audio/internal/readerdriver: Do mixing on Ebiten side

Creating a new AudioQueue is more expensive than expected, and
this caused a little blocking the game when playing a lot of SEs.

Closes #1702
Updates #1680

audio/internal/readerdriver/driver_darwin.go

@@ -25,8 +25,6 @@ import "C"
 
 import (
 	"fmt"
-	"io"
-	"runtime"
 	"sync"
 	"time"
 	"unsafe"
@@ -36,56 +34,20 @@ func IsAvailable() bool {
 	return true
 }
 
-type audioQueuePoolItem struct {
+const (
-	queue C.AudioQueueRef
+	float32SizeInBytes = 4
-	bufs  []C.AudioQueueBufferRef
+)
-}
 
-const audioQueuePoolMaxItemNum = 32 // 32 is an arbitrary number.
+func newAudioQueue(sampleRate, channelNum, bitDepthInBytes int) (C.AudioQueueRef, []C.AudioQueueBufferRef, error) {
-
-type audioQueuePool struct {
-	c      *context
-	unused []audioQueuePoolItem
-	used   []audioQueuePoolItem
-	m      sync.Mutex
-}
-
-func (a *audioQueuePool) Prepare(context *context) error {
-	a.c = context
-	for i := 0; i < audioQueuePoolMaxItemNum; i++ {
-		if _, _, err := a.Get(); err != nil {
-			return err
-		}
-	}
-	a.unused = a.used
-	a.used = a.used[:0]
-	return nil
-}
-
-func (a *audioQueuePool) Get() (C.AudioQueueRef, []C.AudioQueueBufferRef, error) {
-	a.m.Lock()
-	defer a.m.Unlock()
-
-	if len(a.unused) > 0 {
-		q := a.unused[0]
-		a.unused = a.unused[1:]
-		a.used = append(a.used, q)
-		return q.queue, q.bufs, nil
-	}
-
-	flags := C.kAudioFormatFlagIsPacked
-	if a.c.bitDepthInBytes != 1 {
-		flags |= C.kAudioFormatFlagIsSignedInteger
-	}
 	desc := C.AudioStreamBasicDescription{
-		mSampleRate:       C.double(a.c.sampleRate),
+		mSampleRate:       C.double(sampleRate),
 		mFormatID:         C.kAudioFormatLinearPCM,
-		mFormatFlags:      C.UInt32(flags),
+		mFormatFlags:      C.kAudioFormatFlagIsFloat,
-		mBytesPerPacket:   C.UInt32(a.c.channelNum * a.c.bitDepthInBytes),
+		mBytesPerPacket:   C.UInt32(channelNum * float32SizeInBytes),
 		mFramesPerPacket:  1,
-		mBytesPerFrame:    C.UInt32(a.c.channelNum * a.c.bitDepthInBytes),
+		mBytesPerFrame:    C.UInt32(channelNum * float32SizeInBytes),
-		mChannelsPerFrame: C.UInt32(a.c.channelNum),
+		mChannelsPerFrame: C.UInt32(channelNum),
-		mBitsPerChannel:   C.UInt32(8 * a.c.bitDepthInBytes),
+		mBitsPerChannel:   C.UInt32(8 * float32SizeInBytes),
 	}
 
 	var audioQueue C.AudioQueueRef
@@ -100,65 +62,37 @@ func (a *audioQueuePool) Get() (C.AudioQueueRef, []C.AudioQueueBufferRef, error)
 		return nil, nil, fmt.Errorf("readerdriver: AudioQueueNewFormat with StreamFormat failed: %d", osstatus)
 	}
 
-	size := a.c.oneBufferSize()
+	bufs := make([]C.AudioQueueBufferRef, 0, 4)
-	bufs := make([]C.AudioQueueBufferRef, 0, 2)
 	for len(bufs) < cap(bufs) {
 		var buf C.AudioQueueBufferRef
-		if osstatus := C.AudioQueueAllocateBuffer(audioQueue, C.UInt32(size), &buf); osstatus != C.noErr {
+		if osstatus := C.AudioQueueAllocateBuffer(audioQueue, bufferSizeInBytes, &buf); osstatus != C.noErr {
 			return nil, nil, fmt.Errorf("readerdriver: AudioQueueAllocateBuffer failed: %d", osstatus)
 		}
-		buf.mAudioDataByteSize = C.UInt32(size)
+		buf.mAudioDataByteSize = bufferSizeInBytes
 		bufs = append(bufs, buf)
 	}
 
