diff --git a/vipsong.py b/vipsong.py
index f5a3bec..3c81cbd 100644
--- a/vipsong.py
+++ b/vipsong.py
@@ -1,5 +1,5 @@
 #!/usr/bin/env python3
-import os, sys, glob, struct, base64, json
+import os, sys, glob, struct, base64, json, io
 from pathlib import Path
 from typing import Optional
 from Crypto.Cipher import AES
@@ -12,11 +12,53 @@ from pydub import AudioSegment
 
 NCM_MAGIC = b"CTENFDAM"
 CORE_KEY = b"hzHRAmso5kInbaxW"
+META_KEY = bytes.fromhex("2331346C6A6B5F215C5D2630553C2728")
 META_PREFIX = b"163 key(D't modify):"
+KUGOU_KEY_PATH = Path(__file__).parent / "kugou_key.xz"
+
+_FORMAT_MAP = {
+    "mp3": "mp3",
+    "flac": "flac",
+    "wav": "wav",
+    "ogg": "ogg",
+    "m4a": "mp4",
+    "mp4": "mp4",
+}
+
+stats = {"success": 0, "failed": 0, "files": []}
+kgm_decoder = None
 
 def _u32le(data, pos):
     return struct.unpack(b"<I", data[pos:pos+4])[0]
 
+def _sniff_container(header):
+    """从魔术字节检测音频容器类型。"""
+    if len(header) >= 3 and header[:3] == b"ID3":
+        return "mp3"
+    if len(header) >= 2 and header[0] == 0xFF and (header[1] & 0xE0) == 0xE0:
+        return "mp3"
+    if len(header) >= 4 and header[:4] == b"fLaC":
+        return "flac"
+    if len(header) >= 4 and header[:4] == b"OggS":
+        return "ogg"
+    if len(header) >= 12 and header[:4] == b"RIFF" and header[8:12] == b"WAVE":
+        return "wav"
+    if len(header) >= 12 and header[4:8] == b"ftyp":
+        return "mp4"
+    return None
+
+def _extension_for(fmt):
+    """将格式名称映射为文件后缀。"""
+    mapping = {
+        "mp3": "mp3",
+        "flac": "flac",
+        "wav": "wav",
+        "ogg": "ogg",
+        "m4a": "m4a",
+        "mp4": "m4a",
+    }
+    return mapping.get(fmt, "mp3")
+
 def ncm_stream_bytes(key):
     sbox = bytearray(range(256))
     j = 0
@@ -210,6 +252,16 @@ def _add_tags(output_path, tags, cover=None):
     except Exception:
         pass
 
+def _convert_audio(raw, container, out_fmt, output_path):
+    """将解密后的原始音频转码为目标格式。"""
+    src_fmt = _FORMAT_MAP.get(container, container)
+    dst_fmt = _FORMAT_MAP.get(out_fmt, out_fmt)
+    if src_fmt == dst_fmt:
+        Path(output_path).write_bytes(raw)
+    else:
+        audio = AudioSegment.from_file(io.BytesIO(raw), format=src_fmt)
+        audio.export(output_path, format=dst_fmt)
+
 def convert_file(file_path, output_fmt, delete_flag):
     global stats, kgm_decoder
     file_path = str(Path(file_path).resolve())
@@ -339,11 +391,11 @@ def main():
             convert_file(f, output_fmt, delete_flag)
         print_stats()
         return
-    print("=* 50")
+    print("=" * 50)
     print("  vipsong - Music Format Converter")
     print("  Support: .ncm (NetEase)  .kgm/.vpr (KuGou)")
     print("  Output:  mp3 / flac / wav / ogg / m4a")
-    print("=* 50")
+    print("=" * 50)
     print("Commands:")
     print("  <filepath>     Convert file or glob pattern (e.g. *.ncm)")
     print("  -f <format>    Output format (default: mp3)")