Mythtv recording problems - a workaround

17 December 2009 By klavs 2

Since the arrival og dvb-t in Denmark, I've been playing with mythtv - with mythbackend on my qnap ts-119 (1200mhz, 512mb ram - installed debian on it), inspired by Andreas Back Aaen running mythbackend on a 400mhz Buffalo linkstation.

Unfortunately I decided to go with v0.22 (the latest), and it seems it has several issues with the dvb-t signals in this region :(

Subtitles delayed on tv2, mpeg4 streams not shown correctly, or not seekable etc. (see http://forum.recordere.dk/forum_posts.asp?TID=69424&PN=7&title=mythtv-02... for details on some of the problems and possible solutions).

Some have reported that v0.21+fixes with a few patches works like a charm.. So yes - I'm considering going back a version.. :)

One issue I've had is that mythbackend simply stops doing its job (recording).. but the backend log still logs as if it's actually doing something(except recording).. I haven't had the time to setup a new backend box (my current one is too low powered to run with gdb attached) so I can't genereate a backtrace unfortunately :(

I've reported the bug, but that's where it stands for now: http://svn.mythtv.org/trac/ticket/7647

If any of you suffer the same problem - feel free to help with information to the bug - and here's a script I wrote that restarts the backend when it freezes - I run it via cron every 5 minutes.

http://vsen.dk/files/check_mythtv.sh (remember to change paths to storage folder, and mythweb url).

The script checks status using mythweb (I've found that it doesn't answer when this problem arises - or it answers with errors) and then ensures that the backend isn't actually recording (writing anything to the storage folder).

It works rather well, as the issue is detected everytime within 5 minutes - so it saves my bacon :)

2 comments on Mythtv recording problems - a workaround

  1. Anonymous
    Sun, 01/31/2010 - 05:55
    Hi Klavs. I have the identical problem of mythbackend stopping recording on ver .22 and I've updated your bug ticket. Do you notice any particular time of day that this occurs? (After running mythfilldatabase, for instance?) There have been a few folks discussing a problem of segfaults occurring when mythfilldatabase runs. I was wondering if this problem was related to the recording issue. Also, do you have your commercials being flagged after a recording is complete, or during recording? Are you running any HD capture cards / devices? Are you running any other application using MySQL simultaneously? Perhaps if we chat a bit more, we might discover some similarity in our hardware, but so far I can't see any. I'm in North America, so everything is NTSC, plus my server is a Turion64 based SiS chipset running in a socket 754 board. I also built this in Gentoo. Eric.
  3. klavs
    Fri, 02/12/2010 - 15:05

    I set my backend to NOT run comflag while recording.

    My backend is a 1200mhz arm (a qnap ts-119) running Debian with only 512mb ram.

    I'm suspecting mythtv of having some sort of (temp) memory waste, while recording - which I think is the source of my problems.

    I'm trying to find the time to create a new setup, on a dual-atom box with plenty of memory instead and see if the problems still continue.