ebiten/audio/audio.go
Hajime Hoshi 273093b237 audio: Skip the player in the state of starting, seeking or EOF
This is basically reland of
2fee7a6fe5.

Before this change, if a player's buffer was not enough for
reading, 0 value were used and this caused noises. The reading
size should be aligned with all the players.

However, there are some cases that the player should be skippped.
For example, just after a player just starts playing or seeking,
the buffer is empty. In this case, other players should not wait
for the player since decoding might take some time. Another case
is that the player reached EOF.

This change aligns the read buffer sizes but use zero values only
when the player just starts or seeks, or reaches EOF.
2018-06-09 22:00:11 +09:00

705 lines
16 KiB
Go

// 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 audio provides audio players.
//
// 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] ...
//
// 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,
// and you don't have to care about it as long as you use those decoders.
//
// An audio context can generate 'players' (audio.Player objects),
// 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.
//
// For the simplest example to play sound, see wav package in the examples.
package audio
import (
"bytes"
"errors"
"fmt"
"io"
"runtime"
"sync"
"time"
"github.com/hajimehoshi/oto"
"github.com/hajimehoshi/ebiten/internal/clock"
"github.com/hajimehoshi/ebiten/internal/hooks"
"github.com/hajimehoshi/ebiten/internal/web"
)
type players struct {
players map[*Player]struct{}
sync.RWMutex
}
const (
channelNum = 2
bytesPerSample = 2
// TODO: This assumes that channelNum is a power of 2.
mask = ^(channelNum*bytesPerSample - 1)
)
func (p *players) Read(b []byte) (int, error) {
p.Lock()
defer p.Unlock()
if len(p.players) == 0 {
l := len(b)
l &= mask
copy(b, make([]byte, l))
return l, nil
}
l := len(b)
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()
}
b16s := [][]int16{}
for player := range p.players {
buf, err := player.bufferToInt16(l)
if err != nil {
return 0, err
}
b16s = append(b16s, buf)
}
for i := 0; i < l/2; i++ {
x := 0
for _, b16 := range b16s {
x += int(b16[i])
}
if x > (1<<15)-1 {
x = (1 << 15) - 1
}
if x < -(1 << 15) {
x = -(1 << 15)
}
b[2*i] = byte(x)
b[2*i+1] = byte(x >> 8)
}
closed := []*Player{}
for player := range p.players {
if player.eof() {
closed = append(closed, player)
}
}
for _, player := range closed {
delete(p.players, player)
}
return l, nil
}
func (p *players) addPlayer(player *Player) {
p.Lock()
p.players[player] = struct{}{}
p.Unlock()
}
func (p *players) removePlayer(player *Player) {
p.Lock()
delete(p.players, player)
p.Unlock()
}
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
}
// A Context represents a current state of audio.
//
// At most one Context object can exist in one process.
// This means only one constant sample rate is valid in your one application.
//
// For a typical usage example, see examples/wav/main.go.
type Context struct {
players *players
sampleRate int
err error
m sync.Mutex
}
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
})
}
// NewContext creates a new audio context with the given sample rate.
//
// The sample rate is also used for decoding MP3 with audio/mp3 package
// or other formats as the target sample rate.
//
// sampleRate should be 44100 or 48000.
// Other values might not work.
// For example, 22050 causes error on Safari when decoding MP3.
//
// 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 {
panic("audio: context is already created")
}
c := &Context{
sampleRate: sampleRate,
}
theContext = c
c.players = &players{
players: map[*Player]struct{}{},
}
go c.loop()
return c, nil
}
// CurrentContext returns the current context or nil if there is no context.
func CurrentContext() *Context {
theContextLock.Lock()
c := theContext
theContextLock.Unlock()
return c
}
func (c *Context) loop() {
initCh := make(chan struct{})
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)
})
// Initialize oto.Player lazily to enable calling NewContext in an 'init' function.
// Accessing oto.Player functions requires the environment to be already initialized,
// 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.
<-initCh
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
}
}
}
}
// Update is deprecated as of 1.6.0-alpha.
//
// As of 1.6.0-alpha, Update always returns nil and does nothing related to updating the state.
// You don't have to call this function any longer.
// The internal audio error is returned at ebiten.Run instead.
func (c *Context) Update() error {
return nil
}
// SampleRate returns the sample rate.
func (c *Context) SampleRate() int {
return c.sampleRate
}
// ReadSeekCloser is an io.ReadSeeker and io.Closer.
type ReadSeekCloser interface {
io.ReadSeeker
io.Closer
}
type bytesReadSeekCloser struct {
reader *bytes.Reader
}
func (b *bytesReadSeekCloser) Read(buf []byte) (int, error) {
return b.reader.Read(buf)
}
func (b *bytesReadSeekCloser) Seek(offset int64, whence int) (int64, error) {
return b.reader.Seek(offset, whence)
}
func (b *bytesReadSeekCloser) Close() error {
