chore: support 4 byte headers in voice example

Author: cactysman

_examples/voice/voice.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bytes"
 	"context"
 	"encoding/binary"
 	"io"
@@ -78,6 +79,19 @@ func play(client *bot.Client, closeChan chan os.Signal) {
 	closeChan <- syscall.SIGTERM
 }
 
+// Test if the header is 4 bytes in size for some obscure and unknown reason.
+func has4BitHeaders(file *os.File) (bool, error) {
+	var pad [2]byte
+	_, err := file.ReadAt(pad[:], 2)
+	if err != nil {
+		return false, err
+	}
+	if bytes.Equal(pad[:], []byte{0, 0}) {
+		return true, nil
+	}
+	return false, nil
+}
+
 func writeOpus(w io.Writer) {
 	file, err := os.Open("nico.dca")
 	if err != nil {
@@ -86,10 +100,21 @@ func writeOpus(w io.Writer) {
 	ticker := time.NewTicker(time.Millisecond * 20)
 	defer ticker.Stop()
 
+	// support flag for skipping 2 bytes after each header
+	h4, err := has4BitHeaders(file)
+	if err != nil {
+		panic("error reading file: " + err.Error())
+	}
+
 	var frameLen int16
 	// Don't wait for the first tick, run immediately.
 	for ; true; <-ticker.C {
 		err = binary.Read(file, binary.LittleEndian, &frameLen)
+
+		if err == nil && h4 {
+			_, err = file.Seek(2, io.SeekCurrent)
+		}
+
 		if err != nil {
 			if err == io.EOF {
 				_ = file.Close()