validate audio configuration before connecting

Reject unsupported audio intervals and non-positive buffer sizes.
An interval like 15ms was truncated to 10ms frames while the send
ticker kept the original duration, so packets were produced at a rate
the frame size did not match. Checking at dial time gives a clear
error instead of malformed audio.

Require all three coordinates for positional audio.
Only X was checked, so supplying X without Y or Z wrote a header that
claimed positional data and then read past the values that were
actually provided.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

gumble/gumble/client.go

@@ -125,6 +125,9 @@ func tlsServerName(address string) (string, error) {
 // min(time.Now() + dialer.Timeout, dialer.Deadline), or if the server rejects
 // the client.
 func DialWithDialer(dialer *net.Dialer, config *Config, tlsConfig *tls.Config) (*Client, error) {
+	if err := config.Validate(); err != nil {
+		return nil, err
+	}
 	start := time.Now()
 
 	rawConn, err := dialer.Dial("tcp", config.Address)

gumble/gumble/config.go

@@ -1,6 +1,7 @@
 package gumble
 
 import (
+	"fmt"
 	"time"
 )
 
@@ -43,6 +44,22 @@ func NewConfig() *Config {
 	}
 }
 
+// Validate checks values that are used by the audio ticker and encoder.
+func (c *Config) Validate() error {
+	switch c.AudioInterval {
+	case 10 * time.Millisecond, 20 * time.Millisecond, 40 * time.Millisecond, 60 * time.Millisecond:
+	default:
+		return fmt.Errorf("gumble: AudioInterval must be 10ms, 20ms, 40ms, or 60ms")
+	}
+	if c.AudioDataBytes <= 0 {
+		return fmt.Errorf("gumble: AudioDataBytes must be positive")
+	}
+	if c.Buffers <= 0 {
+		return fmt.Errorf("gumble: Buffers must be positive")
+	}
+	return nil
+}
+
 // Attach is an alias of c.Listeners.Attach.
 func (c *Config) Attach(l EventListener) Detacher {
 	return c.Listeners.Attach(l)

gumble/gumble/config_regression_test.go

@@ -0,0 +1,20 @@
+package gumble
+
+import (
+	"testing"
+	"time"
+)
+
+// Regression: arbitrary intervals were truncated to 10 ms frames while the
+// ticker kept the original duration, producing malformed audio timing.
+func TestConfigValidateRejectsUnsupportedAudioInterval(t *testing.T) {
+	config := NewConfig()
+	config.AudioInterval = 15 * time.Millisecond
+	if err := config.Validate(); err == nil {
+		t.Fatal("invalid audio interval was accepted")
+	}
+	config.AudioInterval = 60 * time.Millisecond
+	if err := config.Validate(); err != nil {
+		t.Fatalf("valid audio interval rejected: %v", err)
+	}
+}

gumble/gumble/conn.go

@@ -80,7 +80,10 @@ func (c *Conn) WriteAudio(format, target byte, sequence int64, final bool, data
 	header := buff[:1+n+m]
 
 	var positionalLength int
-	if X != nil {
+	if X != nil || Y != nil || Z != nil {
+		if X == nil || Y == nil || Z == nil {
+			return errors.New("gumble: positional audio requires X, Y, and Z")
+		}
 		positionalLength = 3 * 4
 	}