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Deunan
They see me rollin'... 
15th-Mar-2014 05:23 pm
Decision has been made, there will be a short production run of GDEMU soon - as in, a few weeks. After that, when I can tell just how many people are actually going to pay for it, I will decide if I will continue or not. More details will follow once I get everything sorted out.

In other news, my testers notified me of some recently done Dreamcast dumps that appear to be broken on GDEMU, so I investigated.
Seems like there is a group, or groups, that started doing GD-ROM dumps using PC drives with a so-called "swap method". I did that too once, other than having slightly different "audio offsets" there is nothing preventing such dumps from working - if done correctly. And that's the key word here. Well, the group(s) in question decided they know better and introduced changes into tracks' positions and lengths - to "fix" things I guess. The worst part is they've just shoved all their changes into .gdi files and typical user has no way of knowing if it's a proper dump or not.

GD-ROM images made using GD drive in Dreamcast are not perfect either, but frankly no CD image format is, or will ever be, unless we store raw EFM stream (assuming we can even read it glitch-free, which is debatable). But small flaws can be corrected if the method is good in principle and the changes are always consistent. For GDIs it means you need to adjust for missing pregaps (not really needed) on data tracks and starting address on audio tracks. My guess is the new dumps were supposed to overcome that, but instead are plain broken.

As an example let's take a look at Chu-Chu Rocket, the PAL version. The new .gdi file says this for tracks 3 and 4:

3 45000 4 2352 "ChuChu Rocket! (Europe) (En,Ja,Fr,De,Es) (Track 03).bin" 0
4 355602 0 2352 "ChuChu Rocket! (Europe) (En,Ja,Fr,De,Es) (Track 04).bin" 0

Track 3 file is 730535904 bytes long, that is 310602 raw sectors. Since it's missing the pregap I mentioned, the actual length of the track is 150+310602=310752.
Let's add this length to it's starting address, to see where it ends: 45000+310752=355752. See the problem? Track 4 starts at 355602, which is less than 355752. This creates an impossible situation where tracks overlap.

But wait, what if we treated this new image just like the old dumps and actually did apply the fix for audio tracks as usual? Then it'd be 355602 plus 150 fix which equals 355752 and it checks out. Yay! Maybe this is the correct way after all, let's investigate further:

18 505295 0 2352 "ChuChu Rocket! (Europe) (En,Ja,Fr,De,Es) (Track 18).bin" 0
19 505819 4 2352 "ChuChu Rocket! (Europe) (En,Ja,Fr,De,Es) (Track 19).bin" 0

Track 18 is audio, 1232448 bytes long, which makes it 524 "sectors". If we add the fix, then it starts at 505295+150=505445, and ends at 505445+524=505969. Oops. Track 19 started already, at 505819... Now track 18 end overlaps with track 19 pregap.

The funny thing is, the situation with track 18 overlapping track 19 will kinda work still, since no code ever tries to acces the pregap, so the collision will never be discovered. But this tells you a lot about quality of this dump. Can it be fixed? Maybe. Question is, why break and fix it, rather than just use a known good dump.

I rest my case.
Comments 
15th-Mar-2014 06:38 pm (UTC) - Put me down for one!
I'll buy one, or even more depending on the price!
17th-Mar-2014 11:21 am (UTC) - Re: Put me down for one!
Yes, put me down for one too. Also following the other project on Assemblergames too...
15th-Mar-2014 06:40 pm (UTC) - that group
Ooh, I know that group. They are big-mouthed pompous buffoons who have no clue on how to manage software standards (as in, their own ripping standards). And they don't even have a decent coder, they just mix and match a dozen different tools for ripping.

Which wouldn't be a problem if they weren't so incredibly obnoxious about how they are better than everyone. Even worse, many people believe that too, on viral levels.

If you ask me, you should just include a note that "rips from these groups are defective, GDEMU only works with backups you make yourself on your Dreamcast", and not bother fixing support for their broken rips. If we are lucky, they may just consider it a wake-up call.
15th-Mar-2014 11:55 pm (UTC) - Re: that group
"rips from these groups are defective, GDEMU only works with backups you make yourself on your Dreamcast" -- it's like 'proper encrypted NDS roms are defective, since they don't work on flashcards, decrypted ones are the only proper dumps possible'.
15th-Mar-2014 06:50 pm (UTC)
The track itself (index 01 in CD terms) starts at 45000, if you add the pregap, it should start at 45000-150=44850, so other tracks are unaffected, there is no overlapping and the .gdi is correct.
15th-Mar-2014 07:33 pm (UTC)
So many things wrong with that statement... No, track 3 starts at 45000 with index 0, which makes it a 2s pause, thus a pre-gap. The actual data start at 45150 and you can verify that by inspecting sector header in raw dump. Better yet, go read ECMA-130 and stop spouting this nonsense...
16th-Mar-2014 04:14 am (UTC)
Can we play TOSEC dumps?
16th-Mar-2014 08:47 am (UTC)
TOSEC and Dumpcast. Or your own dumps. Or dumps done on PC drive as long as it's not the redump's / trurip's braindead hackery.
This also includes CD images in CDI format for homebrew, and ISO as well though obviously that's not self-bootable. Can be used as data carrier though for homebrew apps.
16th-Mar-2014 11:41 pm (UTC) - Fantastic News
Congrats on your work buddy, seems I picked tan interesting time to start reading into the DC scene again!

Would love to buy at least one if I can! I'll keep a close eye and on your posts in case I'm lucky enough :)
18th-Mar-2014 11:37 pm (UTC) - Buying a GDEMU
Outsider checking in, I will definitely buy one!
22nd-Mar-2014 08:49 pm (UTC) - beautiful!
i'll take 2!!!! SRSLY 2.
25th-Mar-2014 11:05 am (UTC)
Hello,

Very very good job
I too am interested to buy a device.

goodbye
25th-Mar-2014 11:57 pm (UTC) - GD Emu
I'm down for one, when I tell me friends I recon they will be too
30th-Mar-2014 12:56 am (UTC) - Count me in...
... Depending on price and ease of installation, anyway.
31st-Mar-2014 07:31 pm (UTC) - Manufacturing in China
Evening mate, been following your project with interest for a while. This used to be the holy grail back in my scene days and its such a buzz seeing an old dream come true.

Just dropping you a line to say that if you need any help getting larger quantities manufactured in China then I'd be more than happy to help you out by throwing some resources your way. I'm also willing to help you source the financial backing but given this day and age you'd honestly be better off crowd sourcing it.

You can drop me a line via here if interested.

Either way, kudos on the graft - a job well done :)
31st-Mar-2014 08:06 pm (UTC) - Slowpoke here
I'm in. I'd buy one, or even a few. :)
3rd-Apr-2014 11:23 am (UTC) - I want one!
That nice, I want one to continue my Shenmue translation project... !
4th-Apr-2014 12:34 am (UTC) - Awesome! I'll totally buy one!
I saw on your page that pre-orders are already closed, but as soon as they are available, I will get one.

Any idea if/when preorders will reopen?

Edited at 2014-04-04 12:43 am (UTC)
19th-Aug-2014 03:26 pm (UTC) - GDROM Explorer: version 1.6.2 out
User japanese_cake referenced to your post from GDROM Explorer: version 1.6.2 out saying: [...] errors that need to be fixed. For those who have read Deunan's post regarding bad GDI dumps [...]
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