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Help with determining Compression type

Started by DackR, June 13, 2015, 11:52:21 PM

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Okay- So some of you know about the Marvelous:Another Treasure Island translation project that I picked up from Tashi. So far, I've identified the type of compression used for the graphics and a good portion of the data. Most of it uses a form of LZ compression very similar to that used by Alttp.

I've come across something related to the compression/encoding used to store menu information that I'd like some help on.

I've located the approximate location where the Journal selection menu is stored (ROM Offset E2874). This is the menu at the beginning where you can select a previously saved game, or a new game.

Now, I'm able to decompress the data using the same method that I've used successfully for most of the data in the game. It gives me a tilemap that comes out to 7kb of data for the menu that looks pretty much (At least the first 1kb) exactly like it does when the game decompresses it and stores it in VRAM.

However, I'm unable to re-compress the data using the same method. The re-compressed data comes out much smaller than the original compressed data... Therein lies my issue. I've tried several different methods of re-compressing the data, but all of them end up borking it up.

So... I guess I was wondering if anyone else wanted to give it a go? I'm probably missing something simple. I'm going to keep hammering away at it anyway, but it was bothering me enough that I figured I'd ask.