Comment 7 for bug 971429

Thank you for adopting this.
In general, this is a good start to read:
http://www.mixxx.org/wiki/doku.php/bugfix_workflow

You can put a minimum check somewhere here:
https://github.com/mixxxdj/mixxx/blob/master/src/library/autodj/autodjprocessor.cpp#L505
And call:
https://github.com/mixxxdj/mixxx/blob/master/src/library/autodj/autodjfeature.cpp#L278
The preference option can be placed here:
https://github.com/mixxxdj/mixxx/blob/master/src/dlgprefautodj.cpp

Do not hesitate to ask for more help.

By the way: Bug #1394928 is related and might be a nice starter bug.