Phantasy Star Generation 2:Notes

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Compression

CUE found out the coding algorithm. It's a Lempel-Ziv related one, called Lempel-Ziv Renau.

Structure of files :

  • Bytes $0000 to $000a : header
    • 2 bytes : signature, always "CM"
    • 4 bytes: decoded data length, low endian
    • 4 bytes: encoded data length, low endian
  • From $000a : ENCODED_DATA
  • Then FLAGS. Flags are read bit per bit :
    • if bit = 0, then put one byte from ENCODED_DATA and put into DECODED_STREAM
    • if bit = 1, then the corresponding half-word in ENCODED_DATA is of the form lllloooooooooooo, where l = length and o = offset. Copy then 'length + 3' bytes from DECODED_STREAM[current_position - offset + 1] to DECODED_STREAM[curent_position].
  • Fill the file with $00, up to have a file size dividible by $800.

Files specifications

Graphics files (SGGG)

Maps files

Text files

Animations files