-	a.used = append(a.used, audioQueuePoolItem{
-		queue: audioQueue,
-		bufs:  bufs,
-	})
-
 	return audioQueue, bufs, nil
 }
 
-func (a *audioQueuePool) Put(audioQueue C.AudioQueueRef) error {
-	a.m.Lock()
-	defer a.m.Unlock()
-
-	for i, q := range a.used {
-		if q.queue != audioQueue {
-			continue
-		}
-
-		a.used = append(a.used[:i], a.used[i+1:]...)
-		if len(a.unused)+len(a.used) < audioQueuePoolMaxItemNum {
-			a.unused = append(a.unused, q)
-			break
-		}
-
-		// As the pool is too big, remove the AudioQueue.
-		for _, b := range q.bufs {
-			if osstatus := C.AudioQueueFreeBuffer(q.queue, b); osstatus != C.noErr {
-				return fmt.Errorf("readerdriver: AudioQueueFreeBuffer failed: %d", osstatus)
-			}
-		}
-		if osstatus := C.AudioQueueDispose(q.queue, C.true); osstatus != C.noErr {
-			return fmt.Errorf("readerdriver: AudioQueueDispose failed: %d", osstatus)
-		}
-		break
-	}
-	return nil
-}
-
 type context struct {
 	sampleRate      int
 	channelNum      int
 	bitDepthInBytes int
 
-	audioQueuePool audioQueuePool
+	audioQueue      C.AudioQueueRef
+	unqueuedBuffers []C.AudioQueueBufferRef
+
+	cond *sync.Cond
+
+	players *players
 }
 
 // TOOD: Convert the error code correctly.
 // See https://stackoverflow.com/questions/2196869/how-do-you-convert-an-iphone-osstatus-code-to-something-useful
 
+var theContext *context
+
 func NewContext(sampleRate, channelNum, bitDepthInBytes int) (Context, chan struct{}, error) {
 	ready := make(chan struct{})
 	close(ready)
@@ -167,564 +101,101 @@ func NewContext(sampleRate, channelNum, bitDepthInBytes int) (Context, chan stru
 		sampleRate:      sampleRate,
 		channelNum:      channelNum,
 		bitDepthInBytes: bitDepthInBytes,
+		cond:            sync.NewCond(&sync.Mutex{}),
+		players:         newPlayers(),
 	}
-	if err := c.audioQueuePool.Prepare(c); err != nil {
+	theContext = c
+
+	q, bs, err := newAudioQueue(sampleRate, channelNum, bitDepthInBytes)
+	if err != nil {
 		return nil, nil, err
 	}
+	c.audioQueue = q
+	c.unqueuedBuffers = bs
+
 	C.ebiten_readerdriver_setNotificationHandler()
+
+	if osstatus := C.AudioQueueStart(c.audioQueue, nil); osstatus != C.noErr {
+		return nil, nil, fmt.Errorf("readerdriver: AudioQueueStart failed: %d", osstatus)
+	}
+
+	go c.loop()
+
 	return c, ready, nil
 }
 
+func (c *context) wait() {
+	c.cond.L.Lock()
+	defer c.cond.L.Unlock()
+
+	for len(c.unqueuedBuffers) == 0 {
+		c.cond.Wait()
+	}
+}
+
+func (c *context) loop() {
+	buf32 := make([]float32, bufferSizeInBytes/4)
+	for {
+		c.wait()
+		c.appendBuffer(buf32)
+	}
+}
+
+func (c *context) appendBuffer(buf32 []float32) {
+	c.cond.L.Lock()
+	defer c.cond.L.Unlock()
+
+	buf := c.unqueuedBuffers[0]
+	c.unqueuedBuffers = c.unqueuedBuffers[1:]
+
+	for i := range buf32 {
+		buf32[i] = 0
+	}
+	c.players.read(buf32)
+	for i, f := range buf32 {
+		*(*float32)(unsafe.Pointer(uintptr(buf.mAudioData) + uintptr(i)*float32SizeInBytes)) = f
+	}
+
+	if osstatus := C.AudioQueueEnqueueBuffer(c.audioQueue, buf, 0, nil); osstatus != C.noErr {
+		// TODO: Treat the error correctly
+		panic(fmt.Errorf("readerdriver: AudioQueueEnqueueBuffer failed: %d", osstatus))
+	}
+}
+
 func (c *context) Suspend() error {
-	return thePlayers.suspend()
+	if osstatus := C.AudioQueuePause(c.audioQueue); osstatus != C.noErr {
+		return fmt.Errorf("readerdriver: AudioQueuePause failed: %d", osstatus)
+	}
+	return nil
 }
 
