Unofficial Deunan's GDEMU Thread

Discussion in 'Sega Dreamcast Development and Research' started by duskdawn, Jul 8, 2015.

  1. Tarnish

    Tarnish Member

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    Hello everyone, been a lurker for a few years who registered a few years back. Got a clone GDEMU and thought I'd share some things I ran into so far.

    1. I bought a 256 GB Kingston card with the intention of fitting basically the entire NTSC-U library + the PAL exclusives + some NTSC-J games (I wanted to get all the games on a single card because I wanted a 'get it done once and never bother with it again' solution, and I didn't want to get multiple cards that I have to swap back and forth based on what game I want to play). So I bought the following card which so far seems to work perfectly.
    MM260645.jpg
    2. In order to fit all of the games, I used the GDIrebuild tool. So far these are the games I noticed the rebuild causes issues:
    - TruRip NTSC-U Worms Armageddon: game instantly freezes upon startup.
    - TruRip NTSC-U Sega Rally 2: game boots fine, but when loading the Mountain stage 1, the game crashes and goes back to the GDmenu.
    - TruRip NTSC-U Resident Evil 2 (both discs): game crashes after the 'Game contains explicit gore' screen.
    - TruRip NTSC-U Draconus: game crashes upon startup.
    - TruRip NTSC-U Dragon Riders: game boots, but goes wacko as the videos don't play in order and the subtitles/choice selection doesn't appear on screen, so it becomes unplayable.
    - TruRip NTSC-U Hidden & Dangerous: game freezes at the loading screen after the first 'Press Start button' prompt.
    - TruRip NTSC-U Max Steel - Covert Missions: game instantly freezes upon startup.
    - TruRip NTSC-U Nightmare Creatures II: throws an error message after the first 'Press Start button' prompt screen and freezes there.
    - TruRip NTSC-U Starlancer: freezes upon start-up.
    - TruRip NTSC-U Tomb Raider - The Last Revelation: freezes upon start-up.
    - TruRip NTSC-U Tomb Raider Chronicles: freezes upon start-up.
    - TruRip NTSC-U Urban Chaos: crashhes upon start-up.
    - TruRip NTSC-U Wild Metal: freezes after Rockstar logo.
    3. TruRip NTSC-U Sega Rally 2 (even the original/unshrunk image) quite often freezes on the SEGA/WinCE logo, but if I set the GDmenu to skip the start-up and SEGA logo, it boots up fine.

    I'll keep updating this post as I find more issues.
     
    Last edited: Apr 11, 2019
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  2. Anthony817

    Anthony817 Familiar Face

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    Welcome, thanks for posting your findings. Don't I know you from somewhere? Your name is really familiar. Weren't you a member over at TIZ?
     
  3. Tarnish

    Tarnish Member

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    I only posted like half a dozen comments on TIZ. You probably remember my name from DC-Talk. I was the guy with the picture of the PS4 stick mod showing the wear and tear over time.
     
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  4. krisk77

    krisk77 Peppy Member

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  5. Anthony817

    Anthony817 Familiar Face

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    Oh yeah that was it!
     
  6. Tarnish

    Tarnish Member

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    I only chose that card because it was the cheapest I could find in the 256 GB size.

    I can't comment on other Micro SD cards, but so far all of the issues I ran into seems to be due to rebuilt images, as when I put the untouched 1,1 GB images on the same card, the issues are no longer present.
     
    Last edited: Apr 12, 2019
  7. Tarnish

    Tarnish Member

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    So I recently found out about GDIshrink which has higher compatibility (only 2 games don't work with it). With that in mind, I switched to that instead of the GDIrebuild.

    However, apparently the shrinking also causes issues with some games sadly, mostly the same ones the GDIrebuild caused issues.
    - TruRip NTSC-U Sega Rally 2: game boots fine, but when loading the Mountain stage 1, the game crashes and goes back to the GDmenu.
    - TruRip NTSC-U Tomb Raider - The Last Revelation: freezes upon start-up.
    - TruRip NTSC-U Tomb Raider Chronicles: freezes upon start-up.
    - TruRip NTSC-U Urban Chaos: throws up some kind of error message regarding text files.
    - TruRip NTSC-U Wild Metal: freezes after Rockstar logo.
     
