Keep OpenAL jitter playback continuous

gumble/gumbleopenal/stream.go

@@ -51,9 +51,17 @@ type Recorder interface {
 const recorderOutgoingSource uint32 = ^uint32(0)
 
 const (
-	maxBufferSize = 11520 // Max frame size (2880) * bytes per stereo sample (4)
+	maxBufferSize    = 11520 // Max frame size (2880) * bytes per stereo sample (4)
+	jitterMinPackets = 3
+	jitterMaxPackets = 10
 )
 
+// jitterPlaybackReady holds the initial playout delay only once. Requiring
+// the minimum on every packet drains and refills the renderer in bursts.
+func jitterPlaybackReady(started bool, buffered int) bool {
+	return started || buffered >= jitterMinPackets
+}
+
 var (
 	ErrState        = errors.New("gumbleopenal: invalid state")
 	ErrMic          = errors.New("gumbleopenal: microphone disconnected or misconfigured")
@@ -451,15 +459,10 @@ func (s *Stream) OnAudioStream(e *gumble.AudioStreamEvent) {
 		}
 
 		// Jitter buffer: collects incoming packets, reorders by
-		// sequence number, and releases them in order after a small
+		// sequence number, and releases them after a small initial delay.
-		// initial delay (3-5 packets / 30-50ms).
-		const (
-			jitterMinPackets = 3  // minimum packets before playout starts
-			jitterMaxPackets = 10 // maximum buffered packets before dropping oldest
-		)
 		var jitterBuf []*gumble.AudioPacket
 		var jitterNextSeq int64
-		var jitterInit bool
+		var jitterInit, jitterStarted bool
 
 		// insertSorted inserts a packet into the jitter buffer sorted
 		// by sequence number.
@@ -509,10 +512,13 @@ func (s *Stream) OnAudioStream(e *gumble.AudioStreamEvent) {
 				jitterInit = true
 			}
 
-			// Only start playing when we have enough buffered packets
+			// Hold only the initial packets. Once playback starts, drain every
-			if len(jitterBuf) < jitterMinPackets {
+			// ready packet so the renderer is fed continuously rather than in
+			// bursts of jitterMinPackets packets.
+			if !jitterPlaybackReady(jitterStarted, len(jitterBuf)) {
 				continue
 			}
+			jitterStarted = true
 
 			// Drain all packets that are ready (in sequence order)
 			for {

gumble/gumbleopenal/stream_regression_test.go

@@ -48,6 +48,18 @@ func TestStopSourceWaitsForWorker(t *testing.T) {
 	<-returned
 }
 
+func TestJitterPlaybackDelayAppliesOnlyAtStartup(t *testing.T) {
+	if jitterPlaybackReady(false, jitterMinPackets-1) {
+		t.Fatal("jitter playback started before initial buffer filled")
+	}
+	if !jitterPlaybackReady(false, jitterMinPackets) {
+		t.Fatal("jitter playback did not start after initial buffer filled")
+	}
+	if !jitterPlaybackReady(true, 1) {
+		t.Fatal("jitter playback paused while refilling after startup")
+	}
+}
+
 func TestRenderRejectsWorkAfterShutdown(t *testing.T) {
 	s := &Stream{renderClosed: true}
 	called := false