[mythtv] Shouldn't MythTV disable the tuner between switching inputs?

David Backeberg dbackeberg at gmail.com
Mon Jan 7 14:15:07 UTC 2008

>Anyhow, when I'm attaching a device to a/v
>connectors on a PVR-150, and I'd like to watch Livetv
>through that, instead of the tuner, I can't seem to
>change my inputs on the card because the tuner isn't
>being shut off first (I have programming on the tuner,
>so I want to keep that input source).  I'm just asking
>if it's not better to have Mythtv shut off the tuner
>before switching away from it to a different input.

So I don't know if this is still true, but it used to be that when you
downloaded the ivtv sources (before mainline kernel adoption) the
sources came with several contributed scripts. One of these was a
command-line utility that accepted an argument and changed a tuner
channel for you. MythTV accepts preferences to use an external command
for changing a tuner channel. (This is how people with external tuners
change channels on those tuners.) I actually used this utility with my
PVR250 and Myth for a long time. If at a command line, outside of
myth, you could say something like
./change_channel 33
and then
cat /dev/video0 > myfile.mpg
or whatever, and you could use this to record from your card without a
special program. Also, Myth itself would provide the argument to
change to the requested channel if you wanted to do tuner changes with
Myth and you set your preferences accordingly.

So my question: does that command line utility let you flip to the
composite inputs? I don't have a PVR150 to find out. If so, voila,
just add another channel and set the name to whatever argument the
command-line utility wants. And if the utility doesn't let you do
that, the source is there, and it shouldn't be too hard to change the
code, right? And this won't break your regular channel changes.

I agree with other devs who think that Myth itself should be
tuner-card agnostic and not have special code for a particular card.
We should let the tuner experts manage changes in the tuner driver, as
they're the most knowledgeable about how those internals work.

One last question: If you didn't have Mythtv, and you just had the
PVR150, how would you change from tuner channels, to the composite
inputs, and back again?

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