(WIP) David Haywood's Homepage - 模擬器

2012.01.18

Sliver Place

Integrating FLAC isn’t the only thing I’ve been working on lately.
After the initial work on FLAC (prior to the CHD bit) I decided to
integrate some proper JPEG decoding libraries into MAME.

Why? Well, there is one game, which has been running in MAME for a
while which actually uses JPEG decoder chips on the PCB. This game
is the rather obscure ‘Sliver’. As a game, it’s not even remotely
interesting, or good, but from a hardware perspective the pair of
Zoran chips used to decode the JPEG images stored in the ROMs make
it an interesting case.

Until recently MAME has simply loaded an extra ‘fake’ rom with the
JPEG images pre-decoded, and used a look-up table in the driver to
convert the addresses requested by the game for the JPEGS into
addresses where our pre-decoded bitmaps were stored. Obviously this
isn’t how the hardware worked ;-)

By integrating the JPEG library I’ve managed to remove the fake ROM,
and can now point the decoder directly at the real JPEG data in roms
as and when it’s requested by the game.

http://mamedev.emulab.it/haze/pics2012/sliver01.png
http://mamedev.emulab.it/haze/pics2012/sliver02.png

Note, you can see ugly JPEG artifacting on the game screen, they
obviously didn’t compress the images with very high quality
settings ;-)

From an end-users perspective, the game still runs and plays exactly
how it did before, but from a MAME perspective the emulation is now
better, and we have a JPEG library to play with if we want it, maybe
as an option when creating screen-shots at high resolutions where PNG
becomes excessively large? Either way, it’s there and could be put
to further use.

There is one other game which uses the same JPEG decoder chips on the
board Magic the Gathering: Armageddon (Progettoemma link due to MAWS
being down after it was used to hack MameWorld) Currently that game
doesn’t work, but Phil Bennett was last seen getting some 3D out of
it, so having a JPEG decoder should help him get the correct textures,
which are encoded as JPEGs in the ROM.

As with the FLAC stuff, thanks also goes to R.Belmont for ensuring it
compiles / works on Linux and Mac environments.
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來源：http://mamedev.emulab.it/haze/2012/01/18/sliver-place/

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