[mythtv-users] dvb-t modulator instead of hdpvr

[Stephen Worthington]

On Fri, 27 May 2016 21:46:05 +0100, you wrote:

>On 27/05/16 19:03, Yianni Vidalis wrote:
>>
>>
>>
>> Hi, there was a discussion abour hdpvr2 replacement some weeks ago http://www.gossamer-threads.com/lists/mythtv/users/597893 and there was a very promising post about a hdmi modulator ( http://www.gossamer-threads.com/lists/mythtv/users/597893#598060 ).
>>
>> My own cherished hdpvr has been misbehaving lately and I've ordered a replacement power adaptor, in hope that its not the unit itself that's misbehaving (it will be the third power adapter for this unit).
>> In case of providers that don't use HDCP, how could one use such a modulator? If it transmits on a certain UHF channel I guess I should use a standard dvb-t adaptor but which shouldn't tune to other channels, isn't this correct? And I should use the same channel changing script on the stb.
>> What kind of adapter should I add to mythtv to use such setup? Dvb-t cards don't offer the channel changing script field in mythtv-setup.
>> Any help would be really appreciated.
>>
>You shouldn't need the channel changing script in that case. Treat it just like a station that 
>transmits on only one channel, which it is: you have to scan it in the normal way. If the 
>modulator's output is compatible, then your scan should find it and set up a single channel in the 
>table.

Yes, but he still needs the channel changing script to change the
STB's channel.

In the database, the externalcommand field is still present even for
DVB-T tuners.  So I did an experiment on my test box (running Ubuntu
16.04 / MythTV 0.28-fixes), putting a command into that field that
logged to a log file when it was called.  Unfortunately, it seems that
mythbackend is doing checking on that field, and when I started
mythbackend and it tested all the tuners, I got a warning message:

recorders/channelbase.cpp:677 (InitializeInput) ChannelBase[1]:
External Channel changer is set, but this device does not support it.

And there was no output to my log file, so it looks like that will not
work.  Which is a pity as it would be much easier to use than the
recording started event.

So I then tried using the same test using the recording started event
(EventCmdRecStarted), and, as expected, that worked.  So it looks like
you will need to use the EventCmdRecStarted or EventCmdRecPending
event hook to call your channel change script.  You would need to pass
the %CARDID% and %RECID% fields to the script, and in the script use
them to check that the card was the DVB-T tuner, then use the RECID to
look up the database for the channel you want.  Or you could pass the
%FILE% parameter and parse the start of the filename to get the
channel.

See here for events:

https://www.mythtv.org/wiki/MythTV_System_Events

Let me know if you need help with getting this to work.