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  eXtendable
Wad Editor
Latest Version: 1.16 (2009.05.05)
Developed by Csabo
 
MDK

SNI files are supported, they contain WAV sounds.
MTI and MTO files are supported, but have problems. MTI files have multiple image entries (animations), they are not yet supported. The rest are flat textures. XWE can read the format, but I don't have the right palette. According to the developers, "MDK changes the palette often", which is quite a problem for extracting images.
DTI files are supported. They seem to contain the sky background. I only had one file of this type (since I only have the shareware demo), so it may not work properly with all files.
(no screenshot available)