[mythtv-users] Problem controlling external tuners in new upgrade using mythtv V0.25.3

[f-myth-users at media.mit.edu]

    > Date: Fri, 16 May 2014 09:18:26 -0500
    > From: Craig Huff <huffcslists at gmail.com>

    > I am using the contributed program "channel" for changing stations on
    > a Motorola DCT-2xxx settop box supplied by Comcast using the serial
    > port connection.

    > I am also using the contributed program "change-channel-lirc.pl" for
    > changing stations on Comcast DTAs using hardwired optocoupler isolated
    > connections to the DTAs' sensor extension ports.

    > These have worked unfailingly under Mythbuntu 10.04 (mythtv V0.23).

    > These are working without problems under my default user login from
    > the command line as well as under the mythtv login from the command
    > line.

This makes me think it's not a groups or permissions issue, but it
might still be a good idea to ensure that the mythtv user is in the
dialout group, or whatever group it is that gives it access to serial
ports.  (Can you compare /etc/group and /etc/gshadow from your 10.04
installation to your current 12.04?)

I'd ask if they had execute permission, but you say they work when
called by hand, so I presume they do.

    > Neither is working correctly when using mythtv to change stations,
    > either in live TV or for recordings.  When I test channel changes in
    > live TV mode, I get errors about missing video output and the system
    > is locked up for some time (10 seconds? 20 seconds?) before getting
    > unceremoniously dumped back to the frontend menu.  If I open up a
    > terminal session while live TV is running and change the channel that
    > way, the channel change occurs with no muss or fuss, no matter what
    > user name I am logged in as.  I am even using the exact same command
    > strings defined in the backend settings, which are fully specified
    > pathnames to the channel changing programs.

    > Under Mythbuntu 10.04 / mythtv V0.23, the tuning programs progress
    > messages were logged in the mythbackend.log, but I don't see them (or
    > anything else relating to the tuning problems) in mythbackend.log
    > under Mythbuntu 12.04 / mythtv V0.25.3.

When you say "under the mythtv login", is that via a direct login, or
via su or sudo from your normal user?  Depending on how you do the
latter, it may be inheriting some environmnt variables that aren't
present when mythtv is being run from /etc/init.d or upstart or
whatever.

Is it possible that the scripts are running with a different
environment (such as a missing $HOME) when run via mythtv as when run
by you, even if you're logged in as (or su'ed to) the mythtv user?

    > Can anyone help figure out what is going amiss?

Try replacing the calls to the scripts with calls to a script
consisting of some or all of

  #!/bin/bash
  id >> /tmp/DEBUG
  groups >> /tmp/DEBUG
  set >> /tmp/DEBUG
  printenv >> /tmp/DEBUG

and see if you get the same results when you call it as you, as the
mythtv user, and as when myth itself tries to change channels.  If you
don't, try either changing the scripts' environments to match the
by-hand calls and see if they work, or try changing the by-hand
calling environment to match the mythtv environment and see if it
fails.

This will also tell you if your script is getting called at all when
mythtv tries to change channels, of course; maybe myth isn't even
trying.