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sscotts
November 4th, 2000, 21:08
Hi all!
I am desperate about rescuing my corrupt cd-r which contain precious data. Any suggestion on how to go about on this one. Thanks.

sscotts

cronos
November 5th, 2000, 05:21
You really dont give enough details on whats happened:

Did the CD appear to write and then you can't access it ? (In which case it could be completely gone)

Did it just mess up when you were adding another session to it ?

Can you see anything on it ? Directories, etc ?

Have you tried it in other drives ?

Does the drive appear to read anything ? Or does it get spit out by the drive as soon as you put it in ?

What have you tried to read it ? Tried reading it from dos ?

sscotts
November 5th, 2000, 12:12
Thanks for replying to this.

The problem start when I accidently format the disc using DirectCD. Well, It was just starting to format when I intervened.

Now, Windows Explorer shows that there is some space "used" but did show any icons like .doc or .jif or .txt

If I use another cd-rom drive, It will say "Drive is not ready" "abort or Retry"
Thanks again.

cronos
November 5th, 2000, 17:50
>The problem start when I accidently format the disc using DirectCD. Well, It was just starting to format when I intervened.

Hmm, so this is a CDRW then ? Partially reformatted...... oh dear.

> Now, Windows Explorer shows that there is some space "used" but did show any icons like .doc or .jif or .txt

OK, so at least the drive isnt just spitting it straight out.

> If I use another cd-rom drive, It will say "Drive is not ready" "abort or Retry"
Thanks again.

Well, most CD drives won't accept Direct CD's packet discs anyway.

Now, recovery isnt going to be easy. Let me say that at the start. To recover stuff from this disc you are going to have to put in a lot of time and a lot of effort. Its the same with any kind of disc recovery operation - hd or cd. You have to weigh up the cost of doing it against the cost of the data that you would get back.

My first approach, which is prior to bringing in the heavy duty stuff (which starts with some good programming exercises) would be to try some real disc reading software. The blind-read kind of software that tends to be available on sites like http://www.gamecopyworld.com/ Basically you want to try and create an image file on disc of what you have on that cd. The reformat (depending on which option you chose - full format or quick format ?) if it was quick format would have been a toc wipe, and so you will still have most of the data there, you just need to reconstuct the toc (easier said than done, but a cd toc is normally consecutive rather than randomised like a hd toc, unless its been read/written to a lot). If its a full format you might have lost some files but some of the toc might be ok. Anyway, get yourself a blind reader and sit back and read the disc (presuming you cd writer will do it, if not then its going to be harder).

OK, now you should have a cd image with any luck, a blind read of the cd contents. Given this you should now be in a position to start file recovery. You can get programs which will read the image file directly, but I suspect most will choke on a screwed image, so its going to be a manual data-extraction exercise from here.

I need to know several things at this point - 1/ did you manage a blind read, do you have an image file of some kind ? 2/ whats it looking like, how did the operation go ? 3/ just how good are you at being able to write the odd program to peer into this file ? 4/ what kind of data is in there ? text/compressed ? 5/ Just how valuable is your data and how far are you prepared to go ?

cronos
November 5th, 2000, 18:36
Following my earlier post I would add that it helps to read up on these things, and so here a few links:

http://www.emediapro.net/MayEM/mcmurdie5.html
http://www.adaptec.com/products/faqs/udfreaders.html
http://www.octave.com/0/en/library/daotao.html

And quotes:

* If you have a CD-RW disc originally formatted with DirectCD 1.0x, DirectCD 2.0x will continue to write to that disc in variable-length packets, so you cannot randomly erase and recover space on it. In order to prepare the disc for random erase, you need to erase it completely and reformat it with DirectCD 2.0.

So I presume that you will have use Fixed-length packets (random erase) which will hopefully be in our favour

Each time data is added incrementally to a CD, the laser must power up and power down, and as a result, useless blocks of data may be recorded to disk. Link Blocks are simply the blocks before and after user data that may contain this useless data. A single instance of written user data along with its associated Link Blocks is called a packet. Additionally, a special set of blocks called Run-in and Run-out blocks are written. These blocks allow the CD recorder's clock to get in sync with the recording at hand, and for interleaved data to play out.

There are some problems with packet writing, mostly due to the inability of older CDROM drives to deal with the gaps between packets. CDROM drives can become confused if they read into the gap, a problem complicated by read-ahead optimizations on some models.

Now, for the final link, which may be a get out of jail link for you if this software works (I haven't tried it personally):
http://www.cdrom-prod.com/software.html
allows you to test, examine and recover data from CD, CD-R and CD-RW discs. This includes support for discs written using Adaptec DirectCD and CeQuadrat PacketCD as well as other packet-writing programs. It bypasses Windows and other CD software installed on your computer to allow complete freedom to examine nearly any CD, including Macintosh and audio discs.

sscotts
November 6th, 2000, 19:26
Cronos,
I would sincerely like to thank you for all this help. This would be my "big" project and yes, it is something valuable. My late pet's pic is among them. Again, thank you.

sscotts