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:
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//
// [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"
"github.com/hajimehoshi/ebiten/v2/audio/internal/convert"
"github.com/hajimehoshi/ebiten/v2/internal/hooks"
)
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const (
channelCount = 2
bitDepthInBytes = 2
bytesPerSample = bitDepthInBytes * channelCount
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)
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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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playerFactory *playerFactory
// inited represents whether the audio device is initialized and available or not.
// On Android, audio loop cannot be started unless JVM is accessible. After updating one frame, JVM should exist.
inited chan struct{}
initedOnce sync.Once
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sampleRate int
err error
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ready bool
readyOnce sync.Once
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players map[*playerImpl]struct{}
m sync.Mutex
semaphore chan struct{}
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}
var (
theContext *Context
theContextLock sync.Mutex
)
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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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//
// NewContext panics when an audio context is already created.
func NewContext(sampleRate int) *Context {
theContextLock.Lock()
defer theContextLock.Unlock()
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if theContext != nil {
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panic("audio: context is already created")
}
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c := &Context{
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sampleRate: sampleRate,
playerFactory: newPlayerFactory(sampleRate),
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players: map[*playerImpl]struct{}{},
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inited: make(chan struct{}),
semaphore: make(chan struct{}, 1),
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}
theContext = c
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h := getHook()
h.OnSuspendAudio(func() error {
c.semaphore <- struct{}{}
if err := c.playerFactory.suspend(); err != nil {
return err
}
return nil
})
h.OnResumeAudio(func() error {
<-c.semaphore
if err := c.playerFactory.resume(); err != nil {
return err
}
return nil
})
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h.AppendHookOnBeforeUpdate(func() error {
c.initedOnce.Do(func() {
close(c.inited)
})
var err error
theContextLock.Lock()
if theContext != nil {
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err = theContext.error()
}
theContextLock.Unlock()
if err != nil {
return err
}
if err := c.gcPlayers(); err != nil {
return err
}
return nil
})
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return c
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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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func (c *Context) setError(err error) {
// TODO: What if c.err already exists?
c.m.Lock()
c.err = err
c.m.Unlock()
}
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func (c *Context) error() error {
c.m.Lock()
defer c.m.Unlock()
if c.err != nil {
return c.err
}
return c.playerFactory.error()
}
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func (c *Context) setReady() {
c.m.Lock()
c.ready = true
c.m.Unlock()
}
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func (c *Context) addPlayer(p *playerImpl) {
c.m.Lock()
defer c.m.Unlock()
c.players[p] = struct{}{}
// Check the source duplication
srcs := map[io.Reader]struct{}{}
for p := range c.players {
if _, ok := srcs[p.source()]; ok {
c.err = errors.New("audio: a same source is used by multiple Player")
return
}
srcs[p.source()] = struct{}{}
}
}
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func (c *Context) removePlayer(p *playerImpl) {
c.m.Lock()
delete(c.players, p)
c.m.Unlock()
}
func (c *Context) gcPlayers() error {
c.m.Lock()
defer c.m.Unlock()
// Now reader players cannot call removePlayers from themselves in the current implementation.
// Underlying playering can be the pause state after fishing its playing,
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// but there is no way to notify this to players so far.
// Instead, let's check the states proactively every frame.
for p := range c.players {
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if err := p.Err(); err != nil {
return err
}
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if !p.IsPlaying() {
delete(c.players, p)
}
}
return nil
}
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// IsReady returns a boolean value indicating whether the audio is ready or not.
//
// On some browsers, user interaction like click or pressing keys is required to start audio.
func (c *Context) IsReady() bool {
c.m.Lock()
defer c.m.Unlock()
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r := c.ready
if r {
return r
}
if len(c.players) != 0 {
return r
}
c.readyOnce.Do(func() {
// Create another goroutine since (*Player).Play can lock the context's mutex.
// TODO: Is this needed for reader players?
go func() {
// The audio context is never ready unless there is a player. This is
// problematic when a user tries to play audio after the context is ready.
// Play a dummy player to avoid the blocking (#969).
