func comb(b audio.Buffer, delay int) (avg, n float64) {
length := b.Len()
var (
i int
done int
)
for i = length; (i - delay) > 0; i-- {
delayed := i - delay
if delayed < 0 {
break
}
done++
avg += (float64(b.At(delayed)) + 1.0) / 2.0
}
if done == 0 {
//fmt.Println(avg, done, avg / float64(done))
return 0, 0
}
return avg, float64(done)
}
func Chunk(b audio.Buffer, combSize, combDelay int) (bpm float64) {
if combDelay >= combSize {
panic("combDelay >= combSize")
}
length := b.Len()
low := 1000.0
high := -1000.0
avg := 0.0
for i := 0; i < length; i++ {
end := i + combSize
if end > length {
end = length
}
combed, _ := comb(b.Slice(i, end), combDelay)
if combed < low {
low = combed
}
if combed > high {
high = combed
}
avg += combed
}
avg = avg / float64(length)
diff := high - avg
fmt.Println("low", low, "high", high, "diff", diff, "avg", avg)
for i := 0; i < length; i++ {
end := i + combSize
if end > length {
end = length
}
combed, _ := comb(b.Slice(i, end), combDelay)
if combed > (high - diff*0.007) {
bpm++
}
}
fmt.Println("bpm", bpm)
return
}