ebiten/audio/audio.go

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// 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.
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// Package audio provides audio players. This can be used with or without ebiten package.
//
// The stream format must be 16-bit little endian and 2 channels.
//
// An audio context has a sample rate you can set and all streams you want to play must have the same
// sample rate.
//
// An audio context can generate 'players' (instances of audio.Player),
// and you can play sound by calling Play function of players.
// When multiple players play, mixing is automatically done.
// Note that too many players may cause distortion.
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package audio
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import (
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"io"
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"runtime"
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"sync"
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"time"
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"github.com/hajimehoshi/ebiten"
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"github.com/hajimehoshi/ebiten/audio/internal/driver"
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)
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type players struct {
players map[*Player]struct{}
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sync.RWMutex
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}
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const (
channelNum = 2
bytesPerSample = 2
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// TODO: This assumes that channelNum is a power of 2.
mask = ^(channelNum*bytesPerSample - 1)
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)
func min(a, b int) int {
if a < b {
return a
}
return b
}
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func (p *players) Read(b []byte) (int, error) {
p.Lock()
defer p.Unlock()
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if len(p.players) == 0 {
l := len(b)
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l &= mask
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copy(b, make([]byte, l))
return l, nil
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}
closed := []*Player{}
l := len(b)
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for p := range p.players {
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err := p.readToBuffer(l)
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if err == io.EOF {
closed = append(closed, p)
} else if err != nil {
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return 0, err
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}
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l = min(p.bufferLength(), l)
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}
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l &= mask
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b16s := [][]int16{}
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for p := range p.players {
b16s = append(b16s, p.bufferToInt16(l))
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}
for i := 0; i < l/2; i++ {
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x := 0
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for _, b16 := range b16s {
x += int(b16[i])
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}
if x > (1<<15)-1 {
x = (1 << 15) - 1
}
if x < -(1 << 15) {
x = -(1 << 15)
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}
b[2*i] = byte(x)
b[2*i+1] = byte(x >> 8)
}
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for p := range p.players {
p.proceed(l)
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}
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for _, pl := range closed {
delete(p.players, pl)
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}
return l, nil
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}
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func (p *players) addPlayer(player *Player) {
p.Lock()
defer p.Unlock()
p.players[player] = struct{}{}
}
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func (p *players) removePlayer(player *Player) {
p.Lock()
defer p.Unlock()
delete(p.players, player)
}
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func (p *players) hasPlayer(player *Player) bool {
p.RLock()
defer p.RUnlock()
_, ok := p.players[player]
return ok
}
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func (p *players) seekPlayer(player *Player, offset int64) error {
p.Lock()
defer p.Unlock()
return player.seek(offset)
}
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func (p *players) playerCurrent(player *Player, sampleRate int) time.Duration {
p.RLock()
defer p.RUnlock()
sample := player.pos / bytesPerSample / channelNum
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return time.Duration(sample) * time.Second / time.Duration(sampleRate)
}
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// TODO: Enable to specify the format like Mono8?
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// A Context is a current state of audio.
//
// The typical usage with ebiten package is:
//
// var audioContext *audio.Context
//
// func update(screen *ebiten.Image) error {
// // Update updates the audio stream by 1/60 [sec].
// if err := audioContext.Update(); err != nil {
// return err
// }
// // ...
// }
//
// func main() {
// audioContext, err = audio.NewContext(sampleRate)
// if err != nil {
// panic(err)
// }
// ebiten.Run(run, update, 320, 240, 2, "Audio test")
// }
//
// This is 'sync mode' in that game's (logical) time and audio time are synchronized.
// You can also call Update independently from the game loop as 'async mode'.
// In this case, audio goes on even when the game stops e.g. by diactivating the screen.
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type Context struct {
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players *players
driver *driver.Player
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sampleRate int
frames int
writtenBytes int
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}
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// NewContext creates a new audio context with the given sample rate (e.g. 44100).
func NewContext(sampleRate int) (*Context, error) {
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// TODO: Panic if one context exists.
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c := &Context{
sampleRate: sampleRate,
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}
c.players = &players{
players: map[*Player]struct{}{},
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}
// TODO: Rename this other than player
p, err := driver.NewPlayer(sampleRate, channelNum, bytesPerSample)
c.driver = p
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if err != nil {
return nil, err
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}
return c, nil
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}
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// Update proceeds the inner (logical) time of the context by 1/60 second.
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//
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// This is expected to be called in the game's updating function (sync mode)
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// or an independent goroutine with timers (async mode).
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// In sync mode, the game logical time syncs the audio logical time and
// you will find audio stops when the game stops e.g. when the window is deactivated.
