[mythtv-users] mythfrontend suddenly became very slow to read lirc input

[Marc MERLIN]

On Sun, Sep 20, 2015 at 11:08:51PM -0700, Marc MERLIN wrote:
> (cc on replies appreciated, thanks)
> 
> I have an admittedly outdated mythtv 0.25.0+fixes.20120622 which has
> been working well enough for 3 years, but it just started being super
> slow responding to remote keys at the main menus.
> Something like 3-5 seconds for each key down press to be registered.
> 
> Once I'm playing a video, remote keypresses are instant, so mythfrontend
> passes keys fine when playing video but not when displaying its menu
> options.
> If I use the plugged in keyboard up/down from the keyboard instantly
> goes to prev/next menu option.
> 
> If I use vnc to connect to my X server running mythfrontend, I can also
> instantly move to next/prev menu options.
> 
> But if I go back to the remote, it takes seconds. If I push down 3
> times, it goes down 3 times, just takes seconds for it to happen (all 3
> at once).
> 
> lirc seems to work fine:
> myth:~# irw
> 000000008001006c 00 KEY_DOWN devinput
> 0000000080010067 00 KEY_UP devinput
> It shows that the keys are instantly received and output to clients, be
> it irw or mythfrontend.
> 
> So it seems that mythfrontend has decided to just hang before reading
> from lirc, or read from lirc and wait a while before doing anything with
> input commands, but only when displaying its menus. Once it plays
> videos, then it's fine.
> 
> Kernel is 4.1.3 on ubuntu lucid (yes, that's old too, but I don't
> upgrade things that work and need to keep working, and I'm not even
> going to go through the list of things that ubuntu changed/broke for me
> in new versions).
> 
> Considering I changed nothing with my config that I can think of, I'm a
> bit at a loss of how to debug this further.
> 
> Any idea what to try next?

Well, this is embarassing.
The same exact problem happened to me on 25 Nov 2012 and I found the
reply to my own post after looking harder.
 
But: upgrading libqt from 4.7 to 4.8 breaks in the subtle way I
described. I had just installed vlc, and that upgraded libqt which then
broke mythfrontend.

Still, the weirdest bug I've ever seen...

To make sure I don't get bitten again:
dpkggrep libqt4 | awk '{print $1}' | while read pkg; do echo "$pkg hold" | dpkg --set-selections; done

Marc
-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/                         | PGP 1024R/763BE901