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

[Stephen Worthington]

On Sat, 28 May 2016 15:26:51 +1200, you wrote:

>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.

I missed the %CHANID% field in the table - that would be better to
pass to the script than %RECID%.  You would still need to map that to
the channel number you need to send to the STB.  I would be fairly
easy to lookup the channel database for that CHANID and get the
corresponding channel number.