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package detect
// Decimate downsamples by averaging fixed-size blocks rather than dropping samples.
//
// Only a cheap pre-filter ahead of a coarse alignment search: averaging keeps the signal's
// overall shape, which is all a coarse search needs, where keeping every Nth sample would
// alias. Correctness of the real match still comes from re-checking at full resolution.
func Decimate(samples []float64, factor int) []float64 {
if factor <= 1 {
return samples
}
out := make([]float64, len(samples)/factor)
for i := range out {
sum := 0.0
base := i * factor
for j := 0; j < factor; j++ {
sum += samples[base+j]
}
out[i] = sum / float64(factor)
}
return out
}
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