 func (c *context) Resume() error {
-	return thePlayers.resume()
+try:
-}
+	if osstatus := C.AudioQueueStart(c.audioQueue, nil); osstatus != C.noErr {
-
+		const AVAudioSessionErrorCodeSiriIsRecording = 0x73697269 // 'siri'
-type player struct {
+		if osstatus == AVAudioSessionErrorCodeSiriIsRecording {
-	p *playerImpl
-}
-
-type playerImpl struct {
-	context      *context
-	src          io.Reader
-	id           int
-	audioQueue   C.AudioQueueRef
-	buf          []byte
-	unqueuedBufs []C.AudioQueueBufferRef
-	state        playerState
-	err          error
-	eof          bool
-	volume       float64
-
-	m sync.Mutex
-}
-
-type players struct {
-	players  map[C.AudioQueueRef]*playerImpl
-	toResume map[*playerImpl]struct{}
-	cond     *sync.Cond
-}
-
-func (p *players) add(player *playerImpl, audioQueue C.AudioQueueRef) {
-	p.cond.L.Lock()
-	defer p.cond.L.Unlock()
-
-	if p.players == nil {
-		p.players = map[C.AudioQueueRef]*playerImpl{}
-	}
-	runLoop := len(p.players) == 0
-	p.players[audioQueue] = player
-	if runLoop {
-		// Use the only one loop for multiple players (#1662).
-		go p.loop()
-	}
-}
-
-func (p *players) get(audioQueue C.AudioQueueRef) *playerImpl {
-	p.cond.L.Lock()
-	defer p.cond.L.Unlock()
-	return p.players[audioQueue]
-}
-
-func (p *players) remove(audioQueue C.AudioQueueRef) {
-	p.cond.L.Lock()
-	defer p.cond.L.Unlock()
-
-	pl, ok := p.players[audioQueue]
-	if !ok {
-		return
-	}
-	delete(p.players, audioQueue)
-	delete(p.toResume, pl)
-
-	p.cond.Signal()
-}
-
-func (p *players) shouldWait() bool {
-	if len(p.players) == 0 {
-		return false
-	}
-
-	for _, pl := range p.players {
-		if pl.canReadSourceToBuffer() {
-			return false
-		}
-	}
-	return true
-}
-
-func (p *players) wait() bool {
-	p.cond.L.Lock()
-	defer p.cond.L.Unlock()
-
-	for p.shouldWait() {
-		p.cond.Wait()
-	}
-	return len(p.players) > 0
-}
-
-func (p *players) loop() {
-	var players []*playerImpl
-	for {
-		if !p.wait() {
-			return
-		}
-
-		p.cond.L.Lock()
-		players = players[:0]
-		for _, pl := range p.players {
-			players = append(players, pl)
-		}
-		p.cond.L.Unlock()
-
-		for _, pl := range players {
-			pl.readSourceToBuffer()
-		}
-	}
-}
-
-func (p *players) suspend() error {
-	p.cond.L.Lock()
-	defer p.cond.L.Unlock()
-
-	for _, pl := range p.players {
-		if !pl.IsPlaying() {
-			continue
-		}
-		// TODO: Is this OK to Pause instead of Close?
-		// Oboe (Android) closes players when suspending to avoid hogging audio resources which other apps could use.
-		pl.Pause()
-		if err := pl.Err(); err != nil {
-			return err
-		}
-		if p.toResume == nil {
-			p.toResume = map[*playerImpl]struct{}{}
-		}
-		p.toResume[pl] = struct{}{}
-	}
-	return nil
-}
-
-func (p *players) resume() error {
-	// playerImpl's Play can touch p. Avoid the deadlock.
-	p.cond.L.Lock()
-	players := map[*playerImpl]struct{}{}
-	for pl := range p.toResume {
-		players[pl] = struct{}{}
-		delete(p.toResume, pl)
-	}
-	p.cond.L.Unlock()
-
-	for pl := range players {
-		pl.Play()
-		if err := pl.Err(); err != nil {
-			return err
-		}
-	}
-	return nil
-}
-
-var thePlayers = &players{
-	cond: sync.NewCond(&sync.Mutex{}),
-}
-
-func (c *context) NewPlayer(src io.Reader) Player {
-	p := &player{
-		p: &playerImpl{
-			context: c,
-			src:     src,
-			volume:  1,
-		},
-	}
-	runtime.SetFinalizer(p, (*player).Close)
-	return p
-}
-
-func (p *player) Err() error {
-	return p.p.Err()
-}
-
-func (p *playerImpl) Err() error {
-	p.m.Lock()
-	defer p.m.Unlock()
-
-	return p.err
-}
-
-func (p *player) Play() {
-	p.p.Play()
-}
-
-func (p *playerImpl) Play() {
-	// Call Play asynchronously since AudioQueuePrime and AudioQueuePlay might take long.
-	ch := make(chan struct{})
-	go func() {
-		p.m.Lock()
-		defer p.m.Unlock()
-		close(ch)
-		p.playImpl()
-	}()
-
-	// Wait until the mutex is locked in the above goroutine.
-	<-ch
-}
-
-func (p *playerImpl) playImpl() {
-	if p.err != nil {
-		return
-	}
-	if p.state != playerPaused {
-		return
-	}
-
-	if p.audioQueue == nil {
-		audioQueue, audioQueueBuffers, err := p.context.audioQueuePool.Get()
-		if err != nil {
-			p.setErrorImpl(err)
-			return
-		}
-		p.audioQueue = audioQueue
-		p.unqueuedBufs = audioQueueBuffers
-		C.AudioQueueSetParameter(p.audioQueue, C.kAudioQueueParam_Volume, C.AudioQueueParameterValue(p.volume))
-
-		p.m.Unlock()
-		thePlayers.add(p, p.audioQueue)
-		p.m.Lock()
-	}
-
-	buf := make([]byte, p.context.maxBufferSize())
-	for len(p.buf) < p.context.maxBufferSize() {
-		n, err := p.src.Read(buf)
