[mythtv-users] Possible to change channels via USB?/(now firewire)

Jeff Bryner jeff at jeffbryner.com
Fri Dec 18 18:08:25 UTC 2009

Rod Smith <mythtv at rodsbooks.com> says:

> On Thursday 17 December 2009 01:28:31 pm Jeff Bryner wrote:
>> I'm struggling with firewire off a dch3200. I can get it to change
>> channels and stream, but sometimes it dies (one channel is fine, one
>> is bad, back to first and it's fine, later it all fails).
> I've run into some of that, too, but it tends to stabilize significantly in
> normal use, vs. testing use. It's also unreliable in live TV mode for some
> reason.
>> How do you do just the channel change via firewire? I'm thinking it's
>> time to revert to that and record via my pchdtv tuner card.
> Here's my basic FireWire tuning script. You'll almost certainly have  
> to change
> the video device file and/or its input, and the GUID for your cable box
> (0023eefffea7cda7 in the below). I've also had problems in the past with
> razzy audio from the tuner card, which can be gotten around by tuning to a
> regular (coax) channel, copying some data to /dev/null, and tuning back to
> the S-video input. I've commented out those lines below, but if you
> experience bad audio, you should uncomment them or try something similar.
> Note that the 3200ch script is my modified 6200ch program. The original
> 6200ch comes with the MythTV source code, in contrib/channel_changers (or it
> did come with 0.21; I haven't checked the 0.22 source tree). I needed to
> modify it to recognize my Motorola DCX3200-M, but I think the DCH3200 was
> supported in the version I used as a starting point.
> ------------- FireWire channel-change script ---------------
> #!/bin/bash
> # Script to change the channel on the cable box using FireWire
> # Set the tuner to the coax input and copy some data from it....
> #v4l2-ctl -d /dev/video-PVR500-1 --set-input=0
> #sleep 1
> #dd if=/dev/video-PVR500-1 of=/dev/null bs=1024 count=512
> # Set the input back to S-video....
> v4l2-ctl -d /dev/video-PVR500-1 --set-input=1
> # Change the channel for the specified cable box....
> /usr/local/bin/3200ch -g 0023eefffea7cda7 $1

Thanks for that! Yeah, I'm also fighting random firewire node changes,  
so changing via GUID would be easier. I'll check out the source for  

So you record via svideo. I'm assuming it's also possible to record  
just via the coax? In either case is the firewire even listed in the  
input cards or just the pchdtv card?

Of course it all worked perfectly last night, live tv, recording, etc.  
Not a hitch...arghh.

More information about the mythtv-users mailing list