Synchronize audio encoder selection

client.go

@@ -99,7 +99,7 @@ func (b *Barnard) connect(reconnect bool) bool {
 	})
 
 	// Initialize stereo encoder for file playback
-	b.Client.AudioEncoderStereo = opus.NewStereoEncoder()
+	b.Client.SetStereoEncoder(opus.NewStereoEncoder())
 
 	// Initialize file player
 	b.FileStreamMutex.Lock()

gumble/gumble/audio.go

@@ -53,28 +53,30 @@ type AudioStreamEvent struct {
 type AudioBuffer []int16
 
 func (a AudioBuffer) writeAudio(client *Client, seq int64, final bool) error {
-	// Always use the mono encoder for voice transmission. The stereo
-	// encoder is only used when explicitly enabled for file playback.
+	// Encoding shares mutable codec state with server-configuration and file
+	// playback changes. Keep the client read lock through Encode and Reset so a
+	// stereo encoder cannot be replaced or reset while it is in use.
+	client.volatile.RLock()
 	encoder := client.AudioEncoder
-	if client.IsStereoEncoderEnabled() && client.AudioEncoderStereo != nil {
+	if client.useStereoEncoder && client.AudioEncoderStereo != nil {
 		encoder = client.AudioEncoderStereo
 	}
 	if encoder == nil {
+		client.volatile.RUnlock()
 		return nil
 	}
-	dataBytes := client.Config.AudioDataBytes
-	raw, err := encoder.Encode(a, len(a), dataBytes)
+	raw, err := encoder.Encode(a, len(a), client.Config.AudioDataBytes)
 	if final {
-		defer encoder.Reset()
+		encoder.Reset()
 	}
-	if err != nil {
-		return err
-	}
-
 	var targetID byte
 	if target := client.VoiceTarget; target != nil {
 		targetID = byte(target.ID)
 	}
+	client.volatile.RUnlock()
+	if err != nil {
+		return err
+	}
 	return client.WriteAudio(byte(4), targetID, seq, final, raw, nil, nil, nil)
 }
 

gumble/gumble/client.go

@@ -343,6 +343,13 @@ func (c *Client) Send(message Message) {
 	message.writeMessage(c)
 }
 
+// SetStereoEncoder installs the encoder used for stereo file playback.
+func (c *Client) SetStereoEncoder(encoder AudioEncoder) {
+	c.volatile.Lock()
+	defer c.volatile.Unlock()
+	c.AudioEncoderStereo = encoder
+}
+
 // EnableStereoEncoder switches to stereo encoding for file playback.
 func (c *Client) EnableStereoEncoder() {
 	c.volatile.Lock()