Troubleshooting FAQ

Being able to lower the Latency slider in Mixxx's Sound Hardware Preferences as much as possible makes a huge difference in its responsiveness. Here are some tips to help you do that.

• Disable CPU Frequency Scaling or use the 'Performance' mode. CPU Frequency Scaling is a main cause of Mixxx skipping on laptops. (Do ps aux | grep cpufreq and kill any processes you find.) – Actually it is better to remove the kernel modules, do `lsmod | grep freq` and then remove each of the modules using rmmod, note that if you are using a notebook it will burn through battery much quicker when doing this.
• Disable chipcard2. This utility polls for smart cards every few seconds, and when it does, it can cause Mixxx's audio to skip, even with the latency set really high.
• If you're using ALSA, try setting your Master output hardware to just “default” instead of specific hardware. (This made a huge difference on a test system with integrated Intel soundcard.) The drawback to this is that system sounds (KDE beeps and such) will now be mixed in and will come out the main output.
• You can also try using a real-time kernel or a distribution that includes one, like 64Studio or Ubuntu Studio. Note that you will need to set up real-time support (scroll down to "Real-time support") for audio applications in order to gain any benefit from a real-time kernel.

• Use the ASIO sound API in Preferences This requires that you have ASIO drivers installed for your sound hardware. If not, search for them at the web sites of your sound card manufacturer and/or the chipset manufacturer (for integrated cards.) If they don't offer ASIO drivers, try using ASIO4ALL.
• Disable any anti-spyware “realtime” scanning. It's been discovered doing this for Ad-Aware makes a huge difference in latency.
• Disable anti-virus on-access scanning. This hasn't been confirmed but is worth a try since these programs are known to slow systems down in general. This is only recommended if your system is not connected to a network or the internet otherwise you put your system at risk of infection.
• Disable nVidia's “PowerMizer.” nVidia's laptop drivers have a feature called “PowerMizer” that has been reported to cause all kinds of problems for audio and overall latency. It can be disabled with a registry tweak: http://forum.notebookreview.com/showthread.php?t=261929
• Deactivate the “Microsoft ACPI-Compliant Control Method Battery” in the Device Manager (under Control Panel→System→Hardware.)

• IRQ sharing - Make sure your sound card(s) are not sharing Interrupt Request ports with any other system devices (like network cards.) If they are, try to change them in your OS or BIOS or disable the other devices while you're DJing.
  • Linux: at a console, issue cat /proc/interrupts If the line that contains the kernel module for your sound card has something else next to it, this affects you, and you may be able to change the IRQ at module load time (type man modprobe for more information on this.)
  • Windows: Open Device Manager (Start→Control Panel→System, Hardware tab, Device Manager button) find your sound card, right-click it, choose Properties, then the Resources tab. Drop down to IRQs and see if anything else is sharing it. If so, this affects you, and you can try changing the IRQ assignment for your sound card in this window.
• Increase process priority
  • As a last resort, run Mixxx as the root user or a user with administrative privileges. This allows Mixxx to increase the priority of its critical threads to real-time. This should greatly reduce latency on a busy system. Be aware that running as root/admin puts your system at greater risk from malicious code.
  • Alternately and more safely, on Linux/OSX, edit /etc/security/limits.conf and add <your user name> soft rtprio 99 to allow Mixxx (and other processes you run) to increase their thread priority to maximum, or just run Mixxx from a console with sudo mixxx.

We've updated the library Mixxx uses for BPM detection in 1.7 which helps. There's also a bug with BPM schemes that's difficult to fix in the short term, so here is a workaround in the meantime:

1. Open Options→Preferences→BPM Detection
2. Create or edit a BPM scheme with the range you want & click OK.
3. Highlight that scheme in the list.
4. Click the “Default” button. (It's only by doing this that the selected BPM scheme is activated.)

