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.
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//
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// The stream format must be 16-bit little endian and 2 channels. The format is as follows:
// [data] = [sample 1] [sample 2] [sample 3] ...
// [sample *] = [channel 1] ...
// [channel *] = [byte 1] [byte 2] ...
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//
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// An audio context (audio.Context object) has a sample rate you can specify and all streams you want to play must have the same
// sample rate. However, decoders in e.g. audio/mp3 package adjust sample rate automatically,
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// and you don't have to care about it as long as you use those decoders.
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//
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// An audio context can generate 'players' (audio.Player objects),
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// 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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//
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// For the simplest example to play sound, see wav package in the examples.
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package audio
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import (
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"bytes"
"errors"
"fmt"
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"io"
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"runtime"
"sync"
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"time"
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"github.com/hajimehoshi/oto"
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"github.com/hajimehoshi/ebiten/internal/clock"
"github.com/hajimehoshi/ebiten/internal/hooks"
"github.com/hajimehoshi/ebiten/internal/web"
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)
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type players struct {
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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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)
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func (p *players) Read(b []byte) (int, error) {
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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))
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return l, nil
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}
l := len(b)
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l &= mask
for player := range p.players {
if player.shouldSkip() {
continue
}
s := player.bufferSizeInBytes()
if l > s {
l = s
l &= mask
}
}
if l == 0 {
// If l is 0, all the players might reach EOF at the next update.
// However, this Read might block forever and never causes context switch
// on single-thread environment (e.g. browser).
// Call Gosched to cause context switch on purpose.
runtime.Gosched()
}
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b16s := [][]int16{}
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for player := range p.players {
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buf, err := player.bufferToInt16(l)
if err != nil {
return 0, err
}
b16s = append(b16s, buf)
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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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closed := []*Player{}
for player := range p.players {
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if player.eof() {
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closed = append(closed, player)
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}
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}
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for _, player := range closed {
delete(p.players, player)
}
return l, nil
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}
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func (p *players) addPlayer(player *Player) {
p.Lock()
p.players[player] = struct{}{}
p.Unlock()
}
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func (p *players) removePlayer(player *Player) {
p.Lock()
delete(p.players, player)
p.Unlock()
}
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func (p *players) hasPlayer(player *Player) bool {
p.RLock()
_, ok := p.players[player]
p.RUnlock()
return ok
}
func (p *players) hasSource(src io.ReadCloser) bool {
p.RLock()
defer p.RUnlock()
for player := range p.players {
if player.src == src {
return true
}
}
return false
}
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// A Context represents a current state of audio.
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//
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// At most one Context object can exist in one process.
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// This means only one constant sample rate is valid in your one application.
//
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// For a typical usage example, see examples/wav/main.go.
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type Context struct {
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players *players
sampleRate int
err error
m sync.Mutex
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}
var (
theContext *Context
theContextLock sync.Mutex
)
func init() {
hooks.AppendHookOnBeforeUpdate(func() error {
var err error
theContextLock.Lock()
if theContext != nil {
theContext.m.Lock()
err = theContext.err
theContext.m.Unlock()
}
theContextLock.Unlock()
return err
})
}
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// NewContext creates a new audio context with the given sample rate.
//
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// The sample rate is also used for decoding MP3 with audio/mp3 package
// or other formats as the target sample rate.
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//
// sampleRate should be 44100 or 48000.
// Other values might not work.
// For example, 22050 causes error on Safari when decoding MP3.
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//
// Error returned by NewContext is always nil as of 1.5.0-alpha.
//
// NewContext panics when an audio context is already created.
func NewContext(sampleRate int) (*Context, error) {
theContextLock.Lock()
defer theContextLock.Unlock()
if theContext != nil {
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panic("audio: context is already created")
}
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c := &Context{
sampleRate: sampleRate,
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}
theContext = c
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c.players = &players{
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players: map[*Player]struct{}{},
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}
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go c.loop()
return c, nil
}
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// CurrentContext returns the current context or nil if there is no context.
func CurrentContext() *Context {
theContextLock.Lock()
c := theContext
theContextLock.Unlock()
return c
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}
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func (c *Context) loop() {
initCh := make(chan struct{})
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suspendCh := make(chan struct{}, 1)
resumeCh := make(chan struct{}, 1)
hooks.OnSuspendAudio(func() {
suspendCh <- struct{}{}
})
hooks.OnResumeAudio(func() {
resumeCh <- struct{}{}
})
clock.OnStart(func() {
close(initCh)
})
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// Initialize oto.Player lazily to enable calling NewContext in an 'init' function.
// Accessing oto.Player functions requires the environment to be already initialized,
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// but if Ebiten is used for a shared library, the timing when init functions are called
// is unexpectable.
// e.g. a variable for JVM on Android might not be set.
