET/WLIW is a "must carry". (FYI Both those HD stations
are craptastic, 1080i with enough bitrate to carry 480i).

The same is the case for the News Corporation, it has
4 'stations' in NYC with different callsigns:
 WNYW     5.0 (5  VHF analog)
 WNYW DT  5.1 (44 UHF digital) and 9.2 (38 UHF digital)
 WWOR     9.0 (9  VHF analog)
 WWOR DT  9.1 (38 UHF digital) and 5.2 (44 UHF digital)

In this case channel 5.1 and channel 9.2 are both the 'station'
"WNYW DT", and channel 9.1 and channel 5.2 are both the
'station' "WWOR DT". These are all programmed out of the same
building but each callsign corresponds to a different set of
programming, though in this case the analog stations are mostly
just low-def versions of the digital stations. These stations
are _not_ "must carry" stations so if you tune into them using
cable channel there may well be a different set of ads. Also
you can see in this example that even OTA, frequency != channel
and frequency != callsign, this is of course even more true
when you start mixing OTA with cable or satellite sources.

> >> likely that it will be recorded on 7-1 as 1071.
> But it is deterministic and predictable. See:
> http://www.mythtv.org/docs/mythtv-HOWTO-12.html#ss12.6

> People often want to jump to the conclusion that if two channels
> primarily carry programming from the same station, it therefore
> follows that the listings are identical. This is not true.
<snip, case of different programming on same callsign>

Hmm, if this is the case then there are two bugs we need to fix.
First, mythweb should use the same grouping as the program guide
(channum, callsign). Second, manual recordings should be based
on the channel not the station (currently if you create a manual
recording selecting "1071, WABC-HD" and MythTV has a "7-1
WABC-HD" you can end up with the wrong one being recorded.
(I ran into this with a couple FTA DVB-S channels, one without
listings, the other day.)

I also have to change those smarts I just added in the multirec
branch to check that the current programs are identical before
substituting one WABC for the other WABC when the desired one
of them is on an unavailable tuner and they have a different
channum, I thought that 'callsign' == 'programming stream
aside from commercials' in MythTV.

-- Daniel

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