-		if err != nil && err != io.EOF {
-			p.setErrorImpl(err)
-			return
-		}
-		p.buf = append(p.buf, buf[:n]...)
-		if err == io.EOF {
-			p.eof = true
-			break
-		}
-	}
-
-	bufs := make([]C.AudioQueueBufferRef, len(p.unqueuedBufs))
-	copy(bufs, p.unqueuedBufs)
-	var unenqueued []C.AudioQueueBufferRef
-	for _, buf := range bufs {
-		queued, err := p.appendBufferImpl(buf)
-		if err != nil {
-			p.setErrorImpl(err)
-			return
-		}
-		if !queued {
-			unenqueued = append(unenqueued, buf)
-		}
-	}
-	p.unqueuedBufs = unenqueued
-	if len(p.unqueuedBufs) == 2 && p.eof {
-		p.state = playerPaused
-		return
-	}
-
-	for {
-		if osstatus := C.AudioQueuePrime(p.audioQueue, 0, nil); osstatus != C.noErr {
-			// AudioQueuePrime might fail just after recovering from Siri.
-			if osstatus == C.AVAudioSessionErrorCodeSiriIsRecording {
 			time.Sleep(10 * time.Millisecond)
-				continue
+			goto try
 		}
-			p.setErrorImpl(fmt.Errorf("readerdriver: AudioQueuePrime failed: %d", osstatus))
+		return fmt.Errorf("readerdriver: AudioQueueStart failed: %d", osstatus)
-			return
 	}
-		break
-	}
-
-	if osstatus := C.AudioQueueStart(p.audioQueue, nil); osstatus != C.noErr {
-		p.setErrorImpl(fmt.Errorf("readerdriver: AudioQueueStart failed: %d", osstatus))
-		return
-	}
-
-	p.state = playerPlay
-}
-
-func (p *player) Pause() {
-	p.p.Pause()
-}
-
-func (p *playerImpl) Pause() {
-	p.m.Lock()
-	defer p.m.Unlock()
-
-	if p.err != nil {
-		return
-	}
-	if p.state != playerPlay {
-		return
-	}
-	if p.audioQueue == nil {
-		return
-	}
-
-	if osstatus := C.AudioQueuePause(p.audioQueue); osstatus != C.noErr && p.err == nil {
-		p.setErrorImpl(fmt.Errorf("readerdriver: AudioQueuePause failed: %d", osstatus))
-		return
-	}
-	p.state = playerPaused
-}
-
-func (p *player) Reset() {
-	p.p.Reset()
-}
-
-func (p *playerImpl) Reset() {
-	p.m.Lock()
-	defer p.m.Unlock()
-	p.resetImpl()
-}
-
-func (p *playerImpl) resetImpl() {
-	if p.err != nil {
-		return
-	}
-	if p.state == playerClosed {
-		return
-	}
-	if p.audioQueue == nil {
-		return
-	}
-
-	// AudioQueueReset is not efficient (#1650, #1680).
-	// Discard the current AudioQueue and recreate one when playing this player again.
-	if err := p.closeAudioQueue(); err != nil {
-		p.setErrorImpl(err)
-		return
-	}
-
-	p.state = playerPaused
-	p.buf = p.buf[:0]
-	p.eof = false
-	thePlayers.cond.Signal()
-}
-
-func (p *player) IsPlaying() bool {
-	return p.p.IsPlaying()
-}
-
-func (p *playerImpl) IsPlaying() bool {
-	p.m.Lock()
-	defer p.m.Unlock()
-
-	return p.state == playerPlay
-}
-
-func (p *player) Volume() float64 {
-	return p.p.Volume()
-}
-
-func (p *playerImpl) Volume() float64 {
-	p.m.Lock()
-	defer p.m.Unlock()
-	return p.volume
-}
-
-func (p *player) SetVolume(volume float64) {
-	p.p.SetVolume(volume)
-}
-
-func (p *playerImpl) SetVolume(volume float64) {
-	p.m.Lock()
-	defer p.m.Unlock()
-
-	p.volume = volume
-	if p.audioQueue == nil {
-		return
-	}
-	C.AudioQueueSetParameter(p.audioQueue, C.kAudioQueueParam_Volume, C.AudioQueueParameterValue(volume))
-}
-
-func (p *player) UnplayedBufferSize() int {
-	return p.p.UnplayedBufferSize()
-}
-
-func (p *playerImpl) UnplayedBufferSize() int {
-	p.m.Lock()
-	defer p.m.Unlock()
-	return len(p.buf)
-}
-
-func (p *player) Close() error {
-	runtime.SetFinalizer(p, nil)
-	return p.p.Close()
-}
-
-func (p *playerImpl) Close() error {
-	p.m.Lock()
-	defer p.m.Unlock()
-	return p.closeImpl()
-}
-
-func (p *playerImpl) closeImpl() error {
-	if err := p.closeAudioQueue(); err != nil && p.err == nil {
-		// setErrorImpl calls closeImpl. Do not call this.
-		p.err = err
-	}
-
-	p.state = playerClosed
-	return p.err
-}
-
-func (p *playerImpl) closeAudioQueue() error {
-	if p.audioQueue == nil {
-		return nil
-	}
-
-	// Even if reuseLater is true, AudioQueuePause is not efficient for reusing.
-	// AudioQueueStart takes long if the AudioQueueStop is not called.
-
-	// AudioQueueStop might invoke AudioQueueReset. Unlock the mutex here to avoid a deadlock.
-	q := p.audioQueue
-	p.m.Unlock()
-	osstatus := C.AudioQueueStop(q, C.true)
-	p.m.Lock()
-
-	if osstatus != C.noErr && p.err == nil {
-		return fmt.Errorf("readerdriver: AudioQueueStop failed: %d", osstatus)
-	}
-
-	// All the AudioQueueBuffers are already dequeued. It is safe to dispose the AudioQueue and its buffers.
-	if err := p.context.audioQueuePool.Put(p.audioQueue); err != nil && p.err == nil {
-		return err
-	}
-
-	p.m.Unlock()
-	thePlayers.remove(p.audioQueue)
-	p.m.Lock()
-	p.audioQueue = nil
 	return nil
 }
 