// Use a long enough buffer so that writing doesn't finish immediately (#970).
p := NewPlayerFromBytes(c, make([]byte, bufferSize()*2))
p.Play()
}()
})
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return r
}
// SampleRate returns the sample rate.
func (c *Context) SampleRate() int {
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return c.sampleRate
}
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func (c *Context) acquireSemaphore() {
c.semaphore <- struct{}{}
}
func (c *Context) releaseSemaphore() {
<-c.semaphore
}
func (c *Context) waitUntilInited() {
<-c.inited
}
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// Player is an audio player which has one stream.
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//
// Even when all references to a Player object is gone,
// the object is not GCed until the player finishes playing.
// This means that if a Player plays an infinite stream,
// the object is never GCed unless Close is called.
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type Player struct {
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p *playerImpl
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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 (signed 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.
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//
// A Player doesn't close src even if src implements io.Closer.
// Closing the source is src owner's responsibility.
func (c *Context) NewPlayer(src io.Reader) (*Player, error) {
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pi, err := c.playerFactory.newPlayer(c, src)
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if err != nil {
return nil, err
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}
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p := &Player{pi}
runtime.SetFinalizer(p, (*Player).finalize)
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return p, nil
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}
// NewPlayer creates a new player with the given stream.
//
// Deprecated: as of v2.2. Use (*Context).NewPlayer instead.
func NewPlayer(context *Context, src io.Reader) (*Player, error) {
return context.NewPlayer(src)
}
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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.
func (c *Context) NewPlayerFromBytes(src []byte) *Player {
p, err := c.NewPlayer(bytes.NewReader(src))
if err != nil {
// Errors should never happen.
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panic(fmt.Sprintf("audio: %v at NewPlayerFromBytes", err))
}
return p
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}
// NewPlayerFromBytes creates a new player with the given bytes.
//
// Deprecated: as of v2.2. Use (*Context).NewPlayerFromBytes instead.
func NewPlayerFromBytes(context *Context, src []byte) *Player {
return context.NewPlayerFromBytes(src)
}
func (p *Player) finalize() {
runtime.SetFinalizer(p, nil)
if !p.IsPlaying() {
p.Close()
}
}
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// Close closes the stream.
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//
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// When Close is called, the stream owned by the player is NOT closed,
// even if the stream implements io.Closer.
//
// Close returns error when the player is already closed.
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func (p *Player) Close() error {
return p.p.Close()
}
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// Play plays the stream.
func (p *Player) Play() {
p.p.Play()
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}
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// IsPlaying returns boolean indicating whether the player is playing.
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func (p *Player) IsPlaying() bool {
return p.p.IsPlaying()
}
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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 {
return p.p.Rewind()
}
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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 {
return p.p.Seek(offset)
}
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// Pause pauses the playing.
func (p *Player) Pause() {
p.p.Pause()
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}
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// Current returns the current position in time.
//
// As long as the player continues to play, Current's returning value is increased monotonically,
// even though the source stream loops and its position goes back.
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func (p *Player) Current() time.Duration {
return p.p.Current()
}
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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.p.Volume()
}
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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) {
p.p.SetVolume(volume)
}
// SetBufferSize adjusts the buffer size of the player.
// If 0 is specified, the default buffer size is used.
// A small buffer size is useful if you want to play a real-time PCM for example.
// Note that the audio quality might be affected if you modify the buffer size.
func (p *Player) SetBufferSize(bufferSize time.Duration) {
p.p.SetBufferSize(bufferSize)
}
type hook interface {
OnSuspendAudio(f func() error)
OnResumeAudio(f func() error)
AppendHookOnBeforeUpdate(f func() error)
}
var hookForTesting hook
func getHook() hook {
if hookForTesting != nil {
return hookForTesting
}
return &hookImpl{}
}
type hookImpl struct{}
func (h *hookImpl) OnSuspendAudio(f func() error) {
hooks.OnSuspendAudio(f)
}
func (h *hookImpl) OnResumeAudio(f func() error) {
hooks.OnResumeAudio(f)
}
func (h *hookImpl) AppendHookOnBeforeUpdate(f func() error) {
hooks.AppendHookOnBeforeUpdate(f)
}
// Resample converts the sample rate of the given stream.
// size is the length of the source stream in bytes.
// from is the original sample rate.
// to is the target sample rate.
//
// If the original sample rate equals to the new one, Resample returns source as it is.
func Resample(source io.ReadSeeker, size int64, from, to int) io.ReadSeeker {
if from == to {
return source
}
return convert.NewResampling(source, size, from, to)
}