How to decrypt and decompile luac-file from cocos2d-x framework?

Question

I know that the lua version is stored in the 5th byte of the luac file (the header). Here's the first few bytes of a luac file I have:

6D 6D 64 64 74 32

The 5th byte is 74. Is My Luac file LuaJIT bytecode?

I am trying to decompile this file and receive this error by using unluac

Exception in thread "main" java.lang.IllegalStateException: The input file does not have the signature of a valid Lua file.
at unluac.parse.BHeader.<init>(BHeader.java:41)
at unluac.Main.file_to_function(Main.java:71)
at unluac.Main.main(Main.java:42)

and below is error by using luadec (lua 5.1)

'=' expected near '?'

How can I decompile this file type?