After doing that, you may need to explicitly tell Mixxx to re-analyze your files, or you can just delete your library file (see below) and it will do auto-detection the next time you load each song. If you see values half what they should be, go into Preferences→BPM Detection, and check Allow BPM above the range. Click OK, then have Mixxx try to detect it again. (Though you shouldn't need to use that checkbox if you set the scheme correctly.)

First try clicking Library→Rescan library. Then re-sort it (by artist name or whatever) by clicking on the column heading. If that doesn't help, delete your library file and restart Mixxx.

Make sure Mixxx is closed, then look for “mixxxtrack.xml” in:

• Windows: %USERPROFILE%\Local Settings\Application Data\Mixxx
• Linux/Mac OS X/BSD/Unix: ~/.mixxx

If you can't find it, search your computer for “mixxxtrack.xml”

• If on Windows, Click Start→Run, type %USERPROFILE%\Local Settings\Application Data\Mixxx and click OK. (If you want to use “Find files/folders,” make sure to open “Advanced Options” and mark “Search Hidden Files/Folders”.)
• If on Mac OSX, press Shift-Command-G or “Go to folder…” command in the Finder's Go menu. Then enter ~/.mixxx/

This also applies for the “Audio device could not be opened” error.

When no sound cards/devices appear in the sound preferences dialog or you get the “Audio device could not be opened” error, it usually means that another application is using your sound card(s). This problem only appears on Linux. To fix it, make sure no other applications are using your sound card. If your system has PulseAudio installed (Ubuntu,) you will want to run Mixxx from a console with the following command: pasuspender mixxx This suspends the PulseAudio daemon and lets it release the sound card so Mixxx can take exclusive control. Once Mixxx ends, PulseAudio takes the card over again.

If that doesn't help, the usual culprits are Firefox and the esound daemon. Closing Firefox normally will take care of the former, and running “killall esd” in a terminal will take care of the latter. If it's still not working, running “sudo fuser -v /dev/dsp*” and “sudo fuser -v /dev/snd/*” will show you the list of applications currently using your soundcards. If you're using ALSA, you can also choose the “default” sound card option which will mix Mixxx's output with everything else.

You can also go into your sound manager preferences and change the auto-suspend feature to do so after just a second or so. (In KDE Control Center, go to Sound & Multimedia, Sound System, then at the bottom of the pane, change “Auto-suspend if idle”.) This will cause the desktop to drop exclusive control of the card sooner so Mixxx can see it on startup.

Mixxx 1.5 doesn't play nicely with Beryl/Compiz, as reported by several users. This is due to some funky OpenGL code inside QT3. Fortunately, Mixxx 1.6.0 no longer uses QT3 and reportedly works very well with Beryl/Compiz.

This is a known bug with Qt and Compiz – the only solution at this time is to disable Compiz when using Mixxx. In many cases, however, the two are able to work fine together. It seems this might be specific to certain graphics hardware.

See “Mixxx behaves weird with Beryl/Compiz/Compiz Fusion” above. Thought there is some (unknown to us) extra problem with how Ubuntu uses compiz, appearently. The workaround is to go System→Preferences→Appearence→Visual Effects and set them to “none”. After you do this Mixxx should behave properly (tell us if it doesn't!).

We've seen this a few times and it has always been a video driver problem. Make sure you have the latest drivers for your card. (You may need to get them from the chipset maker (nVidia, AMD/ATI) rather than the system board or computer manufacturer, since the manufacturer drivers aren't always the latest.) Also, if you're on Windows, make sure you have the latest DirectX installed.

Before you try anything else, please update or reinstall your nVidia graphics driver. (This applies to all OSes.) I don't care if it's the same exact version, apparently it is fickle and needs to be rebuilt/reinstalled any time things change in the OS. Try this first before going any further. 90% of the time it will fix your problem. You might also try getting the latest driver from nVidia's web site instead of your PC/card manufacturer since they may be newer.

• Mobile Intel 4 Series chipset with I945/965 graphics driver sometimes causes segmentation fault on exit in Windows and Linux. This is fixed by upgrading your version of the Qt libraries on Linux or getting the latest Mixxx 1.7 package for Windows.