ebiten/audio/player.go

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// Copyright 2021 The Ebiten Authors
//
// 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
import (
"io"
"runtime"
"sync"
"time"
)
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// player is almost the same as the interface oto.Player.
// This is defined in order to remove the dependency on Oto from this file.
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type player interface {
Pause()
Play()
IsPlaying() bool
Volume() float64
SetVolume(volume float64)
UnplayedBufferSize() int
Err() error
SetBufferSize(bufferSize int)
io.Seeker
io.Closer
}
type context interface {
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NewPlayer(io.Reader) player
Suspend() error
Resume() error
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Err() error
}
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type playerFactory struct {
context context
sampleRate int
m sync.Mutex
}
var driverForTesting context
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func newPlayerFactory(sampleRate int) *playerFactory {
f := &playerFactory{
sampleRate: sampleRate,
}
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if driverForTesting != nil {
f.context = driverForTesting
}
// TODO: Consider the hooks.
return f
}
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type playerImpl struct {
context *Context
player player
src io.Reader
stream *timeStream
factory *playerFactory
initBufferSize int
m sync.Mutex
}
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func (f *playerFactory) newPlayer(context *Context, src io.Reader) (*playerImpl, error) {
f.m.Lock()
defer f.m.Unlock()
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p := &playerImpl{
src: src,
context: context,
factory: f,
}
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runtime.SetFinalizer(p, (*playerImpl).Close)
return p, nil
}
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func (f *playerFactory) suspend() error {
f.m.Lock()
defer f.m.Unlock()
if f.context == nil {
return nil
}
return f.context.Suspend()
}
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func (f *playerFactory) resume() error {
f.m.Lock()
defer f.m.Unlock()
if f.context == nil {
return nil
}
return f.context.Resume()
}
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func (f *playerFactory) error() error {
f.m.Lock()
defer f.m.Unlock()
if f.context == nil {
return nil
}
return f.context.Err()
}
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func (f *playerFactory) initContextIfNeeded() (<-chan struct{}, error) {
f.m.Lock()
defer f.m.Unlock()
if f.context != nil {
return nil, nil
}
c, ready, err := newContext(f.sampleRate)
if err != nil {
return nil, err
}
f.context = c
return ready, nil
}
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func (p *playerImpl) ensurePlayer() error {
// Initialize the underlying player lazily to enable calling NewContext in an 'init' function.
// Accessing the underlying player functions requires the environment to be already initialized,
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// but if Ebitengine 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.
ready, err := p.factory.initContextIfNeeded()
if err != nil {
return err
}
if ready != nil {
go func() {
<-ready
p.context.setReady()
}()
}
if p.stream == nil {
s, err := newTimeStream(p.src, p.factory.sampleRate)
if err != nil {
return err
}
p.stream = s
}
if p.player == nil {
p.player = p.factory.context.NewPlayer(p.stream)
if p.initBufferSize != 0 {
p.player.SetBufferSize(p.initBufferSize)
p.initBufferSize = 0
}
}
return nil
}
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func (p *playerImpl) Play() {
p.m.Lock()
defer p.m.Unlock()
if err := p.ensurePlayer(); err != nil {
p.context.setError(err)
return
}
if p.player.IsPlaying() {
return
}
p.player.Play()
p.context.addPlayer(p)
}
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func (p *playerImpl) Pause() {
p.m.Lock()
defer p.m.Unlock()
if p.player == nil {
return
}
if !p.player.IsPlaying() {
return
}
p.player.Pause()
p.context.removePlayer(p)
}
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func (p *playerImpl) IsPlaying() bool {
p.m.Lock()
defer p.m.Unlock()
if p.player == nil {
return false
}
return p.player.IsPlaying()
}
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func (p *playerImpl) Volume() float64 {
p.m.Lock()
defer p.m.Unlock()
if err := p.ensurePlayer(); err != nil {
p.context.setError(err)
return 0
}
return p.player.Volume()
}
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func (p *playerImpl) SetVolume(volume float64) {
p.m.Lock()
defer p.m.Unlock()
if err := p.ensurePlayer(); err != nil {
p.context.setError(err)
return
}
p.player.SetVolume(volume)
}
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func (p *playerImpl) Close() error {
p.m.Lock()
defer p.m.Unlock()
runtime.SetFinalizer(p, nil)
if p.player != nil {
defer func() {
p.player = nil
}()
p.player.Pause()
return p.player.Close()
}
return nil
}
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func (p *playerImpl) Current() time.Duration {
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p.m.Lock()
defer p.m.Unlock()
if err := p.ensurePlayer(); err != nil {
p.context.setError(err)
return 0
}
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samples := (p.stream.Current() - int64(p.player.UnplayedBufferSize())) / bytesPerSample
return time.Duration(samples) * time.Second / time.Duration(p.factory.sampleRate)
}
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func (p *playerImpl) Rewind() error {
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return p.Seek(0)
}
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func (p *playerImpl) Seek(offset time.Duration) error {
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p.m.Lock()
defer p.m.Unlock()
if err := p.ensurePlayer(); err != nil {
return err
}
pos := p.stream.timeDurationToPos(offset)
if _, err := p.player.Seek(pos, io.SeekStart); err != nil {
return err
}
return nil
}
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func (p *playerImpl) Err() error {
p.m.Lock()
defer p.m.Unlock()
if p.player == nil {
return nil
}
return p.player.Err()
}
func (p *playerImpl) SetBufferSize(bufferSize time.Duration) {
p.m.Lock()
defer p.m.Unlock()
bufferSizeInBytes := int(bufferSize * bytesPerSample * time.Duration(p.factory.sampleRate) / time.Second)
bufferSizeInBytes = bufferSizeInBytes / bytesPerSample * bytesPerSample
if p.player == nil {
p.initBufferSize = bufferSizeInBytes
return
}
p.player.SetBufferSize(bufferSizeInBytes)
}
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func (p *playerImpl) source() io.Reader {
return p.src
}
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type timeStream struct {
r io.Reader
sampleRate int
pos int64
// m is a mutex for this stream.
// All the exported functions are protected by this mutex as Read can be read from a different goroutine than Seek.
m sync.Mutex
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}
func newTimeStream(r io.Reader, sampleRate int) (*timeStream, error) {
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s := &timeStream{
r: r,
sampleRate: sampleRate,
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}
if seeker, ok := s.r.(io.Seeker); ok {
// Get the current position of the source.
pos, err := seeker.Seek(0, io.SeekCurrent)
if err != nil {
return nil, err
}
s.pos = pos
}
return s, nil
}
func (s *timeStream) Read(buf []byte) (int, error) {
s.m.Lock()
defer s.m.Unlock()
n, err := s.r.Read(buf)
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s.pos += int64(n)
return n, err
}
func (s *timeStream) Seek(offset int64, whence int) (int64, error) {
s.m.Lock()
defer s.m.Unlock()
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seeker, ok := s.r.(io.Seeker)
if !ok {
// TODO: Should this return an error?
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panic("audio: the source must be io.Seeker when seeking but not")
}
pos, err := seeker.Seek(offset, whence)
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if err != nil {
return pos, err
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}
s.pos = pos
return pos, nil
}
func (s *timeStream) timeDurationToPos(offset time.Duration) int64 {
s.m.Lock()
defer s.m.Unlock()
o := int64(offset) * bytesPerSample * int64(s.sampleRate) / int64(time.Second)
// Align the byte position with the samples.
o -= o % bytesPerSample
o += s.pos % bytesPerSample
return o
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}
func (s *timeStream) Current() int64 {
s.m.Lock()
defer s.m.Unlock()
return s.pos
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}