Converting Stream preservation files to PSI / TD0

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AmazingA
Posts: 5
Joined: Sat Sep 25, 2021 11:23 pm

Converting Stream preservation files to PSI / TD0

Post by AmazingA »

Hi all,

I'm quite new to dumping PC games and creating working images out of my copy protected games.

Unfortunately, I didn't find any tutorial on how to do that, but rather some forum threads, such as the following:

https://www.vogons.org/viewtopic.php?f= ... 60#p405910

Creating a PFI file out of the stream works just fine.

However, I am already stuck with the next step:
The command "pfi <game>.pfi -p analyse" does not work in the downloadable versions of PCE. I assume that this command is somehow deprecated.
When I perform the command, I get the following error: "pfi: unknown operation (analyse)".
Therefore, I can only "guess" the parameters (frequency, double-step, MFM) for creating a PRI file and afterwards a PSI file.
And this does not (always) work, of course.

Can you help me out on this issue?
(I couldn't find older versions of PCE, the oldest is from 2019 with the same error.)

And 2nd question:
How can I get TD0 images work with 86Box?
(I have converted one PSI file game to TD0 and it worked perfectly with 86Box. But another game didn't even though the PSI file worked on PCE.)

Thank you guys for your support.

With best regards
brightcaster
Posts: 477
Joined: Fri Nov 08, 2013 10:48 pm

Re: Converting Stream preservation files to PSI / TD0

Post by brightcaster »

I can't tell you much about PFI because I'm not familiar with it. But TD0 was and still is a proprietary file format. All converters are based on reverse engineering and may be imperfect to a certain degree! (There has been a short description of the TD0 file format with version 1.05 of teledisk.)

Also the PSI format can handle some protection schemes (such as "weak and fuzzy" bits for example) that TD0 cannot map.

So if the PSI is working and the TD0 fails, it could be an imperfect converter as well as a copy protection that is not supported by TD0 images.

David
SomeGuy
Posts: 348
Joined: Wed Feb 18, 2015 8:18 pm

Re: Converting Stream preservation files to PSI / TD0

Post by SomeGuy »

Well, here is an example of converting a DSDD MFM disk to IMG format:

pfi track00.0.raw disk1.pfi
pfi disk1.pfi -R 1 -r 500000 -p decode pri disk1.pri
pri disk1.pri -p decode mfm disk1.psi -f -v
psi disk1.psi disk1.img
psi disk1.psi -L > disk1.txt

First you just convert directly to a PCE Flux Image - this contains flux-level data just like the Kryoflux preservation stream.

Then convert to PRI format. This is decoded MFM/FM/GCR track data, but not yet broken down in to sectors.

Data rate is typically:
500000 for low-density MFM
600000 for low-density MFM in a 1.2mb drive
1000000 for high-density MFM
The rate is half of that when using FM.

Then convert to PSI, the PCE sector format. This format is designed to hold absurd layouts, as might be found in copy protection, but it does not preserve things like overlapping sectors, so many copy protected images may work, but some won't.

This step can get complicated with weird copy protections - for example, the PSI format supports the ability to tack on extra data after the end of a sector, as might be seen in an FDC "diagnostic read" operation used by many protections, but this must be specified manually.

You can convert to ImageDisk or TeleDisk format simply by specifying .IMD or .TD0 in the output filename instead of .IMG.

Note that neither ImageDisk nor TeleDisk were designed to handle copy protection. They were simply designed to read non IBM PC disks. What that means is that only very simplistic copy protections - such as a misnumbered sector or an odd sized sector - will work in these formats.
AmazingA
Posts: 5
Joined: Sat Sep 25, 2021 11:23 pm

Re: Converting Stream preservation files to PSI / TD0

Post by AmazingA »

Sorry, I was very busy lately and saw your posts right now.

Thank you both for your answers, especially for the little tutorial and the right frequency parameters for the different disk formats.
That is what I was looking for. I will give it a try for my copy-protected games.

With best regards
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