examples/audio: Rename to pcm

examples/pcm/main.go

@@ -0,0 +1,150 @@
+// Copyright 2015 Hajime Hoshi
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"log"
+	"math"
+
+	"github.com/hajimehoshi/ebiten"
+	"github.com/hajimehoshi/ebiten/ebitenutil"
+	"github.com/hajimehoshi/ebiten/exp/audio"
+)
+
+const (
+	screenWidth  = 320
+	screenHeight = 240
+	sampleRate   = 44100
+)
+
+var audioContext *audio.Context
+
+func init() {
+	audioContext = audio.NewContext(sampleRate)
+}
+
+var frames = 0
+
+const (
+	freqA  = 440.0
+	freqAS = 466.2
+	freqB  = 493.9
+	freqC  = 523.3
+	freqCS = 554.4
+	freqD  = 587.3
+	freqDS = 622.3
+	freqE  = 659.3
+	freqF  = 698.5
+	freqFS = 740.0
+	freqG  = 784.0
+	freqGS = 830.6
+)
+
+// Twinkle, Twinkle, Little Star
+const score = `CCGGAAGR FFEEDDCR GGFFEEDR GGFFEEDR CCGGAAGR FFEEDDCR`
+
+var scoreIndex = 0
+
+func square(out []int16, volume float64, freq float64, sequence float64) {
+	if freq == 0 {
+		for i := 0; i < len(out); i++ {
+			out[i] = 0
+		}
+		return
+	}
+	length := int(float64(sampleRate) / freq)
+	if length == 0 {
+		panic("invalid freq")
+	}
+	for i := 0; i < len(out); i++ {
+		a := int16(volume * math.MaxInt16)
+		if i%length < int(float64(length)*sequence) {
+			a = -a
+		}
+		out[i] = a
+	}
+}
+
+func toBytes(l, r []int16) []byte {
+	if len(l) != len(r) {
+		panic("len(l) must equal to len(r)")
+	}
+	b := make([]byte, len(l)*4)
+	for i, _ := range l {
+		b[4*i] = byte(l[i])
+		b[4*i+1] = byte(l[i] >> 8)
+		b[4*i+2] = byte(r[i])
+		b[4*i+3] = byte(r[i] >> 8)
+	}
+	return b
+}
+
+func addNote() error {
+	size := sampleRate / 60
+	notes := []float64{freqC, freqD, freqE, freqF, freqG, freqA * 2, freqB * 2}
+
+	defer func() {
+		scoreIndex++
+		scoreIndex %= len(score)
+	}()
+	l := make([]int16, size*30)
+	r := make([]int16, size*30)
+	note := score[scoreIndex]
+	for note == ' ' {
+		scoreIndex++
+		scoreIndex %= len(score)
+		note = score[scoreIndex]
+	}
+	freq := 0.0
+	switch {
+	case note == 'R':
+		freq = 0
+	case note <= 'B':
+		freq = notes[int(note)+len(notes)-int('C')]
+	default:
+		freq = notes[note-'C']
+	}
+	vol := 1.0 / 16.0
+	square(l, vol, freq, 0.25)
+	square(r, vol, freq, 0.25)
+	b := toBytes(l, r)
+	p, err := audioContext.NewPlayer(bytes.NewReader(b))
+	if err != nil {
+		return err
+	}
+	p.Play()
+	return nil
+}
+
+func update(screen *ebiten.Image) error {
+	defer func() {
+		frames++
+	}()
+	if frames%30 == 0 {
+		if err := addNote(); err != nil {
+			return err
+		}
+	}
+	ebitenutil.DebugPrint(screen, fmt.Sprintf("FPS: %0.2f", ebiten.CurrentFPS()))
+	return nil
+}
+
+func main() {
+	if err := ebiten.Run(update, screenWidth, screenHeight, 2, "PCM (Ebiten Demo)"); err != nil {
+		log.Fatal(err)
+	}
+}