Java Beat Detection Program

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Java Beat Detection Program

• A Java Application Based on Eric Scheirer and
  Others

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Sources

• Tempo and Beat Analysis of Acoustic Musical
  Signals by Eric Scheirer
• Beat Detection Algorithms by Frederic Patin
  http//www.gamedev.net/reference/programming/featu
  res/beatdetection/
• Beat This A Beat Synchronization Project by
  Cheng, Nazer, Uppuluri, Verret http//www.owlnet.r
  ice.edu/elec301/Projects01/beat_sync/beatalgo.htm
  l

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Program Input

• Wav file
• 8-bit
• Mono
• 22050 samples/sec

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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

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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

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Differentiation

• Scheirers method for finding onsets in each band
• For each band, at each frame, computeDiffbandf
  BandDatabandf-BandDatabandf-1
• Half-wave rectify If(BandDatabandf lt0)
  BandDatabandf 0
• This gives a picture of sudden increases in each
  band

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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

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Comb Filter

• Alternate to autocorreclation described by
  Scheirer for finding periods of repetition.
• I use a simplified method seems to work better
  than Scheirers or Beat This.

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Comb Filter (cont.)

• Given a starting time t,
• For each band, b, and for every candidate period
  T CF(T) Difft Difft-T Difft-nT
• Sum results across bands
• Maximum value is the new estimate for the musics
  rhythmic period.

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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 tT.
• Repeat find peak, find period, find peak, find
  period until the end of the data.

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Results

• St. Etienne
• Chemical Brothers
• Beethoven
• Tito Puente

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Questions?