ebiten/exp/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
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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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)
type mixingStream struct {
sampleRate int
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writtenBytes int
frames int
players map[*Player]struct{}
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// Note that Read (and other methods) need to be concurrent safe
// because Read is called from another groutine (see NewContext).
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sync.RWMutex
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}
func min(a, b int) int {
if a < b {
return a
}
return b
}
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const (
channelNum = 2
bytesPerSample = 2
bitsPerSample = bytesPerSample * 8
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// TODO: This assumes that channelNum is a power of 2.
mask = ^(channelNum*bytesPerSample - 1)
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)
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func (s *mixingStream) SampleRate() int {
s.RLock()
defer s.RUnlock()
return s.sampleRate
}
func (s *mixingStream) Read(b []byte) (int, error) {
s.Lock()
defer s.Unlock()
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bytesPerFrame := s.sampleRate * bytesPerSample * channelNum / ebiten.FPS
x := s.frames*bytesPerFrame + len(b)
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if x <= s.writtenBytes {
return 0, nil
}
if len(s.players) == 0 {
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l := min(len(b), x-s.writtenBytes)
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l &= mask
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copy(b, make([]byte, l))
s.writtenBytes += l
return l, nil
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}
closed := []*Player{}
l := len(b)
for p := range s.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{}
for p := range s.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)
}
for p := range s.players {
p.proceed(l)
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}
for _, p := range closed {
delete(s.players, p)
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}
s.writtenBytes += l
return l, nil
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}
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func (s *mixingStream) update() error {
s.Lock()
defer s.Unlock()
s.frames++
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return nil
}
func (s *mixingStream) newPlayer(src ReadSeekCloser) (*Player, error) {
s.Lock()
defer s.Unlock()
p := &Player{
stream: s,
src: src,
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
}
func (s *mixingStream) closePlayer(player *Player) error {
s.Lock()
defer s.Unlock()
runtime.SetFinalizer(player, nil)
return player.src.Close()
}
func (s *mixingStream) addPlayer(player *Player) {
s.Lock()
defer s.Unlock()
s.players[player] = struct{}{}
}
func (s *mixingStream) removePlayer(player *Player) {
s.Lock()
defer s.Unlock()
delete(s.players, player)
}
func (s *mixingStream) hasPlayer(player *Player) bool {
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s.RLock()
defer s.RUnlock()
_, ok := s.players[player]
return ok
}
func (s *mixingStream) seekPlayer(player *Player, offset time.Duration) error {
s.Lock()
defer s.Unlock()
o := int64(offset) * bytesPerSample * channelNum * int64(s.sampleRate) / int64(time.Second)
o &= mask
return player.seek(o)
}
func (s *mixingStream) playerCurrent(player *Player) time.Duration {
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s.RLock()
defer s.RUnlock()
sample := player.pos / bytesPerSample / channelNum
return time.Duration(sample) * time.Second / time.Duration(s.sampleRate)
}
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// TODO: Enable to specify the format like Mono8?
type Context struct {
stream *mixingStream
errorCh chan error
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}
func NewContext(sampleRate int) (*Context, error) {
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// TODO: Panic if one context exists.
c := &Context{
errorCh: make(chan error),
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}
c.stream = &mixingStream{
sampleRate: sampleRate,
players: map[*Player]struct{}{},
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}
// TODO: Rename this other than player
p, err := newPlayer(c.stream, sampleRate)
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if err != nil {
return nil, err
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}
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go func() {
// TODO: Is it OK to close asap?
defer p.close()
for {
err := p.proceed()
if err == io.EOF {
break
}
if err != nil {
c.errorCh <- err
return
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}
time.Sleep(1 * time.Millisecond)
}
}()
return c, nil
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}
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// Update proceeds the inner (logical) time of the context by 1/60 second.
// This is expected to be called in the game's updating function (sync mode)
// or an independent goroutine with timers (unsync mode).
// 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.
// In unsync mode, the audio never stops even when the game stops.
func (c *Context) Update() error {
select {
case err := <-c.errorCh:
return err
default:
}
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return c.stream.update()
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}
// SampleRate returns the sample rate.
// All audio source must have the same sample rate.
func (c *Context) SampleRate() int {
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return c.stream.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 {
stream *mixingStream
src ReadSeekCloser
buf []byte
pos int64
volume float64
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}
// NewPlayer creates a new player with the given data to the given channel.
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// The given data is queued to the end of the buffer.
// This may not be played immediately when data already exists in the buffer.
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//
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// src's format must be linear PCM (16bits, 2 channel stereo, little endian)
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// without a header (e.g. RIFF header).
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func (c *Context) NewPlayer(src ReadSeekCloser) (*Player, error) {
return c.stream.newPlayer(src)
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}
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func (p *Player) Close() error {
return p.stream.closePlayer(p)
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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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func (p *Player) Play() error {
p.stream.addPlayer(p)
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return nil
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}
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func (p *Player) IsPlaying() bool {
return p.stream.hasPlayer(p)
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}
func (p *Player) Rewind() error {
return p.Seek(0)
}
func (p *Player) Seek(offset time.Duration) error {
return p.stream.seekPlayer(p, offset)
}
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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func (p *Player) Pause() error {
p.stream.removePlayer(p)
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return nil
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}
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func (p *Player) Current() time.Duration {
return p.stream.playerCurrent(p)
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}
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func (p *Player) Volume() float64 {
return p.volume
}
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// SetVolume sets the volume.
// 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
}
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// TODO: Panning