 //export ebiten_readerdriver_render
 func ebiten_readerdriver_render(inUserData unsafe.Pointer, inAQ C.AudioQueueRef, inBuffer C.AudioQueueBufferRef) {
-	p := thePlayers.get(inAQ)
+	theContext.cond.L.Lock()
-	// The player might be already closed.
+	defer theContext.cond.L.Unlock()
-	if p == nil {
+	theContext.unqueuedBuffers = append(theContext.unqueuedBuffers, inBuffer)
-		return
+	theContext.cond.Signal()
-	}
-
-	queued, err := p.appendBuffer(inBuffer)
-	if err != nil {
-		p.setError(err)
-		return
-	}
-	if queued {
-		return
-	}
-
-	p.m.Lock()
-	defer p.m.Unlock()
-	p.unqueuedBufs = append(p.unqueuedBufs, inBuffer)
-	if len(p.unqueuedBufs) == 2 && p.eof {
-		p.resetImpl()
-	}
-}
-
-func (p *playerImpl) appendBuffer(inBuffer C.AudioQueueBufferRef) (bool, error) {
-	p.m.Lock()
-	defer p.m.Unlock()
-	return p.appendBufferImpl(inBuffer)
-}
-
-func (p *playerImpl) appendBufferImpl(inBuffer C.AudioQueueBufferRef) (bool, error) {
-	if p.eof && len(p.buf) == 0 {
-		return false, nil
-	}
-
-	oneBufferSize := p.context.oneBufferSize()
-	n := oneBufferSize
-	if len(p.buf) < n {
-		n = len(p.buf)
-	}
-	buf := p.buf[:n]
-
-	for i, b := range buf {
-		*(*byte)(unsafe.Pointer(uintptr(inBuffer.mAudioData) + uintptr(i))) = b
-	}
-	for i := len(buf); i < oneBufferSize; i++ {
-		*(*byte)(unsafe.Pointer(uintptr(inBuffer.mAudioData) + uintptr(i))) = 0
-	}
-
-	if osstatus := C.AudioQueueEnqueueBuffer(p.audioQueue, inBuffer, 0, nil); osstatus != C.noErr {
-		// This can happen just after resetting.
-		if osstatus == C.kAudioQueueErr_EnqueueDuringReset {
-			return false, nil
-		}
-		return false, fmt.Errorf("readerdriver: AudioQueueEnqueueBuffer failed: %d", osstatus)
-	}
-
-	p.buf = p.buf[n:]
-	thePlayers.cond.Signal()
-	return true, nil
-}
-
-func (p *playerImpl) setError(err error) {
-	p.m.Lock()
-	defer p.m.Unlock()
-	p.setErrorImpl(err)
-}
-
-func (p *playerImpl) setErrorImpl(err error) {
-	p.err = err
-	p.closeImpl()
-}
-
-func (p *playerImpl) canReadSourceToBuffer() bool {
-	p.m.Lock()
-	defer p.m.Unlock()
-
-	if p.eof {
-		return false
-	}
-	return len(p.buf) < p.context.maxBufferSize()
-}
-
-func (p *playerImpl) readSourceToBuffer() {
-	p.m.Lock()
-	defer p.m.Unlock()
-
-	if p.err != nil {
-		return
-	}
-	if p.state == playerClosed {
-		return
-	}
-
-	maxBufferSize := p.context.maxBufferSize()
-	if len(p.buf) >= maxBufferSize {
-		return
-	}
-
-	buf := make([]byte, maxBufferSize)
-	n, err := p.src.Read(buf)
-
-	if err != nil && err != io.EOF {
-		p.setError(err)
-		return
-	}
-
-	p.buf = append(p.buf, buf[:n]...)
-	if err == io.EOF && len(p.buf) == 0 {
-		p.eof = true
-	}
 }
 
