Attempt to fix a bug that can randomly drop audio streams.

gumble/gumble/audio.go

@@ -86,6 +86,8 @@ type AudioPacket struct {
 	Sender *User
 	Target *VoiceTarget
 	Final  bool
+	// Channels is the number of interleaved PCM channels in AudioBuffer.
+	Channels int
 	// LocallyMuted and LocalMuteGeneration snapshot the receiver's local mute
 	// state when the packet entered the playback queue.
 	LocallyMuted        bool

gumble/gumble/audiocodec.go

@@ -50,6 +50,7 @@ type AudioEncoder interface {
 // AudioDecoder decodes an encoded byte slice to a chunk of PCM audio samples.
 type AudioDecoder interface {
 	ID() int
+	Channels() int
 	Decode(data []byte, frameSize int) ([]int16, error)
 	Reset()
 }

gumble/gumble/handlers.go

@@ -152,6 +152,7 @@ func (c *Client) handleUDPTunnel(buffer []byte) error {
 		Client:              c,
 		Sender:              user,
 		Final:               final,
+		Channels:            decoder.Channels(),
 		LocallyMuted:        locallyMuted,
 		LocalMuteGeneration: localMuteGeneration,
 		Target: &VoiceTarget{

gumble/gumbleopenal/stream.go

@@ -41,6 +41,23 @@ func shouldStartPlayback(state openal.State, queued int32, final bool) bool {
 	return state != openal.Playing && queued > 0 && (queued >= playbackPrebufferBuffers || final)
 }
 
+func playbackLayout(packet *gumble.AudioPacket) (openal.Format, int, bool) {
+	if packet == nil || len(packet.AudioBuffer) == 0 {
+		return 0, 0, false
+	}
+	switch packet.Channels {
+	case gumble.AudioMonoChannels:
+		return openal.FormatMono16, len(packet.AudioBuffer), true
+	case gumble.AudioChannels:
+		if len(packet.AudioBuffer)%gumble.AudioChannels != 0 {
+			return 0, 0, false
+		}
+		return openal.FormatStereo16, len(packet.AudioBuffer) / gumble.AudioChannels, true
+	default:
+		return 0, 0, false
+	}
+}
+
 type playbackCommand struct {
 	gain       float32
 	muted      bool
@@ -550,14 +567,14 @@ func (s *Stream) OnAudioStream(e *gumble.AudioStreamEvent) {
 			}
 
 			var boost uint16 = uint16(1)
-			samples := len(packet.AudioBuffer)
-			if samples == 0 {
+			if len(packet.AudioBuffer) == 0 {
 				if shouldStartPlayback(source.State(), source.BuffersQueued(), packet.Final) {
 					source.Play()
 				}
 				continue
 			}
-			if samples > cap(raw)/2 {
+			format, samples, validLayout := playbackLayout(packet)
+			if !validLayout || len(packet.AudioBuffer) > cap(raw)/2 {
 				continue
 			}
 
@@ -569,13 +586,7 @@ func (s *Stream) OnAudioStream(e *gumble.AudioStreamEvent) {
 				recordBuffer = make([]int16, len(packet.AudioBuffer)*gumble.AudioChannels)
 			}
 
-			// Check if sample count suggests stereo data
-			isStereo := samples > gumble.AudioDefaultFrameSize && samples%2 == 0
-			format := openal.FormatMono16
-			if isStereo {
-				format = openal.FormatStereo16
-				samples = samples / 2
-			}
+			isStereo := packet.Channels == gumble.AudioChannels
 
 			rawPtr := 0
 			if isStereo {

gumble/gumbleopenal/stream_test.go

@@ -32,6 +32,24 @@ func TestShouldStartPlayback(t *testing.T) {
 	}
 }
 
+func TestPlaybackLayoutUsesExplicitStereoChannelCount(t *testing.T) {
+	packet := &gumble.AudioPacket{
+		Channels:    gumble.AudioChannels,
+		AudioBuffer: make(gumble.AudioBuffer, gumble.AudioDefaultFrameSize),
+	}
+
+	format, frames, ok := playbackLayout(packet)
+	if !ok {
+		t.Fatal("expected a valid short stereo packet")
+	}
+	if format != openal.FormatStereo16 {
+		t.Fatalf("format = %v, want stereo", format)
+	}
+	if frames != gumble.AudioDefaultFrameSize/gumble.AudioChannels {
+		t.Fatalf("frames = %d, want %d", frames, gumble.AudioDefaultFrameSize/gumble.AudioChannels)
+	}
+}
+
 func TestSendOutgoingAudioStopsWhileSendIsBlocked(t *testing.T) {
 	stop := make(chan struct{})
 	outgoing := make(chan gumble.AudioBuffer)

gumble/opus/opus.go

@@ -88,6 +88,10 @@ func (*Decoder) ID() int {
 	return ID
 }
 
+func (d *Decoder) Channels() int {
+	return d.channels
+}
+
 func (d *Decoder) Decode(data []byte, frameSize int) ([]int16, error) {
 	// Allocate buffer for stereo - frameSize is per channel
 	pcm := make([]int16, frameSize*gumble.AudioChannels)