1. Java Beat Detection Program A Java Application Based on Eric Scheirer and Others

2. Sources Tempo and Beat Analysis of Acoustic Musical Signals by Eric Scheirer Beat Detection Algorithms by Frederic Patin http://www.gamedev.net/reference/programming/features/ beatdetection/ Beat This: A Beat Synchronization Project by Cheng, Nazer, Uppuluri, Verret http://www.owlnet.rice.edu/~elec301/Projects01/beat_sync /beatalgo.html

3. Program Input Wav file –8-bit –Mono –22050 samples/sec

4. Step 1: FFT Performed on sliding frame of 1024 samples. With each step, the frame moves forward 256 samples (so chunks overlap) Resolution of 16.1 ms Min frequency of 22.5 Hz

5. FFT (cont.) Frequency outputs are grouped into 9 bands –Varying sizes, as suggested by Patin Different from Scheirer and Beat This web site –Use half-hanning window for smoothing

6. Differentiation Scheirer’s method for finding onsets in each band For each band, at each frame, compute Diff[band][f] = BandData[band][f]-BandData[band][f-1]; Half-wave rectify If(BandData[band][f] <0) BandData[band][f] = 0; This gives a picture of sudden increases in each band

7. Peak Finding Start a few seconds into the recording (for comb filter, explained next) Take a window of about 20 frames. Sum frequency data across bands. Consider the peak to be our first estimation of a beat

8. Comb Filter Alternate to autocorreclation described by Scheirer for finding periods of repetition. I use a simplified method – seems to work better than Scheirer’s or Beat This.

9. Comb Filter (cont.) Given a starting time t, For each band, b, and for every candidate period T: CF(T) = Diff[t] + Diff[t-T] + … + Diff[t-nT] Sum results across bands Maximum value is the new estimate for the music’s rhythmic period.

10. Peak Finding + Comb Filter When we find a peak at time t Estimate period T starting from t. Begin looking for a new peak in the neighborhood of t+T. Repeat: find peak, find period, find peak, find period… until the end of the data.

11. Results St. Etienne Chemical Brothers Beethoven Tito Puente

12. Questions?