[mythtv-users] Dual tuners with different channels

Brad Templeton brad+myth at templetons.com
Tue Dec 7 23:05:05 UTC 2004

On Tue, Dec 07, 2004 at 04:16:37PM -0600, Mark Friedgan wrote:
> yes on 2, no on 1
> > > 1. Is there a way for MythTV to detect if the cable box power is on, and
> > > turn it on if necessary? Simply leaving the cable box on all the time is
> > > not necessarily an option, as sometimes the cable company uploads firmware
> > > upgrades, and that causes the box to reboot, and sometimes shutdown.

Well, depends on how much programming you want to do.  In fact, it
seems that, if you know how the drivers work, it should be a relatively
straightforward job to detect if audio and video are coming out the
jacks of the cable box.   Audio is probably simpler but could be fooled
by an occasional silence, or being tuned to a silent channel (digital
cable systems do have these)  Video on the other hand should be obvious.
If the box is off there is no sync signal, a fat zero out the video jacks.

(Some drivers for RF tuners also have a signal strength meter, if you
wanted to receive the signal on channel 3, in spite of the degredation
of going through RF.   If you can't detect the video signal you could also
throw in a $10 analog tuner card if the driver will tell you signal strength.
That would at least tell you if the cable box is on!)

Anyway, if you can put together a detector for this, you could then
modify your ir blasting program to detect, and if it sees zero to issue
the on/off code, and channel code, and then check again.

You could also just write a program that wakes up every few minutes when
not recording and checks for audio over a long cycle, and if it doesn't
get it, turns the box on and tunes to a channel sure to have audio.
(If audio detection is your best bet.)

Satellite and cable boxes are a royal pain.  My satellite box, for
example, as some "interactive" channels which take over the number pad,
so numbers no longer change the channel!   To get out of them and get
to another channel you need to go to the program guide and then move
out.   I don't know what idiots designed this appraoch.

Because of that, I give up on ir-blaster tuning.  Instead, I put timers
in the satellite box, which force it to tune my shows.  If the shows
move I can be out of luck.  (I also IR blast which doesn't tend to hurt,
so it generally works.)   Many boxes have this as a means of helping you
record to VCR.

But analog cable is much nicer when it comes to any kind of recorder -- tivo,
vcr or myth.

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