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Re: Sub-channel support for CDs [Re: Fake Shemp] #106498 07/12/16 12:08 PM
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Now that he's (almost) done hooking it up in Yabause on one of their branches he's released it to other emudevs.

Re: Sub-channel support for CDs [Re: Just Desserts] #106500 07/12/16 01:28 PM
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Originally Posted By Just Desserts
Originally Posted By R. Belmont
It probably could even be done with a Saturn if you patched the SH-1 code, now that that's a thing.


Is it now a thing? The last I heard, some guy had dumped the ROM but was refusing to share it because he wanted to have the market cornered for his modchip or something. Have things changed?


More like didn't share it because he's a lazy Aussie bastard.

Re: Sub-channel support for CDs [Re: Just Desserts] #106503 07/12/16 08:05 PM
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Originally Posted By Just Desserts
Is it now a thing? The last I heard, some guy had dumped the ROM but was refusing to share it because he wanted to have the market cornered for his modchip or something. Have things changed?


No, he didn't release it because he wanted to write full documentation to it, not just a binary full of spaghetti code that breaks more things than it fixes. Plus he was doing this next to working on his PhD.

It is because of that work that you can now softmod Saturns with a patched Action Replay (look up Pseudo Saturn).

Re: Sub-channel support for CDs [Re: F1ReB4LL] #106504 07/12/16 08:20 PM
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Originally Posted By F1ReB4LL
Originally Posted By zyrobs
Unlike main channels, subchannel cannot be ripped properly due to lack of error correction on the format (two identical discs will give you different ripped subs).

There are 2 approaches to this problem: 1) Automatic correction of simple 1-bit errors (99.9% of the subchannel dumps become identical on any drive); 2) Careful analyzing of errors in the dumps taken from different copies of the CDs with the same matrix on different drives. Simple tru*cough*rip subs would be totally useless here, also, the question atm is about the format and further emulation logic, not about what dumps to put inside.


If you are doing automatic error correction then why not just pregenerate the entire thing...? They may have errors there on purpose, or as mastering error.

Cross-comparing multiple dumps sounds good in theory, but you need a lot of copies of a game for that, might not be as simple for expensive games or one of a kind prototype discs.

Re: Sub-channel support for CDs [Re: zyrobs] #106507 07/13/16 12:08 AM
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Originally Posted By zyrobs
If you are doing automatic error correction then why not just pregenerate the entire thing...? They may have errors there on purpose, or as mastering error.

You can't pregenerate the entire thing. P-channel layout, EAN sectors layout, philips/sony gap types, etc. - these differ if you simply generate the subs from cues. And a cleaned (only from 1-bit errors!) sub is way better than a 1-pass "dirty" one, because it is verifiable. Mastering 2-bit (and 2+ bit) errors are always untouched and preserved in this case (for example, on the PCECD F1 Circus Special - Pole to Win (Japan) [HRNB20505-4FAAT] disc or on the SS Rockman X3 (Japan) [T-1210GP-00798 2M1 C 64] disc).

Mastering 1-bit errors are common, yes. As for intentional 1-bit errors, I only know the PSX discs with 0x01, 0x02, 0x03 patterns in R-W channels and yes, in this case you shouldn't apply 1-bit correction to R-W channels, because it wipes all the 0x01 bytes. But, hey, dumping process should never be "blindly" automatic, but always under a human guidance.

Originally Posted By zyrobs
Cross-comparing multiple dumps sounds good in theory, but you need a lot of copies of a game for that, might not be as simple for expensive games or one of a kind prototype discs.

Well, AFAIK, Rawdump admin tried to examine that and he was able to quickly sort out all the matching errors from 2 different discs dumped on different drives, though, it's always hard to judge, because you never have a "perfect" dump with all the mastering errors there to compare with.

Again, noone says you shouldn't keep "dirty" subs for the documentation purposes. But for the general public release cleaned verifiable/verified ones are better. And instead of storing the subs externally, like you've proposed above, I'd rather think about the way to keep the list of cleaned errors externally instead (maybe in some kind of xml file, maybe in the log file, maybe in the chd metadata).

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