b.reader = nil
return nil
}
// BytesReadSeekCloser creates ReadSeekCloser from bytes.
func BytesReadSeekCloser(b []byte) ReadSeekCloser {
return &bytesReadSeekCloser{reader: bytes.NewReader(b)}
}
// Player is an audio player which has one stream.
type Player struct {
players *players
src io.ReadCloser
srcEOF bool
sampleRate int
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
syncCh chan func()
}
type seekArgs struct {
offset int64
whence int
}
type proceededValues struct {
buf []int16
err error
}
// NewPlayer creates a new player with the given stream.
//
// src's format must be linear PCM (16bits little endian, 2 channel stereo)
// without a header (e.g. RIFF header).
// The sample rate must be same as that of the audio context.
//
// The player is seekable when src is io.Seeker.
// Attempt to seek the player that is not io.Seeker causes panic.
//
// Note that the given src can't be shared with other Player objects.
//
// 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")
}
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),
syncCh: make(chan func()),
}
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
}
runtime.SetFinalizer(p, (*Player).Close)
go func() {
p.readLoop()
}()
return p, nil
}
// 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.
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
}
// Close closes the stream.
//
// When closing, the stream owned by the player will also be closed by calling its Close.
// This means that the source stream passed via NewPlayer will also be closed.
//
// Close returns error when closing the source returns error.
func (p *Player) Close() error {
runtime.SetFinalizer(p, nil)
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")
}
}
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")
}
}
// Play plays the stream.
//
// Play always returns nil.
func (p *Player) Play() error {
p.players.addPlayer(p)
return nil
}
func (p *Player) readLoop() {
defer func() {
// Note: the error is ignored
p.src.Close()
// 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
var readErr error
for {
select {
case <-p.closeCh:
p.closedCh <- struct{}{}
return
case s := <-p.seekCh:
seeker, ok := p.src.(io.Seeker)
if !ok {
panic("not reached")
}
pos, err := seeker.Seek(s.offset, s.whence)
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
break
case <-timerCh:
// If the buffer has 1 second, that's enough.
if len(p.buf) >= p.sampleRate*bytesPerSample*channelNum {
if timer != nil {
timer.Stop()
}
timer = time.NewTimer(100 * time.Millisecond)
timerCh = timer.C
break
}
// Try to read the buffer for 1/60[s].
s := 60
if web.IsAndroidChrome() {
s = 10
} else if web.IsBrowser() {
s = 20
}
l := p.sampleRate * bytesPerSample * channelNum / s
l &= mask
buf := make([]byte, l)
n, err := p.src.Read(buf)
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
break
}
if err != nil && err != io.EOF {
readErr = err
if timer != nil {
timer.Stop()
}
timer = nil
timerCh = nil
break
}
if timer != nil {
timer.Stop()
}
if web.IsBrowser() {
timer = time.NewTimer(10 * time.Millisecond)
} else {
timer = time.NewTimer(time.Millisecond)
}
timerCh = timer.C
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
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}
case f := <-p.syncCh:
f()
}
}
}
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
}
func (p *Player) eof() bool {
r := false
p.sync(func() {
r = p.eofImpl()
})
return r
}
func (p *Player) eofImpl() bool {
return p.srcEOF && len(p.buf) == 0
}
// IsPlaying returns boolean indicating whether the player is playing.
func (p *Player) IsPlaying() bool {
return p.players.hasPlayer(p)
}
// Rewind rewinds the current position to the start.
//
// The passed source to NewPlayer must be io.Seeker, or Rewind panics.
//
// Rewind returns error when seeking the source stream returns error.
func (p *Player) Rewind() error {
if _, ok := p.src.(io.Seeker); !ok {
panic("audio: player to be rewound must be io.Seeker")
}
return p.Seek(0)
}
// Seek seeks the position with the given offset.
//
// The passed source to NewPlayer must be io.Seeker, or Seek panics.
//
// Seek returns error when seeking the source stream returns error.
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")
}
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")
}
}
// Pause pauses the playing.
//
// Pause always returns nil.
func (p *Player) Pause() error {
p.players.removePlayer(p)
return nil
}
// Current returns the current position.
func (p *Player) Current() time.Duration {
sample := int64(0)
p.sync(func() {
sample = p.pos / bytesPerSample / channelNum
})
return time.Duration(sample) * time.Second / time.Duration(p.sampleRate)
}
// Volume returns the current volume of this player [0-1].
func (p *Player) Volume() float64 {
v := 0.0
p.sync(func() {
v = p.volume
})
return v
}
// SetVolume sets the volume of this player.
// volume must be in between 0 and 1. This function panics otherwise.
func (p *Player) SetVolume(volume float64) {
// The condition must be true when volume is NaN.
if !(0 <= volume && volume <= 1) {
panic("audio: volume must be in between 0 and 1")
}
p.sync(func() {
p.volume = volume
})
}