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18. Troubleshooting.

18.1 Illegal Instruction.

This error can happen for the following reasons:

18.2 mythfilldatabase failing.

If mythfilldatabase suddenly appears to be failing, check to see what version of XMLTV you're running. Versions prior to 0.5.4 need to have the following change made: edit the /usr/lib/perl5/site_perl/5.8.0/XMLTV/ZapListings.pm file and perform a global search and replace, searching for "tvlistings2" and replacing it with "tvlistings". NOTE: It is highly recommended to run the latest version of XMLTV available. In North America, zap2it, the listings provider, has been making numerous changes to their website which negatively impact XMLTV.

18.3 MythTV seems to disappear; can't see video

If you're using Gnome as your window manager, try switching to KDE. For Red Hat Linux 8.0 users, edit /etc/sysconfig/desktop and change "GNOME" to "KDE".

18.4 Fast CPU, choppy or jittery video.

This is most likely because your hard drive isn't setup to use DMA. Use the hdparm program to check and enable DMA.

# hdparm -d /dev/hd?
will tell you the DMA status for your hard drives. If you run hdparm with the -d1 parameter, it will turn DMA on.

You may also setup your PC to do this at boot time, either by adding the command to your /etc/rc.local file, or by adding files to /etc/sysconfig.

On Mandrake and other distributions, if you install hdparm from an RPM you will most likely get a /etc/sysconfig/harddisks file installed. This file will be parsed by the /etc/rc.sysinit script. If you use the default harddisks file, your changes will affect all IDE devices (including CD ROMs). If you wish to use different parameters for various devices, rename and/or copy the file to harddiskhda, harddiskhdb, etc. Edit the file to your liking and on the next reboot your setting will be preserved.

18.5 I keep losing all of my settings every time I compile!

MythTV will overwrite any settings in /usr/local/share/mythtv. If you want to make sure that you don't lose your modifications, make a directory ~/.mythtv and copy your mysql.txt file to this location.

18.6 Compile errors.

Some compile errors are worse than others. If you get an error that doesn't abort the compilation, and says something like:

cc1plus: warning: changing search order for system directory
"/usr/local/include"
cc1plus: warning:   as it has already been specified as a non-system
directory
then it shouldn't be a problem.

If you get an error like /usr/bin/ld: cannot find -lXext, the compiler is telling you that you don't have XFree86-devel installed, or that your distribution hasn't set it up correctly. This needs to be fixed before MythTV will compile.

18.7 My screen goes blank, but comes back when I wiggle the mouse or use the keyboard.

This is due to DPMS, the Display Power Management System, which is used to save power by turning off your monitor when the system decides that it's not being used or to a screensaver that has defaulted to a blank screen. Since it's likely that watching TV will not generate keyboard or mouse events for a time, you need to turn off DPMS and the screensaver. There are a few ways to do this. You may also need to check your BIOS for power saving modes and disable screen blanking there as well.

Edit your /etc/X11/XF86Config-4 file, and look for:

Section "ServerFlags"
    #DontZap # disable <Crtl><Alt><BS> (server abort)
    #DontZoom # disable <Crtl><Alt><KP_+>/<KP_-> (resolution switching)
    AllowMouseOpenFail # allows the server to start up even if the mouse doesn't work
EndSection

Add Option "NoPM" "true" and Option "BlankTime" "0"to the ServerFlags section.

Also, look for:

Section "Device"
    Identifier "device1"
    VendorName "nVidia Corporation"
    BoardName "NVIDIA GeForce 256 (generic)"
    Driver "nv"
    Option "DPMS"
EndSection

In this case, you would need to either delete the Option "DPMS" line, or change it to # Option "DPMS" to comment it out. The next time you start XFree this change will take effect.

Finally, check:

Section "Monitor"
    Identifier "monitor1"
    VendorName "Plug'n Play"
    HorizSync 30-85
    VertRefresh 50-160

    # Sony Vaio C1(X,XS,VE,VN)?
    # 1024x480 @ 85.6 Hz, 48 kHz hsync
    ModeLine "1024x480"    65.00 1024 1032 1176 1344   480  488  494  563 -hsync -vsync

    # TV fullscreen mode or DVD fullscreen output.
    # 768x576 @ 79 Hz, 50 kHz hsync
    ModeLine "768x576"     50.00  768  832  846 1000   576  590  595  630

    # 768x576 @ 100 Hz, 61.6 kHz hsync
    ModeLine "768x576"     63.07  768  800  960 1024   576  578  590  616
EndSection

Ensure that there isn't an Option "DPMS" in the Monitor configuration.