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// In async mode, the audio never stops even when the game stops.
func (c *Context) Update() error {
c.frames++
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bytesPerFrame := c.sampleRate * bytesPerSample * channelNum / ebiten.FPS
l := (c.frames * bytesPerFrame) - c.writtenBytes
l &= mask
c.writtenBytes += l
buf := make([]byte, l)
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n, err := io.ReadFull(c.players, buf)
if err != nil {
return err
}
if n != len(buf) {
return c.driver.Close()
}
err = c.driver.Proceed(buf)
if err == io.EOF {
return c.driver.Close()
}
if err != nil {
return err
}
return nil
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}
// SampleRate returns the sample rate.
// All audio source must have the same sample rate.
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//
// This function is concurrent-safe.
func (c *Context) SampleRate() int {
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return c.sampleRate
}
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// ReadSeekCloser is an io.ReadSeeker and io.Closer.
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type ReadSeekCloser interface {
io.ReadSeeker
io.Closer
}
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// Player is an audio player which has one stream.
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type Player struct {
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players *players
src ReadSeekCloser
buf []byte
sampleRate int
pos int64
volume float64
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}
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// NewPlayer creates a new player with the given stream.
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//
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// src's format must be linear PCM (16bits little endian, 2 channel stereo)
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// without a header (e.g. RIFF header).
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// The sample rate must be same as that of the audio context.
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//
// This function is concurrent-safe.
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func (c *Context) NewPlayer(src ReadSeekCloser) (*Player, error) {
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p := &Player{
players: c.players,
src: src,
sampleRate: c.sampleRate,
buf: []byte{},
volume: 1,
}
// Get the current position of the source.
pos, err := p.src.Seek(0, 1)
if err != nil {
return nil, err
}
p.pos = pos
runtime.SetFinalizer(p, (*Player).Close)
return p, nil
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}
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// Close closes the stream. Ths source stream passed by NewPlayer will also be closed.
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//
// This function is concurrent-safe.
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func (p *Player) Close() error {
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p.players.removePlayer(p)
runtime.SetFinalizer(p, nil)
return p.src.Close()
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}
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func (p *Player) readToBuffer(length int) error {
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bb := make([]byte, length)
n, err := p.src.Read(bb)
if 0 < n {
p.buf = append(p.buf, bb[:n]...)
}
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return err
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}
func (p *Player) bufferToInt16(lengthInBytes int) []int16 {
r := make([]int16, lengthInBytes/2)
for i := 0; i < lengthInBytes/2; i++ {
r[i] = int16(p.buf[2*i]) | (int16(p.buf[2*i+1]) << 8)
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r[i] = int16(float64(r[i]) * p.volume)
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}
return r
}
func (p *Player) proceed(length int) {
p.buf = p.buf[length:]
p.pos += int64(length)
}
func (p *Player) bufferLength() int {
return len(p.buf)
}
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// Play plays the stream.
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//
// This function is concurrent-safe.
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func (p *Player) Play() error {
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p.players.addPlayer(p)
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return nil
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}
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// IsPlaying returns boolean indicating whether the player is playing.
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//
// This function is concurrent-safe.
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func (p *Player) IsPlaying() bool {
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return p.players.hasPlayer(p)
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}
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// Rewind rewinds the current position to the start.
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//
// This function is concurrent-safe.
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func (p *Player) Rewind() error {
return p.Seek(0)
}
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// Seek seeks the position with the given offset.
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//
// This function is concurrent-safe.
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func (p *Player) Seek(offset time.Duration) error {
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o := int64(offset) * bytesPerSample * channelNum * int64(p.sampleRate) / int64(time.Second)
o &= mask
return p.players.seekPlayer(p, o)
}
func (p *Player) seek(offset int64) error {
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p.buf = []byte{}
pos, err := p.src.Seek(offset, 0)
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if err != nil {
return err
}
p.pos = pos
return nil
}
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// Pause pauses the playing.
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//
// This function is concurrent-safe.
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func (p *Player) Pause() error {
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p.players.removePlayer(p)
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return nil
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}
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// Current returns the current position.
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//
// This function is concurrent-safe.
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func (p *Player) Current() time.Duration {
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return p.players.playerCurrent(p, p.sampleRate)
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}
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// Volume returns the current volume of this player [0-1].
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func (p *Player) Volume() float64 {
return p.volume
}
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// SetVolume sets the volume of this player.
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// volume must be in between 0 and 1. This function panics otherwise.
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func (p *Player) SetVolume(volume float64) {
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// The condition must be true when volume is NaN.
if !(0 <= volume && volume <= 1) {
panic("audio: volume must be in between 0 and 1")
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}
p.volume = volume
}