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MAME/MESS PSX MDEC output compared to hardware
#217636 - 03/23/10 04:35 PM
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Does anyone know if the PlayStation 1 MDEC emulation code in mame/machine/psx.c has been compared to actual hardware MDEC output? Is it byte-exact, or is it just an IDCT and YCbCr->RGB estimation? Is there any documentation about such a comparison available that might include an actual hardware memory dump?
If no one really has any of these answers, could anyone direct me to where I might find some answers? Thanks.
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R. Belmont |
Cuckoo for IGAvania
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Reged: 09/21/03
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Posts: 9717
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Loc: ECV-197 The Orville
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Re: MAME/MESS PSX MDEC output compared to hardware
[Re: m35]
#217671 - 03/23/10 09:39 PM
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> Does anyone know if the PlayStation 1 MDEC emulation code in mame/machine/psx.c has > been compared to actual hardware MDEC output? Is it byte-exact, or is it just an IDCT > and YCbCr->RGB estimation? Is there any documentation about such a comparison > available that might include an actual hardware memory dump?
Nobody's done a comparison on that level that I'm aware of, but MAME's MDEC was first to correctly implement a lot of things that common PSX emulators got wrong (e.g. that Cr comes before Cb, not the other way around).
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Re: MAME/MESS PSX MDEC output compared to hardware
[Re: R. Belmont]
#218076 - 03/28/10 03:06 AM
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> Nobody's done a comparison on that level that I'm aware of, but MAME's MDEC was first > to correctly implement a lot of things that common PSX emulators got wrong (e.g. that > Cr comes before Cb, not the other way around).
It also uses the uploaded cosine & quantize tables.
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Re: MAME/MESS PSX MDEC output compared to hardware
[Re: ]
#218126 - 03/28/10 06:55 PM
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Ah smf, I'm happy to have caught your attention
I recently discovered the uploaded (I)DCT cosine table as well, and even just added it to my PSX video format document. I've also been keenly aware of the Cb/Cr swap error thanks to your post about it.
Comparing the various decoders out there (I'll be adding MAME to the list soon), it seems there's only a handful that get it right.
I've been trying to add a 'PSX exact quality' option to my jPSXdec video decoder. Since I only have a PSone and the CD based Gameshark, I don't have easy access to PSX ram, otherwise I'd be dumping it and comparing. MAME's output is the closest thing I have to work with, so I was hoping that careful comparison might have already been done. As it hasn't, I would totally be digging into it right now--if only I had hardware RAM/VRAM dumps of the 24 BPP Tekken 3 or FF9 opening movies.
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