13.4. Beat Detection
Mixxx uses an ultra-precise BPM and beat detector. Manual adjustments are redundant in many cases because Mixxx knows where the beats are.
BPM and beat detection is a complex operation. Depending on your computer and the track's bitrate and duration this may take some time. By default Mixxx analyzes the complete track. To accelerate beat detection on slower computers, a “Fast Analysis” option is available. If enabled, the BPM is computed by analyzing the first minute of the track. In most cases this does not affect the beat detection negatively because most of today's dance music is written in a 4/4 signature with a fixed tempo.
The table below summarizes the beat detection settings:
Enable Fast Analysis
If enabled, BPM will be detected by only using the first minute of audio.
Assume constant tempo
If enabled, Mixxx assumes that the distances between the beats are constant. If disabled, the raw beat grid obtained by the analyzer is presented. The latter is appropriate for tracks with variable tempo.
Enable Offset Correction
Prevents beat markers from being placed incorrectly.
Re-analyze beats when settings change or beat detection data is outdated
If enabled, Mixxx over-writes old beat grids from prior versions. Moreover, it will re-analyze the BPM if your beat detection preferences change or BPM data from 3rd party programs are present.
Correcting Beat Grids
There may be situations where BPM and beat detection do not result in a proper beat grid.
Typically, the detected BPM is correct but the analyzer has failed to detect the location of the first beat. Consequently, the beat markers are shifted, i.e. the beat markers are a fixed distance from the true beat. To adjust the beat grid, cue the track before a real beat and click the Beat-grid Adjust button in the Deck Options Button Grid.
If the detected BPM is not accurate, the corresponding beat grid will also be inaccurate. A deviation of 0.02 BPM units from the correct BPM will cause beatgrid alignment issues on long tracks (e.g. a club mix). If this happens, your beatgrid may look aligned for the few minutes but you will notice a slight drift as the song goes on. Finding the correct BPM is easy in many cases - just follow the note below.
If the detected BPM value is not sufficiently accurate but very close to an integer value, try to set the BPM value manually to the integer.