Beat Calculator Example
To make full use of GDAM's beat information-aware features, you must determine the beat information which describes your favorite songs. The primary tool to assist with this task is the beat calculator. Given an estimation of the bpm and firstbeat location for a song, the beat calculator will graphically display predicted beats over a picture of the waveform. These can be stretched and moved until (if possible) the bars correctly predict each beat.
This is a step-by-step journal of using the beat calculator to find firstbeat and bpm values which describe a song.
Find a promising song, and drop it onto the beat calculator. Alternately, use the arrow button to import the currently selected song from the song selector. After a short delay, an image of the song's waveform is displayed.
I use the middle mouse button to set the position marker (vertical red line) near the beginning of the song. I press play, and listen for the first measure of the song. Noting the time (five and a half seconds of introduction on this track) i begin to click on the tap button in time with the music. After a minute or so, the bpm value given by the timing of my taps has closed in on a reasonable first estimate.
I enter my first guess at the tempo of the song and the location of the first beat. Yellow bars appear on the image where beat locations are predicted. I zoom in close to the first beat, and play the song from there. This time, i can hear a clicktrack marking the locations of the beat lines.
A closer look supports what my ears told me: the beats are predicted a little early of their actual location.
I control-click on the actual location of the first beat, and the bars jump into alignment. I can hear the clicks move much closer into synch with the music.
Moving further into the song, I see that my bpm estimate is too high; the clicks are getting ahead of the music.
I left-click on precise beat locations, and the bpm value is nudged down so that the beat lines fall on my mouse press locations.
I continue through the song, improving the bpm estimate, until i reach the end.
I return to the first beat, zoom in closer, and make another pass through. Shift-click is used to shift the first beat location slightly without disturbing the bpm value. I also verify that the clicks are reasonably accurate throughout the entire song. When i'm happy with the values, i use the update database button to write the bpm and firstbeat data into the database. I'll save the database so the data will forever be available.