You can also turn off DPMS from the Command Line, but this will not survive a reboot.

$ xset -dpms

Using xset +dpms will turn it back on.

Another technique to try, which will turn off the screensaver:

$ xset s off

Finally, depending on your distribution, you may be able to turn it off from within the control panel.

18.8 I can't checkout using CVS anymore!

Isaac has changed some things around. The CVS repository is now known as cvs.mythtv.org, rather than www.mythtv.org or mythtv.org. Make sure you change your CVSROOT to point to the new server, delete your old tree, and re-do the checkout.

18.9 I get segfaults / MythTV isn't doing anything.

Without details, the developers will not be able to determine if you have discovered a genuine code-bug, or it the problem is with your system. In order to determine what's going on, you must recompile MythTV with debugging support and run MythTV within gdb, the GNU debugger.

Edit the settings.pro file. Make sure that the top of the file looks like this:

$ cat settings.pro
CONFIG += debug
#CONFIG += release

Now, you need to clear out the old versions of the software to ensure that you're running with the debugging code, then compile and install.

$ make clean distclean
$ ./configure
$ make
$ su
# make install
# exit

At this point, you now have debug-enabled software ready. Let's assume that the problem you're having is in the setup program.

$ cd setup
$ gdb ./setup

GNU gdb 5.3-1mdk (Mandrake Linux)
Copyright 2002 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i586-mandrake-linux-gnu"...
(gdb)

gdb has a number of options, read the man page for more information.

Once at the (gdb) prompt, type run to start program execution. When the program segfaults, type bt to get the backtrace. The backtrace should be posted to the mythtv-dev mailing list, along with the steps you followed to get the program to crash.

18.10 MythTV makes my system crash.

MythTV can not crash your system - it is a user-level program. If your system is crashing when you run MythTV, then you have some issue with the drivers for your capture card or other hardware, or the CPU fan has fallen off/broken and your system is overheating when asked to perform a CPU intensive task like encoding video.

18.11 Troubleshooting audio

By Bruce Markey, mailto:bjm@lvcm.com

Audio appears to be one of the bigger issues that users run into on the mailing list. If the audio isn't configured correctly, then MythTV will often appear to hang, when in fact it is trying to manipulate the audio subsystem and failing. You may or may not receive error messages indicating that the source of the error is the audio subsystem.

You can not use xawtv to determine if your audio is working correctly, since xawtv is simply using the the analog sound patched through line-in to line-out. It doesn't need to digitize the sound unless you are using the recording function.

A better test to verify that sound will work for MythTV (and recording with xawtv for that matter) is to startup xawtv, mute the line-in then run aplay /dev/dsp. You should hear the recorded audio slightly delayed behind the realtime video. Once this test succeeds, MythTV should work correctly because it writes to and read from /dev/dsp in the same way that aplay does.

To record audio along with video the audio signal must be digitized by a DSP so that the audio data can be stored in a file. On playback, the audio data is written to /dev/dsp and converted back to an analog signal. This analog signal should then be sent to your speakers. Here is what is needed in alsamixer:

CAPTUR source - the analog source to be sent to the DSP. This should be set to the input source from the tuner card to the sound card. In most cases this is Line but this could also be Aux, CD, Mic, etc., depending on how you connect the input cable. This source should be muted to prevent patching through the analog sound. The volume of this source will not affect the record level.

Capture mixer - this sets the level for the analog to digital recording. While a volume of 100% is recommended for testing, distortion may occur. Lowering this level to 75% to 85% may result in better audio quality. "Capture" should be marked as the CAPTUR destination.

PCM mixer - this sets the level for the digital to analog playback. While a volume of 100% is recommended for testing, distortion may occur. Lowering this level to 75% to 85% may result in better audio quality.

Master mixer - sets the level for the analog signal sent to line-out or the speakers.

You may also want to ensure that /dev/dsp hasn't already been grabbed by another process, like esd or artsd. If /dev/dsp isn't available, then MythTV won't work. Check your windowmanager documentation for instructions on disabling the sound manager. If you wish to see what application is grabbing a resource, you can use the fuser command:

# fuser -v /dev/dsp

To disable aRts in KDE, go to KDE->Control Center->Sound->Sound System and uncheck the "Start aRts soundserver on KDE startup" box. Run # killall artsd from the command line to stop the artsd program.

If you're using multiple sound cards and multiple tuners, use alsamixer -c 1 to work with the second sound card. The first card is #0, the second card is #1, etc.

18.12 I can't see parts of the On Screen Display.

If you're a Red Hat 8.0 user, make sure that you've followed the instructions which tell you how to modify the Themes makefile. Link.


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