Data commit

Task/Musical-scale/Go/musical-scale.go

@@ -0,0 +1,67 @@
+package main
+
+import (
+    "encoding/binary"
+    "log"
+    "math"
+    "os"
+    "strings"
+)
+
+func main() {
+    const (
+        sampleRate = 44100
+        duration   = 8
+        dataLength = sampleRate * duration
+        hdrSize    = 44
+        fileLen    = dataLength + hdrSize - 8
+    )
+
+    // buffers
+    buf1 := make([]byte, 1)
+    buf2 := make([]byte, 2)
+    buf4 := make([]byte, 4)
+
+    // WAV header
+    var sb strings.Builder
+    sb.WriteString("RIFF")
+    binary.LittleEndian.PutUint32(buf4, fileLen)
+    sb.Write(buf4) // file size - 8
+    sb.WriteString("WAVE")
+    sb.WriteString("fmt ")
+    binary.LittleEndian.PutUint32(buf4, 16)
+    sb.Write(buf4) // length of format data (= 16)
+    binary.LittleEndian.PutUint16(buf2, 1)
+    sb.Write(buf2) // type of format (= 1 (PCM))
+    sb.Write(buf2) // number of channels (= 1)
+    binary.LittleEndian.PutUint32(buf4, sampleRate)
+    sb.Write(buf4) // sample rate
+    sb.Write(buf4) // sample rate * bps(8) * channels(1) / 8 (= sample rate)
+    sb.Write(buf2) // bps(8) * channels(1) / 8  (= 1)
+    binary.LittleEndian.PutUint16(buf2, 8)
+    sb.Write(buf2) // bits per sample (bps) (= 8)
+    sb.WriteString("data")
+    binary.LittleEndian.PutUint32(buf4, dataLength)
+    sb.Write(buf4) // size of data section
+    wavhdr := []byte(sb.String())
+
+    // write WAV header
+    f, err := os.Create("notes.wav")
+    if err != nil {
+        log.Fatal(err)
+    }
+    defer f.Close()
+    f.Write(wavhdr)
+
+    // compute and write actual data
+    freqs := [8]float64{261.6, 293.6, 329.6, 349.2, 392.0, 440.0, 493.9, 523.3}
+    for j := 0; j < duration; j++ {
+        freq := freqs[j]
+        omega := 2 * math.Pi * freq
+        for i := 0; i < dataLength/duration; i++ {
+            y := 32 * math.Sin(omega*float64(i)/float64(sampleRate))
+            buf1[0] = byte(math.Round(y))
+            f.Write(buf1)
+        }
+    }
+}