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Format of PocketNES (v9) GBA images:
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???? bytes:  POCKETNES.GBA contents
(optional) 76800 bytes:  Splash screen (raw 240x160 15bit image)
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32 bytes:  ROM title (NULL terminated)
4 bytes:  ROM size
4 bytes:  ROM flags
4 bytes:  Autoscroll value (a.k.a. "sprite following")
1 byte:  Branch hacks, bit 0-3: opcode, bit 4-7: length. (only V9.97 and later)
3 bytes:  Reserved (set to 0)
???? bytes:  ROM contents (.NES format)
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32 bytes:  Next ROM title
etc etc...
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ROM flags:
   Bit 0: Enable PPU speed hack
          (speeds up some games)
   Bit 1: Disable CPU speed hack
          (a few games need this to work, try this if a game seems buggy)
   Bit 2: Use PAL timing
          (sort of..)
   Bit 5: 0=Autoscroll value is a sprite number
          1=Autoscroll value is a memory location
   Everything else:  Reserved (set to 0)