+#define CHD_CODEC_NONE 0
+#define CHD_CODEC_ZLIB CHD_MAKE_TAG('z','l','i','b')
+/* general codecs with CD frontend */
+#define CHD_CODEC_CD_ZLIB CHD_MAKE_TAG('c','d','z','l')
+#define CHD_CODEC_CD_LZMA CHD_MAKE_TAG('c','d','l','z')
+#define CHD_CODEC_CD_FLAC CHD_MAKE_TAG('c','d','f','l')
+