  8. -=FamilyGuy=-

    -=FamilyGuy=- Site Supporter 2049

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    You shouldn't use TruRip with GDEMU to begin with.

    Try sourcing those games from other sources.

    I might try to improve gdishrink at one point, but for now it works good enough for most games and I don't really have the time to code a corner case for each and every weird/insane data layout that a developer used.
     
  9. Teddy Rogers

    Teddy Rogers Spirited Member

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    I have never come across any problems with TruRip dumps and GDEMU. Correct me if wrong, I recall a post where someone had tested all TruRip dumps and found only one that did not work - NBA.

    What is the issue with TruRip?

    Ted.
     
  10. -=FamilyGuy=-

    -=FamilyGuy=- Site Supporter 2049

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    Maybe I'm confusing it with redump? I'm not well versed in the dumping scene.
    What you want is dumps that match with TOSEC.
     
  11. Teddy Rogers

    Teddy Rogers Spirited Member

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    I think it likely to be Redump. I have never used Redump myself so I cannot comment from experience. TruRip and TOSEC both work fine for me...

    Ted.
     
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  12. psydefx

    psydefx Peppy Member

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    its redump. trurip are same as tosec just renamed differently
     
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  13. Tarnish

    Tarnish Member

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    That's funny, because there's a note in the 'shrinkall.sh' file saying "NOTE: If you have the REDUMP game set, they add some non-standard track data to their gdi files that may or may not work correctly. TOSEC or TruRip are preferred." =P
     
  14. -=FamilyGuy=-

    -=FamilyGuy=- Site Supporter 2049

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    Yeah my bad, I unconsciously associated not-TOSEC with bad.

    Mea Maxima Culpa!

    The rest of my post stands though.

    PS : I didn't write a sh script to shrink a bunch of games. Ensure that the provided gditools.py file is up to date for optimal compatibility.
     
  15. Tarnish

    Tarnish Member

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  16. -=FamilyGuy=-

    -=FamilyGuy=- Site Supporter 2049

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  17. darcagn

    darcagn Site Supporter 2013, Site Supporter 2014

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    To clarify on the dumping, you're likely to see dumps labeled, Dumpcast, TOSEC, TruRip, or Redump.

    - Dumpcast was the first effort to dump DC games, founded by myself and 2 other members of DCEmulation and Underground-Gamer. We dumped in old flawed GDI format + ISO2048 + RAW audio using Dreamcast consoles, but the dumping software was unreliable and these dumps no longer exist anywhere.
    - TOSEC, a long existing dumping group, then started Dreamcast dumping and the two groups worked together. TOSEC members provided newly written, better software and prior dumping experience, and Dumpcast simply became a forum for dumpers to collaborate (https://dcemulation.org/dumpcast/). TOSEC also dumps using Dreamcast consoles. These were the new GDI format + BIN2352 + RAW audio, you will sometimes see these labelled as "Dumpcast" on torrent sites, but those are TOSEC torrents. TOSEC requires all discs to be dumped twice by two different people so this set has never as far as I am aware had a bad dump included. If you can, get the TOSEC set!
    - Redump is a newer dumping group that started dumping around the same time TOSEC did, however they use PC drives to dump. Their dumps differ from TOSEC dumps because off the different audio offsets between drives and because their specific PC drives can read some (completely irrelevant) data from the discs that a Dreamcast console can't. However, this data is entirely predictable and so both formats can be converted back and forth with software and know-how. Historically, they have lagged behind in number of games in their set when compared to TOSEC, but in the past couple years they have surged in dumpers and have about the same amount of dumps as TOSEC, however TOSEC has more twice-dumped, verified discs. The problem with Redump dumps is that they shoehorned their different dump format data into the GDI layout format, so ODEs and emulators may have problems with some of these dumps. Fortunately, Redump has just recently abandoned GDI and adopted a new custom CUE format for their DC dumps, but none of the ODEs currently support it and emulator support is spotty.
    - TruRip was a new dumping group that had some overlap of members from TOSEC, and they used data from both TOSEC and Redump sets so there's a mix of both formats (you know it'll be like Redump format if the filename has "_oc" in it (for 'offset-corrected'), but I don't think these OC dumps are commonly shared online anyway). TruRip did not require 2x dumps so that set contains some more ultra rare discs that have only been dumped once, like unreleased games. It also includes MIL-CD/indie software, fan made hacks and translations, etc. However this set has not been updated in many years, so it's also missing stuff that is now in TOSEC.


