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LMMS segfaults and there are no error messages on the console. How do I get debugging information?

Use the GNU Debugger:

:~$ gdb lmms
GNU gdb 6.X
Copyright (C) 2006 Free Software Foundation, Inc.

(gdb) r
Starting program: lmms

If a segfault happens, LMMS will freeze and you'll get some information on the terminal. Entering bt or bt full will show a backtrace you can report.

Make sure you have debugging symbols in LMMS. That usually means compiling with the -g flag and not stripping the symbols afterwards.

I get lots of latency (lag) when playing instruments in LMMS

This is often the cause of your sound being routed through PulseAudio (which is the default for many desktop distributions such as Ubuntu), even if you have set the audio interface to ALSA. To fix this problem, LMMS needs to directly access your sound card. To do this, run

aplay -l

And look at the card and device numbers - for example:

card 2: SI7012 [SiS SI7012], device 0: Intel ICH [SiS SI7012]

Next, go to LMMS, open the settings menu (Edit > Settings), go to the Audio Settings tab, and in the "device" field, delete "default" and type


Where the first "x" is the card number, and the second is the device number. For example, the above configuration would be "hw:2,0". Restart LMMS and you should have very little latency.

Note: This will make LMMS take over your sound card; no other application will be able to make sound while LMMS is running.

When I try to play one of the demo-songs the sound gets crapped. What can I do?

If you're using OSS you can try to use ALSA instead, because using OSS with LMMS is known to lead to problems in some cases. If this doesn't help, your computer is probably too slow to render all the data in realtime. So you can try to export the project as WAVE/OGG-file and play that. Even if you can't play the song in realtime, it's possible to render and export it to a file, which you can then listen with any music player.

Another thing is the internal buffer-size, used by LMMS. The smaller this value the smaller the latency. If you have problems because of low performance, you can try to increase the buffer-size. Then LMMS renders more data at one time and interrupts aren't always spurious... Use the setup-dialog to change this parameter.

You can also try to re-compile LMMS with tuning-options according to your platform. Setting compile flags may help.

To set optimizing compile flags, run this command before running cmake:

export CXXFLAGS="-O3 -march=native"

As soon as I start LMMS it eats all my CPU-time. Is that normal?

You're using a quite old version of LMMS which had this bug. Try to upgrade LMMS and everything should be alright...

When using JACK as audio-interface, there's no sound. What to do?

You probably didn't start JACK-transport. Start an application like qjackctl and click on "play" or whatever it is named in your application. Then everything should be alright. Actually LMMS automatically should start JACK-transport on startup. You may also need to connect lmms to your sound card, using the patch bay in qjackctl.

I compiled LMMS with VST-support but it doesn't work at all

Make sure you didn't pass -fomit-frame-pointer in a FLAG-parameter to configure. This is known to lead to an unusable LVSL (LMMS VST Support Layer).

Plugins don't load on 64bit platforms

The path to the plugins directory is (as of v. 0.3.0) hardcoded, meaning that you'll have to manually setup a link from the right place, to the expected place:

- open a terminal
- type "su -"
- enter the password for root
- type "ln -s /usr/lib64/lmms/ /usr/lib/lmms"

And you're ready to go. Someone should fix this (hint: src/core/config_mgr.cpp ;-) )