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

Bruce Markey bjm at lvcm.com
Sun May 6 20:17:44 UTC 2007

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

>> likely that it will be recorded on 7-1 as 1071.

But it is deterministic and predictable. See:

> For the benefit of the OP, can we go a step farther and say that Myth
>  requires that any channels with different programming content must
> have unique callsigns?

No, absolutely not. This is one of the pillars of confusion
between channels (frequencies) and stations (buildings).

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. The
confusion is fueled in cases where a grabber grabs the listings
for more than one source from the same web page. In that case the
listings happen to be identical but that does not have to be true
and in many cases, it is not.

mysql> select sourceid,chanid,channum,callsign,xmltvid from channel where callsign='KVBC';
| sourceid | chanid | channum | callsign | xmltvid |
|        1 |   1003 | 3       | KVBC     | 10790   |
|        2 |   2123 | 123     | KVBC     | 21661   |

Here I have my local NBC affiliate available from analog and
digital cable. Both show programming originating from near the
corner of Las Vegas Blvd. and Foremaster. I can record "The
Apprentice" from either of two s-video inputs from STBs or any
of four coax cables connected to tuner inputs. However, on Sunday
afternoon, "Ebert & Roper" is shown on coax but the STBs show
"Nevada Newsmakers" on ch 123 (and during the first half of Leno
on weeknights). While I can record "Deal or No Deal" broadcast
from Foremaster from the channels for either source, I can only
record "Ebert & Roper" from channel 3 on Sunday afternoons.

Leading up to the 'new' scheduler in 0.15.x, there were several
examples of stations that are carried part time, local programming
in early evening/primetime, infomercials over night, and so on.

For a more extreme example, let's take CNN from Atlanta GA. On
My Cox cable channel 20 in Las Vegas, NV I see "Anderson Cooper
360" an 7pm PDT. At the same moment, someone in Ohio is watching
AC360 on 53 CNN at 10pm EDT. The schedule for CNN from Atlanta
does me no good. What I need to know is what Cox cable in LV
will be showing on its channel 20.

TV listings are per channel.

> The OP does not have his system set up that
> way ("I've been unable to browse listings for channels with duplicate
>  callsigns, even though they have different programming.").

This may be correct or a misunderstanding. If these two channels
carry programming primarily from the same station but have some
differences in their individual schedulers then I'd suggest
keeping the callsigns the same and using a different cosmetic
channum so the two channels (frequencies from a source) can be

For example, my local channel 6 may have some interference,
however, it appears that for the STB, this channel is sent as
digital data for the STB to convert back to NTSC. The picture
is much clearer so I prefer recording from source 2. But the
channel number is still in the analog range where as the digital
cable KVBC is given a number of 123. Therefore, I've changed the
channum for 2006 to "106" to show me that this is the digital
cable version. This isn't really 106 and the tuning info in 
"freqid" is still set to "6" but I did this in order to show me
the distinction between analog KVCW and digital KVCW so I can
tell which source was chosen for recording.

mysql> select sourceid,chanid,channum,freqid,callsign,xmltvid from channel where callsign='KVCW';
| sourceid | chanid | channum | freqid | callsign | xmltvid |
|        1 |   1006 | 6       | 6      | KVCW     | 10456   |
|        2 |   2006 | 106     | 6      | KVCW     | 10456   |

--  bjm

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