[mythtv-users] External channel change command for Sky box

Nick Morrott knowledgejunkie at gmail.com
Tue Mar 20 20:16:25 UTC 2007

On 20/03/07, Graeme McClinton <graeme.mcclinton at gmail.com> wrote:
> Now, I have this working partially
>  I have a Sky box connected to the s-vid on a PVR-250, and I'm using a
> USB-UIRT to change the channel on the Sky box.
>  I'm using this
> http://www.mythtv.org/wiki/index.php/Script_-_SKY_channel_changer
>    script to change the channel.
>  When I start watching live tv it only works if the startchan in the db is
> set to a nonexistant channel. Which is fair enough I think, as mythtv is
> tuning nothing, the tuning is happening in the Sky box.
>  When I change channel, the USB-UIRT does its thing and successfully changes
> channel, and the new channel number is entered into the db. However, this is
> where live TV stops.
>  If I try to restart live TV, it hangs on a black screen for around a
> minute, then goes back to the myth home screen.
>  If I manually go into the database and change the startchan back to a
> nonexistant channel then restart the backend, it works again.
>  Here is what I think is relevant info line from my channels table, one of
> the sky channels
>  chanid 4304
>  channum 106
>  freqid 106
>  sourceid 4
>  callsign SKYON
>  name Sky One
>  I used this
> http://www.mythtv.org/wiki/index.php/Sky_frequency_numbers
>      to determine freqids and channums.
> It looks as if myth is getting confused when it sees a real channel from the
> db in the startchan, tries to tune it, but there is nothing to do
>  Where am I going wrong?

This sounds like a problem with your channel setup and/or channel
changer. For video sources with external channel changers, you need to
ensure all channels on that source have valid freqid settings, as this
is what is passed to the channel change script when you change
channels in LiveTV or start a recording.

In my experience (I use a channel change script with VirginMedia
channels), even though MythTV execute a channel change for such video
sources when mythbackend is started, it always executes a channel
change to the last watched channel whenever LiveTV is fired up.

Your mythbackend logfile should contain useful output on why LiveTV
fails - my guess is that it can't find the channel it is trying to
tune to, or the channel change script is not returning success/true.

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