[mythtv-users] Working around a lack of a IR Blaster

stefan_jones at comcast.net stefan_jones at comcast.net
Sun Nov 22 22:55:04 UTC 2009

> From: "Nick Morrott" <knowledgejunkie at gmail.com> 
> To: "Discussion about mythtv" <mythtv-users at mythtv.org> 
> Sent: Sunday, November 22, 2009 10:30:27 AM GMT -08:00 US/Canada Pacific 
> Subject: Re: [mythtv-users] Working around a lack of a IR Blaster 
> 2009/11/22 <stefan_jones at comcast.net>: 
> > I don't have a working IR Blaster but want to record a few select shows. 
> > 
> > Shouldn't this work? 
> > 
> > Set up Analog video tuner card. 
> > 
> > Configure Input Connection to set tuner to a given channel (3). 
> > 
> > Connect output of STB to tuner. Set the STB to the desired channel. 
> > 
> > Put some dummy command in the outside tuner command line. 
> Using /bin/true is the recommended way to 'fool' MythTV into thinking 
> channel changing was successful in this scenario. 
> > Record anything in the appropriate time slot to make the tuner record from 
> > the STB for the appropriate length of time. 
> > 
> > Now, I tried this out this afternoon. First I tried watching Live TV on the 
> > Analog tuner. I saw the appropriate channel . . . the one that the STB was 
> > tuned to. 
> Expected if you have one or more tuners in the machine and (if more 
> than 1 tuner) you configured the analog tuner's input connection 
> _last_ in mythtv-setup. This gives the tuner the lowest recording 
> priority (as long as you have not made any other tuner/channel/LiveTV 
> priority changes) and will be used first for LiveTV. 
> > Then I tried a test record. No dice. If I'm looking at the right messages, 
> > another (digital) channel tried to tune in. 
> This is again expected if the digital tuner(s) has a higher priority 
> for _scheduled_ recordings. If you want to test the analog tuner for 
> scheduled recordings, you need to tell the scheduler to prefer to use 
> the analog tuner over other possibly higher-preference inputs. You can 
> do this in the scheduling options for each recording rule where you 
> want this to be the case. 
> > Do I need to "scrub" the channels for the video source so they have no 
> > tuning information? It seems to me that the Input Connection's channels just 
> > need to supply a channel number . . . no tuning information that might cause 
> > a digital tuner to try to take over. 
> If you are using a video source that relies on using an external 
> channel change script, you need to ensure that each channel configured 
> on that input has a valid frequency value. In the case of controlling 
> an STB, it is the digits you want passed to the changer script. 
> A lack of tuning information will cause the recording to fail - 
> another tuner will not try to take over. 

Thanks, I think I've got things working. 

For posterity: 

* The error messages from the digital recorder in the mythfrontend console output were a red herring. I have two "ghost tuners" from a previous install. They don't show up in mythtvsetup, but their being in the DB causes errors on exit from mythtvsetup ("Tuner 8 is pointed at channel 71 which doesn't exist") and when mythfrontend starts up. I guess I'll have to use SQL to remove them. 

* I changed priorities so that the analog tuner is 0, and the three digital tuners ranked 1,2 and 3. 

* I removed all of the channels from the analog card's lineup that overlap with the digital card's range. (The digitals listen to the clear QAM stations on the cable signal . . . essentially the broadcast HD lineup plus SD digital versions of the low-tier cable TV channels; I added a "D" to the channel number to differentiate them. The analog tuner has its own lineup, consisting of the upper-tier cable channels that are now only viewable via the STB.) 

* I wrote a little script called changechannel.sh to plug into the external tuner command line field. It writes the cable channel passed to it to a file. I'll eventually include the date as well. This will come in handy for debugging when the IR transmitter is functional. 

* I was able to record two shows in a row. They look fine. The STB has a nice strong analog signal for the PVR-150 to pick up. 

Thanks again. 

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