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

Bruce Markey bjm at lvcm.com
Mon May 7 20:59:53 UTC 2007

Daniel Kristjansson wrote:
> 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)

PBS is a network that feeds its affiliates. /WNET$/ and /WLIW$/
are station. 13.n and 21.n are all channels. "PBS" proper
is not fed to homes directly but programming is sent via
satellite to their affiliates for broadcast over the air
or on a channel from a service.

Back to CNN. This is a network that is sent to affiliates.
In my area, Cox cable is essentially the affiliate that is
broadcasting the CNN feed over channel 20 and CNNHN on 22.
However, the local CBS affiliate prepares 5 minutes of local
news for CNNHN that is shown at :25 and :55. Even though these
are not shown in the listings as separate programming, the
"CNNHN" shown in Las Vegas is different than the CNNHN for PDT
in Los Angeles, Reno or Phoenix.

> 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

True, and therefore these have different callsigns though
the string of characters look similar and there may be other
similarities. However, a different broadcast license from the
FCC to broadcast other programming over a different assigned
frequency with a different station identification is a different
"station". I never said that one building can only broadcast
one station =). HBO may be even grey-er.

mysql> select sourceid,chanid,channum,freqid,callsign,xmltvid from channel where callsign like 'HBO%';
| sourceid | chanid | channum | freqid | callsign | xmltvid |
|        2 |   2200 | 200     | 200    | HBOP     | 10244   |
|        2 |   2202 | 202     | 202    | HBOSIGP  | 16576   |
|        2 |   2203 | 203     | 203    | HBOFP    | 16619   |
|        2 |   2204 | 204     | 204    | HBOCP    | 18430   |
|        2 |   2205 | 205     | 205    | HBOZP    | 18432   |
|        2 |   2210 | 210     | 210    | HBO      | 10240   |
|        2 |   2211 | 211     | 211    | HBO2     | 10241   |
|        2 |   2212 | 212     | 212    | HBOSIG   | 10243   |
|        2 |   2213 | 213     | 213    | HBOF     | 16585   |

I have nine HBO* channels. There are five different sequences
of programming. 200 HBO is the EDT broadcast and 210 HBOP is
the same sequence delayed by three hours. Again, the cable
provider is the affiliate broadcasting these feeds over cable
channels. I could, for example, set the callsigns to be the
same so that a kChannelRecord (note that this is mis-named =)
rule would match the 7pm showing on 200 and the 10pm showing
on 210 of the same program. In practice, I wouldn't do this
because I'd use FindOne for a movie on HBO which doesn't care
about chanid or callsign. If the same movie might also have
a censored version on basic cable, I might use the Custom Record
example "AND channel.callsign LIKE 'HBO%'". This would match
any of the nine HBOs but exclude all other showings.

> 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

I can't parse the phrase "Each channel for each 'station' is
identical". Each channel is a unique piece of information for
a receiving device to tune to a potential broadcast signal. A
station broadcasts content over assigned channels. However, I
infer that you intended to say something like 'the content from
the station is identical for every channel that carries the

> 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

I agree that frequency != callsign. I disagree that frequency !=
channel. A channel is the frequency (or ID) for a receiving
device to 'tune' to in order to receive a broadcast signal. The
origin of the programming that is broadcast over that frequency
(if any) is a different issue. Two or more channels may carry
programming from the same station and that programming may be
identical but they are still two (or more) different frequencies
which the receiving device may tune to. 9.0, 9 VHF analog, 9.1,
38 UHF digital, 5.2, and 44 UHF digital are six examples of
channels. If I tried tuning devices to these six channels in
southern Nevada, most would have snow or no signal and none
would show WWOR content but the receiving device could be
instructed to tune to that carrier frequency. Therefore, each
frequency is a channel (regardless of the content sent over
that channel).