 //export ebiten_readerdriver_setGlobalPause
 func ebiten_readerdriver_setGlobalPause() {
-	thePlayers.suspend()
+	theContext.Suspend()
 }
 
 //export ebiten_readerdriver_setGlobalResume
 func ebiten_readerdriver_setGlobalResume() {
-	thePlayers.resume()
+	theContext.Resume()
 }

audio/internal/readerdriver/driver_ios.go

@@ -0,0 +1,24 @@
+// 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.
+
+//go:build darwin && ios
+// +build darwin,ios
+
+package readerdriver
+
+// 12288 seems necessary at least on iPod touch (7th).
+// With 48000[Hz] stereo, the maximum delay is (12288 / 4 / 2 [samples]) / 48000 [Hz] = 0.032 [sec].
+// '4' is float32 size in bytes. '2' is a number of channels for stereo.
+
+const bufferSizeInBytes = 12288

audio/internal/readerdriver/driver_macos.go

@@ -19,3 +19,5 @@ package readerdriver
 
 // #cgo LDFLAGS: -framework AppKit
 import "C"
+
+const bufferSizeInBytes = 2048

audio/internal/readerdriver/player_unix.go

@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build aix || dragonfly || freebsd || hurd || illumos || linux || netbsd || openbsd || solaris
+//go:build aix || darwin || dragonfly || freebsd || hurd || illumos || linux || netbsd || openbsd || solaris
-// +build aix dragonfly freebsd hurd illumos linux netbsd openbsd solaris
+// +build aix darwin dragonfly freebsd hurd illumos linux netbsd openbsd solaris
 
 package readerdriver