PSP Mai-HiME Bakuretsu! unknown compression

[fatduck]

The contents of this post was deleted because of possible forum rules violation.

[GameZelda]

I have almost uncompressed this, but I haven't been able to figure out this completely.

(Anything is little endian).

Header
4 bytes: "Wb16" ASCII string
4 bytes: Uncompresed file size

Custom-LZSS Compressed blocks (Come immediately after the header).
4 bytes: Compression flags.
32 * 2 bytes: Compressed data.

The "compression flags" are interpreted from the LSB to the MSB (e.g. check compressionFlags & 1).

Compression flags: case 1
2 bytes: Uncompressed data.

Compression flags: case 0
2 bytes: Encoded position + length.

I believe that the encoding used is the following: 5 bits for the length and 11 bits for the position.

Code: Select all

length = ((data & 0x1F) + 2);
bufferDataPos = ((data >> 5) & 0x7FF);

The length is in groups of uint16_t's, so just multiply it by 2 to get the number of bytes.

---

I'm stuck with the position bits. I believe that they use a buffer of 0x2000 uint16_t's (0x4000 bytes) initialized to zero, like in this implementation.

http://www.programmersheaven.com/downlo ... pView.aspx

However, even if the uncompressed result is pretty good, it seems to be wrong. I've tried different buffer initial positions (variable "r" in that implementation) without success.

[fatduck]

Thanks for you help GameZelda! I try to decmpress the first 2K data manually and it seems to work fine!

Strange enough the position are in +ve value!? Anyway, I'll try decompress them all to see if any special case there!