beginning work on equalizer

player/equalizer.go

@@ -0,0 +1,57 @@
+package player
+
+import (
+	"fmt"
+	"strings"
+)
+
+type WidthType int
+
+const (
+	WidthTypeHz WidthType = iota
+	WidthTypeKhz
+	WidthTypeQ
+	WidthTypeOctave
+	WidthTypeSlope
+)
+
+type EqualizerBand struct {
+	Frequency int
+	Gain      float64
+	Width     float64
+	WidthType WidthType
+}
+
+type EqualizerCurve []EqualizerBand
+
+func (e EqualizerCurve) String() string {
+	var sb strings.Builder
+	for i, band := range e {
+		if i > 0 {
+			sb.WriteString(",")
+		}
+		sb.WriteString(band.String())
+	}
+	return sb.String()
+}
+
+func (e EqualizerBand) String() string {
+	return fmt.Sprintf("equalizer=f=%d:g=%0.2f:t=%s:w=%0.2f",
+		e.Frequency, e.Gain, e.WidthType.String(), e.Width)
+}
+
+func (w WidthType) String() string {
+	switch w {
+	case WidthTypeHz:
+		return "h"
+	case WidthTypeKhz:
+		return "k"
+	case WidthTypeQ:
+		return "q"
+	case WidthTypeOctave:
+		return "o"
+	case WidthTypeSlope:
+		return "s"
+	}
+	return "x" // not reached
+}