26 (edited by pnkiller78 2008-02-25 01:42:31)

Yeah, I agree with you, apparently httpd-ack doesn't dump pregap of the data tracks, that's why track 2 have 150 sectors less, and track 20 too. In the case of track 2 it's easy to fix because it's readable by EAC and PC drives, but in the other case we must guess.

I have not moved any data, I generated 'em using hex-editor (150 sectors filled with zeros), the dump from the last data track (track 21) start with info from files, not pause... and the end of track 20 ends with audio, I'm assuming that what it's missing is the track 21 pregap, so I generate it and inserted at the end of the previous track (track 20).

pnkiller78 wrote:

I have not moved any data, I generated 'em using hex-editor (150 sectors filled with zeros), the dump from the last data track (track 21) start with info from files, not pause... and the end of track 20 ends with audio, I'm assuming that what it's missing is the track 21 pregap, so I generate it and inserted at the end of the previous track (track 20).

I doubt 3rd data track pregap has just zeroes (because it's data track, not audio, it should have at least sync and header). Also pregap should be added to the beginning of data track, not to the end of previous audio track.

Oh, I see, sad
What do you think we could do by now?
Is there a way do dump the pregap for that track?

I am not sure if we can dump it (with this tool), but I think there is no data there except for the sync, header (perhaps also EDC & ECC) — we need to ask Vigi.

30 (edited by pnkiller78 2008-02-25 07:02:19)

Ok, I made this discovery...
In the url in httpd-ack for dumping the last audio track there's a parameter that can be modified to force the daemon to dump the entire track including the pregap

this is the original url
http://192.168.1.253/track04.raw?ipbintoc0_session02_p4096_cdxa0_sector_size2352_gap150_dma1_sector_read16_sub0_abort1_retry5
this is the modified url
http://192.168.1.253/track04.raw?ipbintoc0_session02_p4096_cdxa0_sector_size2352_gap0_dma1_sector_read16_sub0_abort1_retry5

This way the resulting last audio track contains the pregap for the last data track appended to its end.
Analyzing the data in this last 150 sectors, I found that indeed they are empty data sectors, that it's, sectors with no data, just the sectors with the appropriate control fields (Sync, header, EDC, etc), but there's something different in every disc, the first few sectors (5-30 sectors) are shifted by the offset that appear on the audio tracks and the data is not zeros, it's garbage like the one that appears scrambled while calculating disc offsets in ISOBuster sector viewer. Also, I cannot get the same garbage data by reading the track again, if I read the track again, the garbage appear on the same place, but with differente numbers, after the garbage data ends, the zero data sectors appear exactly in the same position with the same control fields every time.
By example, dumping track 20 of Sega Rally, it showed 5 sectors or garbage data in the last data track pregap, after that 145 secotrs were consistent if dumped over and over again.
With Slave Zero, it showed 29 sectors with corrupted info, again with every read, the garbage changed, the remaining 121 sectors of the pregap were the same.

If this pregap it's added to the begging of the last data track, the gdi adjusted properly using the proper values for the sizes of the audio track made the game playable on nullDC.

Also, I made an experiment, if I generate the pregap using zeros, append it to the last data track at the beginning and then fix the sectors using CDMage, the sectors that stayed consistent on the dumped pregaps are the same, that's mean the 145 sectors for Sega Rally and the 121 sector of Slave Zero match their values with the corresponding sectors generated and rebuilded with CDMage.

So, I think that the pregap, it's in fact just zero data in data form1 sectors, that it can be generated, appended to the beginning of the last data track, fixed or rebuilded with CDMage.

What do you think?

Can you please upload two pregap dumps from the same game?

Dremora wrote:

Can you please upload two pregap dumps from the same game?

Here, this is the pregap from Sega Rally 2, they got 37 sectors that don't match in each dump, the data change everytime until offset 0x153F0.

It seems I can't download files from this filehosting. Can you please upload it somewhere else?

I send it by e-mail... 15 kb after all smile

35 (edited by pnkiller78 2008-02-26 15:05:33)

Dremora wrote:

It seems I can't download files from this filehosting. Can you please upload it somewhere else?

Hi, did you receive the files? What you think about the behavior of those gaps?
Also, I was thinking in completely ignoring that data pregap thing, in fact, the other data tracks doesn't have their corresponding pregap appended at the beginning, the games with just a data track in the second session doesn't have their pregap too, in fact all of our dumps (as far as I know) doesn't have data pregaps appended to the beginning.
I think that in the gdi format: sectors existence is not performed, I mean it doesn't check that those 150 sectors for pregap exist in the file being readed, the script for generating the gdi file could be adjusted to sum 150 to stating position of the last data track.
So, the only extra extraordinary step that we would have to take while dumping these DC discs (the one with audio tracks), would be
* Fixed track 2 according to EAC
* Added the pregap to the track 4

What do you think?

Yes, thanks, I've received the files. The gaps are really strange, but I want to compare them with gaps from Vigi's dump.

pnkiller78 wrote:

in fact all of our dumps (as far as I know) doesn't have data pregaps appended to the beginning.

Only first tracks of the session are missing pregaps because it's impossible to read them on many drives. But PCE CD data tracks are usually located not in the beginning of the disc, and they all have pregaps in DB.

Dremora wrote:

but I want to compare them with gaps from Vigi's dump.

Which track from which game would you like?

@pnkiller:

When I used the lite-on to dump these gdroms I could see where the audio started because of scrambled data.. also, the data track in the high density area contains information about the track sizes.. you can view the toc of a dump with a tool called gdlister.. just get the toolkit from this page:  http://homepage.ntlworld.com/menace-59/ … oolkit.rar

Also, I noticed StateS is mentioned on this page.. http://homepage.ntlworld.com/menace-59/gd-rom_stuff/ perhaps he could tell us if it's him or just a guy with the same name? tongue

Vigi wrote:

Which track from which game would you like?

Mortal Kombat Gold, track 53, first 150 sectors. TIA smile

Dremora wrote:
Vigi wrote:

Which track from which game would you like?

Mortal Kombat Gold, track 53, first 150 sectors. TIA smile

I borrowed this game and I deleted the dump, so I don't have it anymore hmm

but I still have another game with audio tracks (who wants to be a millionaire) and plextor + escape eject also works fine for gdroms (just tested) yikes:O

Does it have 3rd data track?