Namco's data compression method in Ace Combat 3, Ace Combat 5¹⁾, and Time Crisis.

The Ulz format is an implementation of Lz77 algorithm with a ring buffer.

developed by Junichi Sakai
- the Japanese Time Crisis executable contains the string ulz ver.1.00 J.Sakai
- the Japanese Ace Combat 3 executable contains the string ulz decoder ver.1.05 programmed by Junichi Sakai ²⁾

ULZ is LZR (Lempel–Ziv–Renau)
- LZSS (Lempel–Ziv–Storer–Szymanski) with separate data streams
- optimized for MIPS (32-bit words, few variable bit shifts)

Tools

Timeline

1995: Namco releases Time Crisis (ULZ 1.00)
1999: Namco releases Ace Combat 3 (ULZ 1.05)
2004: Namco releases Ace Combat 5 (ULZ 1.05)
2011-01-04: modder McCuñao posts an incomplete description of ULZ “from a friend” ³⁾
2012-03-11: modder Gipphe analyzes the format ⁴⁾, but gives up – his texts and code is lost
2012-06-20: modder CUE posts incomplete decompression code for Time Crisis and Ace Combat 3 ⁵⁾
2014-02-08: modder esperknight posts incomplete decompression code for Ace Combat 3 ⁶⁾
2014-08-02: esperknight posts full decompression code ⁷⁾
2017-01-10: modder Infrid unites the two separate compression methods into one ⁸⁾

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[PSX] Ace Combat 3 - I'm looking for help, Romxhacking, http://romxhack.esforos.com/post2916

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