ebiten/examples/sinewave/main.go

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// Copyright 2016 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.
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//go:build example
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// +build example
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package main
import (
"fmt"
"log"
"math"
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"github.com/hajimehoshi/ebiten/v2"
"github.com/hajimehoshi/ebiten/v2/audio"
"github.com/hajimehoshi/ebiten/v2/ebitenutil"
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)
const (
screenWidth = 640
screenHeight = 480
sampleRate = 48000
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frequency = 440
)
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// stream is an infinite stream of 440 Hz sine wave.
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type stream struct {
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position int64
remaining []byte
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}
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// Read is io.Reader's Read.
//
// Read fills the data with sine wave samples.
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func (s *stream) Read(buf []byte) (int, error) {
if len(s.remaining) > 0 {
n := copy(buf, s.remaining)
s.remaining = s.remaining[n:]
return n, nil
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}
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var origBuf []byte
if len(buf)%4 > 0 {
origBuf = buf
buf = make([]byte, len(origBuf)+4-len(origBuf)%4)
}
const length = int64(sampleRate / frequency)
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p := s.position / 4
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for i := 0; i < len(buf)/4; i++ {
const max = 32767
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b := int16(math.Sin(2*math.Pi*float64(p)/float64(length)) * max)
buf[4*i] = byte(b)
buf[4*i+1] = byte(b >> 8)
buf[4*i+2] = byte(b)
buf[4*i+3] = byte(b >> 8)
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p++
}
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s.position += int64(len(buf))
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s.position %= length * 4
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if origBuf != nil {
n := copy(origBuf, buf)
s.remaining = buf[n:]
return n, nil
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}
return len(buf), nil
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}
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// Close is io.Closer's Close.
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func (s *stream) Close() error {
return nil
}
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type Game struct {
audioContext *audio.Context
player *audio.Player
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}
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func (g *Game) Update() error {
if g.audioContext == nil {
g.audioContext = audio.NewContext(sampleRate)
}
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if g.player == nil {
// Pass the (infinite) stream to NewPlayer.
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// After calling Play, the stream never ends as long as the player object lives.
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var err error
g.player, err = g.audioContext.NewPlayer(&stream{})
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if err != nil {
return err
}
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g.player.Play()
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}
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return nil
}
func (g *Game) Draw(screen *ebiten.Image) {
msg := fmt.Sprintf("TPS: %0.2f\nThis is an example using infinite audio stream.", ebiten.ActualTPS())
ebitenutil.DebugPrint(screen, msg)
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}
func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
return screenWidth, screenHeight
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}
func main() {
ebiten.SetWindowSize(screenWidth, screenHeight)
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ebiten.SetWindowTitle("Sine Wave (Ebiten Demo)")
if err := ebiten.RunGame(&Game{}); err != nil {
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log.Fatal(err)
}
}