[mythtv-users] Issues with using an IR blaster

Michael T. Dean mtdean at thirdcontact.com
Wed Aug 2 00:53:18 UTC 2006

On 08/01/2006 01:00 PM, Cool Frood wrote:

>I've run against a couple of issues using the IR blaster with a
>PVR-150 card. I'm running MythTV version 0.19.
>1.  The external channel changer command gets the frequency id instead
>of the channel number when it is asked to change the channel.  I
>looked into the sources and I could verify this and also rectify this.
> Perhaps this is fixed in one of the bugfix releases.

It definitely hasn't been fixed in any bugfixes (in 0.19-fixes or SVN 
trunk) because that's the desired behavior.  The freqid is the 
identifier used for a channel's frequency (which could be either a 
frequency in kHz /or/ a channel number); whereas, the channel number is 
the /user-specified/ number the user enters to tell Myth to change to 
another channel.  In other words, users can (and do) change channel 
numbers to anything they want instead of getting stuck with the cable 
companies idiotic^H^H^H^H^H^H^H"good-for-us-but-not-for-users" numbering 
scheme (i.e. putting Fox 35 on channel 3--users can, instead, change Fox 
35 to be on channel 35).

When using an external channel change script that requires channel 
number, you /must/ specify the channel number in the freqid field 
instead of a frequency in kHz.  (Note, also, that in the case I referred 
to above, that would mean channel 3--the channel number used by the 
external cable box--instead of channel 35.)  You may edit the values in 
the freqid field inside the mythtv-setup channel editor.

>2. There is a setting to tune the TV-capture tuner to a particular
>channel (in my case, channel 3) when using an external channel
>changer.  The problem is that channel 3 is not in my database of

The video source should provide a list of all channels that are 
available through that video source.  If your cable box is set up to 
output an RF-modulated signal on channel 3 (or channel 4), you specify a 
value for:

Preset tuner to channel
Leave this blank unless you have an external tuner that is connected to 
the tuner input of your card. If so, you will need to specify the preset 
channel for the signal (normally 3 or 4).

If you're having issues with this option, see 
http://www.gossamer-threads.com/lists/mythtv/users/209677#209677 and 

> even though it is part of the data received from zap2it.  My
>question is, how do I fix the channel data received from zap2it.

Huh?  How can it be not be there, but be there?  What do you need to fix?

>Secondly, why should MythTV go looking for channel 3 in the database
>anyway if you have an external channel changer?

It won't unless you tell MythTV to change to channel 3--at which point, 
if it's not a valid channel, Myth tells you that it doesn't exist (how 
could Myth change to a channel that doesn't exist).

Just in case this helps...  If you're using an RF-modulated output from 
your cable box on channel 3, you specify that in the "Preset tuner to 
channel" setting, then you tell Myth to change to the channel you want 
to watch (i.e. 217).  Myth then sets the capture card to channel 3 and 
sends the freqid (which should be 217) to the external channel change 
script.  The external channel change script then tells the 
cable/satellite box to change to channel 217.  And, it's quite possible 
that the video source may not have a channel 3--if the cable company 
doesn't use that channel number--which is fine because you're watching 
channel 217, not channel 3 (only the capture card is tuned to channel 3 
and only because you're using RF-modulated output on channel 3 from the 
cable/satellite box).

(However, as mentioned above, the "Preset tuner to channel" setting may 
not work now, so you may want to add an appropriate line to your channel 
change script to change the capture card to the appropriate channel.)


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