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<-initCh
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p, err := oto.NewPlayer(c.sampleRate, channelNum, bytesPerSample, bufferSize())
if err != nil {
c.err = err
return
}
defer p.Close()
for {
select {
case <-suspendCh:
<-resumeCh
default:
const n = 2048
if _, err := io.CopyN(p, c.players, n); err != nil {
c.err = err
return
}
}
}
}
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// Update is deprecated as of 1.6.0-alpha.
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//
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// As of 1.6.0-alpha, Update always returns nil and does nothing related to updating the state.
// You don't have to call Update any longer.
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// The internal audio error is returned at ebiten.Run instead.
func (c *Context) Update() error {
return nil
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}
// SampleRate returns the sample rate.
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
}
type bytesReadSeekCloser struct {
reader *bytes.Reader
}
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func (b *bytesReadSeekCloser) Read(buf []byte) (int, error) {
return b.reader.Read(buf)
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}
func (b *bytesReadSeekCloser) Seek(offset int64, whence int) (int64, error) {
return b.reader.Seek(offset, whence)
}
func (b *bytesReadSeekCloser) Close() error {
b.reader = nil
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return nil
}
// BytesReadSeekCloser creates ReadSeekCloser from bytes.
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func BytesReadSeekCloser(b []byte) ReadSeekCloser {
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return &bytesReadSeekCloser{reader: bytes.NewReader(b)}
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}
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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 io.ReadCloser
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srcEOF bool
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sampleRate int
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buf []byte
pos int64
volume float64
closeCh chan struct{}
closedCh chan struct{}
readLoopEndedCh chan struct{}
seekCh chan seekArgs
seekedCh chan error
proceedCh chan []int16
proceededCh chan proceededValues
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syncCh chan func()
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}
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type seekArgs struct {
offset int64
whence int
}
type proceededValues struct {
buf []int16
err error
}
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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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//
// The player is seekable when src is io.Seeker.
// Attempt to seek the player that is not io.Seeker causes panic.
//
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// Note that the given src can't be shared with other Player objects.
//
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// NewPlayer tries to call Seek of src to get the current position.
// NewPlayer returns error when the Seek returns error.
func NewPlayer(context *Context, src io.ReadCloser) (*Player, error) {
if context.players.hasSource(src) {
return nil, errors.New("audio: src cannot be shared with another Player")
}
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p := &Player{
players: context.players,
src: src,
sampleRate: context.sampleRate,
buf: nil,
volume: 1,
closeCh: make(chan struct{}),
closedCh: make(chan struct{}),
readLoopEndedCh: make(chan struct{}),
seekCh: make(chan seekArgs),
seekedCh: make(chan error),
proceedCh: make(chan []int16),
proceededCh: make(chan proceededValues),
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syncCh: make(chan func()),
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}
if seeker, ok := p.src.(io.Seeker); ok {
// Get the current position of the source.
pos, err := seeker.Seek(0, io.SeekCurrent)
if err != nil {
return nil, err
}
p.pos = pos
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}
runtime.SetFinalizer(p, (*Player).Close)
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go func() {
p.readLoop()
}()
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return p, nil
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}
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// NewPlayerFromBytes creates a new player with the given bytes.
//
// As opposed to NewPlayer, you don't have to care if src is already used by another player or not.
// src can be shared by multiple players.
//
// The format of src should be same as noted at NewPlayer.
//
// NewPlayerFromBytes's error is always nil as of 1.5.0-alpha.
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func NewPlayerFromBytes(context *Context, src []byte) (*Player, error) {
b := BytesReadSeekCloser(src)
p, err := NewPlayer(context, b)
if err != nil {
// Errors should never happen.
panic(err)
}
return p, nil
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}
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// Close closes the stream.
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//
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// When closing, the stream owned by the player will also be closed by calling its Close.
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// This means that the source stream passed via NewPlayer will also be closed.
//
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// Close returns error when closing the source returns error.
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func (p *Player) Close() error {
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runtime.SetFinalizer(p, nil)
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p.players.removePlayer(p)
select {
case p.closeCh <- struct{}{}:
<-p.closedCh
return nil
case <-p.readLoopEndedCh:
return fmt.Errorf("audio: the player is already closed")
}
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}
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func (p *Player) bufferToInt16(lengthInBytes int) ([]int16, error) {
select {
case p.proceedCh <- make([]int16, lengthInBytes/2):
r := <-p.proceededCh
return r.buf, r.err
case <-p.readLoopEndedCh:
return nil, fmt.Errorf("audio: the player is already closed")
}
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}
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// Play plays the stream.
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//
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// Play always returns nil.
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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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func (p *Player) readLoop() {
defer func() {
// Note: the error is ignored
p.src.Close()
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// Receiving from a closed channel returns quickly
// i.e. `case <-p.readLoopEndedCh:` can check if this loops is ended.
close(p.readLoopEndedCh)
}()
timer := time.NewTimer(0)
timerCh := timer.C
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var readErr error
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for {
select {
case <-p.closeCh:
p.closedCh <- struct{}{}
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return
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case s := <-p.seekCh:
seeker, ok := p.src.(io.Seeker)
if !ok {
panic("not reached")
}
pos, err := seeker.Seek(s.offset, s.whence)
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p.buf = nil
p.pos = pos
p.srcEOF = false
p.seekedCh <- err
if timer != nil {
timer.Stop()
}
timer = time.NewTimer(time.Millisecond)
timerCh = timer.C
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break
case <-timerCh:
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// If the buffer has 1 second, that's enough.
