[mythtv-users] Scheduling and a Part-Time Slave Backend

Nick Morrott knowledgejunkie at gmail.com
Sat Nov 15 14:19:26 UTC 2008

On 14/11/2008, Brad Benson <bbenso1 at gmail.com> wrote:
> I have a firewire-capable HD STB from Comcast and I'm experimenting with
> using that as firewire capture device in Myth.  I currently only have one of
> these boxes and the wife occasionally uses it to watch live TV.  What I'd
> like to do is set it up as a capture device on a slave backend and then set
> cron jobs to start up and shut down the backend service on that slave at
> pre-defined time intervals (e.g. start slave backend service at 8pm and stop
> slave backend service at 10 am).
> How will the scheduler react to this?  Will it detect when the slave goes
> away and re-run the scheduler to account for that?  Or will any recordings
> scheduled for the slave during its downtime just get missed?

The master backend is notified when a slave backend connects or
disconnects, and reschedules appropriately.

>  I currently have an HDHomerun and two PVR-500's in my master backend server
> so I'd like for the firewire device to provide a third concurrent HD
> recording.  However, if it's not available I'd prefer to record the SD
> version of the show on one of the PVR devices rather than miss the recording
> entirely.

If your video sources/channels are configured appropriately so that
MythTV knows the "same" station is available on multiple recording
inputs, your recordings should gracefully failover to the next
available card, if the slave machine is offline.

> Ideally I will get another of these boxes and dedicate it to Myth, but
> Comcast gets enough of my money as it is and I don't relish the idea of
> paying them an additional monthly fee just to test this out.
> Does anyone know if this will work?  Or, if not, have any other suggestions
> to accomplish what I'm trying to do?
> Funny related story:  When I first started testing this it didn't occur to
> me that someone might actually be watching live TV without using Myth so I
> just scheduled some test recordings over firewire.  I noticed that most of
> the firewire recordings seemed to be failing partway through.  A few days
> later my wife asked me why the cable box kept magically changing to a
> different channel when she was watching TV.  Of course, she was watching it
> when Myth was trying to record so it would change channel and start
> recording then she would change the channel back and interrupt the video
> stream causing my recordings to die.  Oops.

Be extra careful if you have family/friends who watch LiveTV (outside
of MythTV) when using externally tuned devices such as IR/firewire
controlled STBs. This can cause no end of fun (pain)...

Nick Morrott

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