    So in short, grab the latest TOSEC set (December 2018 as of this writing)* and if there's anything else you want, seek it specifically from other sets. TOSEC has 100% NTSC-U and PAL games, at worst the only thing missing from western DC library is ultra rare demo discs or obscure language variants and the other sets don't have those either. TOSEC also has all the NTSC-J games an English speaker is likely to want as well.


    * The latest set is not easily found on the internet, but if anyone has stable hosting that will last and not just get taken down in days, I could perhaps assist you in seeing to it that the latest set ends up there... PM me... ;)
     
  18. Tarnish

    Tarnish Member

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    Thanks for the info. The thing I'm curious about now is why do some games have multiple GDIs in the same dump? And I don't mean Midway's re-releases or regular and limited editions, I mean for example why does the NTSC-U Shenmue's 3rd disc have multiple GDIs uploaded? What's the difference between those when they are labeled to be the same version of the game?
     
  19. darcagn

    darcagn Site Supporter 2013, Site Supporter 2014

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    Sure, I can explain that, those are called "ringcode variants" or "audio variants."

    It has to do with audio track offsets, and is a challenge for any group dumping media with audio tracks (DC games, PS games, music CDs, etc.). The data tracks in those dumps should be 100% the same, byte-for-byte.

    The audio tracks however, when manufactured, will have an number of zeros padded to the beginning of the file, and this number of zeros is called the "write offset." Discs manufactured in different facilities for example might have the same exact source audio go to manufacturing but come out differently because the different batches will have had different write offsets, even though the only difference is a few bytes of zeros at the beginning of the file. This actually can make extremely common games difficult to verify by having 2 different people dumping 2 different discs, because they were often made in many batches, and you have to hope to get two discs from the same batch. They can be identified as being part of the same batch by looking at the ringcode in the shiny center part of the disc (those Shenmue disc 3 variants, for example, start with "1S" and "2S" on their ringcode printed on the disc's center, that's why you'll see that in the TOSEC filename).

    You might have noticed that this doesn't apply to PAL games, as all PAL games were manufactured in the same facility (that's why they all say EMI CD HOLLAND on them). Japanese and North American dumps have ringcode variants though.

    In addition, different disc drives also read discs differently, so you can have 2 people with the same exact disc from the same exact batch but have different disc drives that have a different "read offset" produce different files when dumping discs. Luckily, this is not a problem for TOSEC Dreamcast, because we dump using Dreamcasts and all Dreamcasts (regardless of whether it's a Samsung or Yamaha drive) have the same read offset, so we simply ignore the read offset.

    However, for Redump, and other dumping groups which use PC disc drives to dump, all which have different read offsets, this is a challenge, so they use special software that detects and corrects both read and write offsets to a standard value. So you will not see ringcode variants in Redump, because they truncate zeros from their dump files to correct it.

    When building an SD card for GDEmu just pick one disc from the ringcode variants, definitely don't pick them all, it's a waste of SD card space. But TOSEC chooses to index all variants instead of picking just one because it is supposed to be possible to dump your own GD-ROMs and verify them against TOSEC. For example, if I am selling a game, I would dump it and make sure it matches TOSEC's database to be 100% sure every sector is free of read errors and then I can advertise that on the listing to make it more appealing. :)
     
  20. megavolt85

    megavolt85 Peppy Member

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    @darcagn why dumpers don't use pair GD-ROM drive+PC?
    why data tracks contain garbage (ECC/EDC)?
     

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