Revert "audio: Bug fix: Fill empty data even when audio is suspended"

This reverts commit 529dddda53.

Updates #975

Reason: This causes PARTIAL_WAKE_LOCK on Android (AudioDirectOut) (#931)

audio/audio.go

@@ -63,11 +63,11 @@ type Context struct {
 	sampleRate int
 	err        error
 	ready      bool
-	suspended  bool
 
 	players map[*playerImpl]struct{}
 
 	m         sync.Mutex
+	semaphore chan struct{}
 }
 
 var (
@@ -75,8 +75,6 @@ var (
 	theContextLock sync.Mutex
 )
 
-var emptyBytes = make([]byte, 256)
-
 // NewContext creates a new audio context with the given sample rate.
 //
 // The sample rate is also used for decoding MP3 with audio/mp3 package
@@ -101,19 +99,16 @@ func NewContext(sampleRate int) (*Context, error) {
 		c:          newContext(sampleRate),
 		players:    map[*playerImpl]struct{}{},
 		inited:     make(chan struct{}),
+		semaphore:  make(chan struct{}, 1),
 	}
 	theContext = c
 
 	h := getHook()
 	h.OnSuspendAudio(func() {
-		c.m.Lock()
-		c.suspended = true
-		c.m.Unlock()
+		c.semaphore <- struct{}{}
 	})
 	h.OnResumeAudio(func() {
-		c.m.Lock()
-		c.suspended = false
-		c.m.Unlock()
+		<-c.semaphore
 	})
 
 	h.AppendHookOnBeforeUpdate(func() error {
@@ -460,14 +455,10 @@ func (p *playerImpl) read() ([]byte, bool) {
 
 	const bufSize = 2048
 
-	// If audio is suspended, fill zero values not to cause delay (#975).
-	// TODO: Oto's players should be able to be suspended and resumed.
-	p.context.m.Lock()
-	s := p.context.suspended
-	p.context.m.Unlock()
-	if s {
-		return emptyBytes, true
-	}
+	p.context.semaphore <- struct{}{}
+	defer func() {
+		<-p.context.semaphore
+	}()
 
 	newBuf := make([]byte, bufSize-len(p.buf))
 	n, err := p.src.Read(newBuf)