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if len(p.buf) >= p.sampleRate*bytesPerSample*channelNum {
if timer != nil {
timer.Stop()
}
timer = time.NewTimer(100 * time.Millisecond)
timerCh = timer.C
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break
}
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// Try to read the buffer for 1/60[s].
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s := 60
if web.IsAndroidChrome() {
s = 10
} else if web.IsBrowser() {
s = 20
}
l := p.sampleRate * bytesPerSample * channelNum / s
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l &= mask
buf := make([]byte, l)
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n, err := p.src.Read(buf)
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p.buf = append(p.buf, buf[:n]...)
if err == io.EOF {
p.srcEOF = true
}
if p.srcEOF && len(p.buf) == 0 {
if timer != nil {
timer.Stop()
}
timer = nil
timerCh = nil
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break
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}
if err != nil && err != io.EOF {
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readErr = err
if timer != nil {
timer.Stop()
}
timer = nil
timerCh = nil
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break
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}
if timer != nil {
timer.Stop()
}
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if web.IsBrowser() {
timer = time.NewTimer(10 * time.Millisecond)
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} else {
timer = time.NewTimer(time.Millisecond)
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}
timerCh = timer.C
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case buf := <-p.proceedCh:
if readErr != nil {
p.proceededCh <- proceededValues{buf, readErr}
return
}
if p.shouldSkipImpl() {
// Return zero values.
p.proceededCh <- proceededValues{buf, nil}
break
}
lengthInBytes := len(buf) * 2
l := lengthInBytes
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if l > len(p.buf) {
l = len(p.buf)
}
for i := 0; i < l/2; i++ {
buf[i] = int16(p.buf[2*i]) | (int16(p.buf[2*i+1]) << 8)
buf[i] = int16(float64(buf[i]) * p.volume)
}
p.pos += int64(l)
p.buf = p.buf[l:]
p.proceededCh <- proceededValues{buf[:l/2], nil}
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case f := <-p.syncCh:
f()
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}
}
}
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func (p *Player) sync(f func()) bool {
ch := make(chan struct{})
ff := func() {
f()
close(ch)
}
select {
case p.syncCh <- ff:
<-ch
return true
case <-p.readLoopEndedCh:
return false
}
}
func (p *Player) shouldSkip() bool {
r := false
p.sync(func() {
r = p.shouldSkipImpl()
})
return r
}
func (p *Player) shouldSkipImpl() bool {
// When p.buf is nil, the player just starts playing or seeking.
// Note that this is different from len(p.buf) == 0 && p.buf != nil.
if p.buf == nil {
return true
}
if p.eofImpl() {
return true
}
return false
}
func (p *Player) bufferSizeInBytes() int {
s := 0
p.sync(func() {
s = len(p.buf)
})
return s
}
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func (p *Player) eof() bool {
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r := false
p.sync(func() {
r = p.eofImpl()
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})
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return r
}
func (p *Player) eofImpl() bool {
return p.srcEOF && len(p.buf) == 0
}
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// IsPlaying returns boolean indicating whether the player is playing.
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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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//
// The passed source to NewPlayer must be io.Seeker, or Rewind panics.
//
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// Rewind returns error when seeking the source stream returns error.
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func (p *Player) Rewind() error {
if _, ok := p.src.(io.Seeker); !ok {
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panic("audio: player to be rewound must be io.Seeker")
}
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return p.Seek(0)
}
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// Seek seeks the position with the given offset.
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//
// The passed source to NewPlayer must be io.Seeker, or Seek panics.
//
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// Seek returns error when seeking the source stream returns error.
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func (p *Player) Seek(offset time.Duration) error {
if _, ok := p.src.(io.Seeker); !ok {
panic("audio: player to be sought must be io.Seeker")
}
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o := int64(offset) * bytesPerSample * channelNum * int64(p.sampleRate) / int64(time.Second)
o &= mask
select {
case p.seekCh <- seekArgs{o, io.SeekStart}:
return <-p.seekedCh
case <-p.readLoopEndedCh:
return fmt.Errorf("audio: the player is already closed")
}
}
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// Pause pauses the playing.
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//
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// Pause always returns nil.
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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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func (p *Player) Current() time.Duration {
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sample := int64(0)
p.sync(func() {
sample = p.pos / bytesPerSample / channelNum
})
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return time.Duration(sample) * time.Second / time.Duration(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 {
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v := 0.0
p.sync(func() {
v = p.volume
})
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return v
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}
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// SetVolume sets the volume of this player.
// volume must be in between 0 and 1. SetVolume 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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}
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p.sync(func() {
p.volume = volume
})
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}