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Speed up cross-correlation with FFT convolution #69

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Merged
chrisn merged 1 commit into from
Sep 21, 2026
Merged

Speed up cross-correlation with FFT convolution #69

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11 changes: 5 additions & 6 deletions audio_offset_finder/audio_offset_finder.py
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@

from subprocess import Popen, PIPE
from scipy.io import wavfile
from scipy.signal import fftconvolve
import librosa
import os
import tempfile
Expand Down Expand Up @@ -195,12 +196,10 @@ def cross_correlation(mfcc1, mfcc2, nframes):
o_max = n1 - nframes + 1
n = o_max - o_min
c = np.zeros(n)
for k in range(o_min, 0):
cc = np.sum(np.multiply(mfcc1[:nframes], mfcc2[-k : nframes - k]), axis=0)
c[k] = np.linalg.norm(cc)
for k in range(0, o_max):
cc = np.sum(np.multiply(mfcc1[k : k + nframes], mfcc2[:nframes]), axis=0)
c[k] = np.linalg.norm(cc)
ccs_neg = fftconvolve(mfcc2, mfcc1[:nframes][::-1], mode="valid", axes=0)
c[o_max:] = np.linalg.norm(ccs_neg[:0:-1], axis=1)
ccs_pos = fftconvolve(mfcc1, mfcc2[:nframes][::-1], mode="valid", axes=0)
c[:o_max] = np.linalg.norm(ccs_pos, axis=1)
return c, o_min, o_max


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