My point is that we fall into the trap of saying that 'IFL
Battleground is on 9' and '9.0 is the exact same channel'.
Well, it is WWOR that broadcasts IFL and tuning an NTSC device
to channel 9 in New York should show the WWOR content. 9.0
would be entirely different tuning information for an HDTV
device to determine which packets to decode in order to see
the content sent from WWOR.

For myth, we need to know that if a New Yorker wants to watch
IFL, chanid 1009 could tell an NTSC tuner input associated with
video source 1 that it needs to send the V4L ioctl for freqid 9
or an HDTV card with an input for video source 2 should use the
2009 major 9 and minor 0 to set the card to download the WWOR

What she needs from zap2it is a list of what programs to expect
from freqid 9 when 1009 is used and a list of the programs that
will be shown when the HDTV card is set to 9.0. These may have
different DD stationids stored in channel.xmltvid (another mis-
leading name). The programids and times may be identical but
the HD channel may have the program.hdtv flag set for 2009
showings when the broadcast originates in HDTV. There may be
some other programs that are only shown on the HD channel but
I don't know if that is true in this case. I do know that it
is true in other cases. However, she will want to set the
channel.callsign to "WWOR" for myth's sake.

First, let's say that WWOR has generic episodes of "Family Feud"
at 3pm each day. If the callsigns for 1009 and 2009 are different,
myth must assume that generic episodes of "Family Feud" are almost
surely different specific episode from different stations so it
schedules 1009 at 3pm and 2009 at 3 to record two different Feuds.
By using the same callsign, it assumes that a generic 3 o'clock
Family Feud is the same specific episode from any of the channels
that carry WWOR and therefore only needs to record it from one

Second, she is only recording IFL to be able to converse with
her boyfriend. Dancing With the Stars must, of course, record
in HD on her only HD card and therefore it is okay for the Single
record rule for the IFL event to use 1009 on an NTSC card to
capture the same programid at the same start time from a WWOR

> 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
> Yep.
>> 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).

Yes. Long ago the EPG used to show every chanid. If two sources
had the same callsign and channum (cable 3 KVBC and digital STB
3 KVBC) the EPG would show duplicate rows for no apparent reason.
Filtering these to show one row is a cosmetic hack which has no
bearing on scheduling decisions. A question in this thread is
what if two channels (sigh, frequency identifiers) carry mostly
the same listings from the same station but with some differences
and the program.channum are the same, how can you be sure which
channel is shown in the EPG? Doctor, it hurts. Don't do that. A
suggestion was made that the callsigns should differ but that
will affect schedule decisions. I suggest that the callsigns
should remain the same but use a different cosmetic channel.channum
so the EPG will show two rows and as a visual aid everywhere to
clue you in on which channel (fre...) is being referenced.

> 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.)

This is a little fishy. Manual record rules can, do and should
behave like rules that match showing in the listings. If two
channels are given the same callsign, we should assume that the
content is predominately the same. If that is not true then change
the callsigns. Therefore the manual timeslot for either WABC-HD
channel should grab the same content. However, it is possible
in a rare exceptional case that the manual rule is for content
only shown on one of the channels and not the other but is not
shown in the listings. In that case, the preferred input can be
set in the rule's Scheduling Options to force which input should
be used. The ability for the majority of manual rules to failover
to another channel from the same station should not be sacrificed
for this rare exception.
> 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.

Right. This is part of the thought that I don't care what CNN
is broadcasting from Atlanta GA, what I need to know is what
Cox cable 20 will be showing from CNN. Regardless of if callsigns
are the same, different or similar, we need to know what specific
shows to expect when we tune to a specific channel(!). On Sunday
evenings, I've needed a program entry for 1003 (3 KVBC), 10pm,
"The Apprentice". Another row for 2123 (123 KVBC) that tells me
that sending 123 to the channel change script then recording from
s-video would also capture "The Apprentice" from this NBC affiliate.
However, a few hours earlier I could only record Ebert & Roper
from 1003 but I could have recorded Nevada Newsmakers on 123 at
the same time from an s-video input.

--  bjm

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