onitama / spihsp

Susie plugin for Hot Soup Processor 2 and 3

spihsp

spihsp is a Susie plugin package for Hot Soup Processor 2 and 3.

• axdpm.spi: DPM archive (*.dpm) unpacker, supports HSP 3.22 or older.
• axdpm33.spi: DPM archive (*.dpm) unpacker, supports HSP 3.3 or later.
• axdpmex.spi: Same as axdpm.spi, but this one supports in-EXE archive.
• axdpmex33.spi: Same as axdpm33.spi, but this one supports in-EXE archive.

What is Susie plugin?

Susie is an old-school picture viewer for Windows, which can load additional formats by adding Susie plugins (*.spi). In Japan, Susie plugin is often used for decoding custom image formats inside a game.

There are several picture viewers that supports Susie plugin. For example:

• Susie
• Linar
• picture effecter
• stereophotomaker
• vix
• A to B converter
• ACDSee (commercial)

My favorite is Linar for browsing, and AtoB Converter for batch conversion.

Note

• axdpm can decrypt only archives that do not specify the encryption key by chdpm. (because it is hard to determine the encryption key 100% automatically, and axdpm does not have an interface for specifying encryption key. FYI, decryption routine is exactly identical to the regular decoding.)
  • In such case, you may want to use a HSP decompiler to get the encryption key. Try HSPdeco and search chdpm from the decompiled source code.
• HSP file decryption routine uses two 8 bit encryption keys. Therefore, possible key combinations are only 65,536 patterns. In fact, you can try brute force decoding even if you cannot get the encryption key. A bundled tool dpmatt is a simple implementation of that.
• If target EXE is compressed by a packer (e.g. UPX), axdpm will fail at archive detection. Please unpack the EXE by hand beforehand (see the following section for details).
• UNDPM32.DLL is a DPM unpacker library that respects Common Archiver Project API. axdpm.spi can work without it.
• Any use of the software is entirely at your own risk.

How to unpack HSP-EXE

If target EXE is compressed by a packer, you need to unpack the EXE by hand.

1. Open the target EXE in a hex editor (e.g. Hex Workshop).
2. Search for "DPMX" from the tail of file. Then, cut the "DPMX" itself, and the part after it. (Note that the removed DPMX section is needed a little later. So please save it to somewhere.)
3. Unpack the modified EXE by using unpacker tool. (e.g. UPX can be unpacked by UPX)
4. Reopen the unpacked EXE in a hex editor, and recover the preserved DPMX section into the tail of file.

Checksum of HSP-EXE

For details of the checksum, see hspsum.cpp in source code package.