Waveform analysis/Doh ray me: Difference between revisions
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Actual average frequency = 385.4 Hz (Soh-)
</pre>
=={{header|Vlang}}==
{{trans|go}}
As an example, we analyze the .wav file (notes.wav) created by the [[https://rosettacode.org/wiki/Musical_scale#Vlang Musical Scale]] task.
<lang vlang>import os
import math
import encoding.binary
const (
freqs = [261.6, 293.6, 329.6, 349.2, 392.0, 440.0, 493.9, 523.3]
notes = ["Doh", "Ray", "Mee", "Fah", "Soh", "Lah", "Tee", "doh"]
)
fn get_note(freq f64) string {
mut index := freqs.len
for i in 0..freqs.len {
if freq <= freqs[i] {
index = i
break
}
}
match index {
0 {
return "Doh-"
}
freqs.len {
return "doh+"
}
else {
if freqs[index]-freq <= freq-freqs[index-1] {
return '${notes[index]}-'
}
return '${notes[index-1]}+'
}
}
}
fn main() {
mut file := os.open("notes.wav")?
defer {
file.close()
}
mut hdr := []byte{len: 44}
file.read(mut &hdr)?
// check header parameters
sample_rate := int(binary.little_endian_u32(hdr[24..28]))
println("Sample Rate : $sample_rate")
data_length := int(binary.little_endian_u32(hdr[40..]))
duration := data_length / sample_rate
println("Duration : $duration")
mut sum := 0.0
sample_rate_f := f64(sample_rate)
mut data := []byte{len: sample_rate}
nbytes := 20
println("Bytes examined : $nbytes per sample")
for _ in 0..duration {
file.read(mut &data)?
for i := 1; i <= nbytes; i++ {
bf := f64(data[i]) / 32
freq := math.asin(bf) * sample_rate_f / (f64(i) * math.pi * 2)
sum += freq
}
}
cav := sum / (f64(duration) * f64(nbytes))
println("\nComputed average frequency = ${cav:.1} Hz (${get_note(cav)})")
sum = 0.0
for i in 0..freqs.len {
sum += freqs[i]
}
aav := sum / f64(freqs.len)
println("Actual average frequency = ${aav:.1} Hz (${get_note(aav)})")
}</lang>
{{out}}
<pre>
Sample Rate : 44100
Duration : 8
Bytes examined : 20 per sample
Computed average frequency = 387.1 Hz (Soh-)
Actual average frequency = 385.4 Hz (Soh-)</pre>
=={{header|Wren}}==
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