Where is the scratch? or where is sector 500,000?

vbimport

#1

Hi,
Not sure where to ask this, to this make me beginner. :slight_smile:

Is there a way to find physical location on the DVD based on sector number?
Now I am not talking pinpoint accuracy, but postage stamp area is good enough.

I had badly scratched DVD-Video that failed ripping at one point even after 100s retries and the general cleaning I do with toothpaste that helped me in the past. The other day I just could not read the DVD-Video, on 2 different drives, etc. I was using DVD Decrypter that report the failure. It would have helped me a lot if I could concentrate on small area for further cleaning.

Now, I know there are different media, DVD media, pressed and burnt, SL and DL, +R and -R, So it is possible? Where is sector zero anyway?


#2

I have seen a sector map before (a very aproxamate one). Maybe someone more farmiliar might be able to provide more info on that, but my experience was, they go in rings, and it can be very difficult to find the offending area, even with a sector map. Have you considered alternative methods of repairing the disk? I discussed this a while back (here if I am not mistaken) and here are two ideas. First is a product called plexus. I use this product all the time and love it. In a thread a while back, we were discussing polishing etc. and this one guy was using sandpaper to test disks (sand and then try to polish and read). So I recomended plexus and at first he was really disapointed with his testing (no visual improvment), but when he actually tried it on a disk that would not read (and wasn’t intentionally damaged), it helped. You couldn’t see a visable change (much), but it helps. This product is wax based product that fills the scratches. I know most of these are crap (especially the allstop ones you get in stores locally), but this stuff really works. It is not a magic cureall, but it makes about 90 percent of unreadable disks readable (for me anyway). Even when plexus didn’t work, and polishing with abrasives didn’t work, polishing with abrasives and then plexus worked. It’s this
http://www.plexusplasticcleaner.com/about.html
Your easiest bet to get it is any local motercycle shop. They use it on the windshilds and fiber glass pannels to cover scratches. I paid 7$ for an aerosol can (kind of a small can but I have used it on hundreds of disks and it is still half full). I don’t know how I ever did without this stuff.
Another product that was dissussed was novus (an abrasive polishing compound set). while I have not used it, based on what was said and the description of it, it looks like an exelent product to try. I have tried many abrasive products (tooth paste, metal polishes, automotive buffing compounds (the fine ones), various cd/dvd repair kits that are all shit and the plexus is very well worth having (for use prior to or after polishing) and the novus, while I have not used it, looked very promising.
Just trying to give you some ideas (I know how frustrating spending an hour trying to polish with toothpaste or metal cleaner can be). I just wish I could find a decent electric polishing unit that is affordable (not the expensive comercial ones). I am currentlly using this
http://www.compusa.com/products/product_info.asp?product_code=304709&pfp=BROWSE
With my own polishing compounds. It does ok sometimes but doesn’t get to the edge of the disk and the replacment pads so you can try diffrent polishing compounds might as well come with a free jar of vaseline!!! I would like to try it with some novus, but the plexus works well enough (and I haven’t had any must be recovered disks with important data and no backup), so I just haven’t got around to trying it.


#3

Thanks for the reply.

I finally managed to read the DVD after 100s retries, but I know I spent too much time polishing with toothpaste all of the disc, instead of smaller area. I know to use radial movements from hub to edge, so it is just too much work. Had I known somehow where is the bad spot, by area size of a postage stamp or a slice say 1/8 of the disc, it would have saved me time.

Need to find out where sector zero start, if there is some visible physical mark on the disc :slight_smile:


#4

You can keep hunting for the offending scratch, or look for a beter method. I would sugest a beter method, but thats just me.


#5

The below table is based on normal DVD specs for single layer and dual layer. I rounded the logical block address (LBA) ie… sector number. The radius is from the center of the disc


  RADIUS      	   SINGLE   	    DUAL
24.00mm = LBA	          0	          0
25.00mm = LBA	     40,000	     37,000
26.00mm = LBA	     82,000	     75,000
27.00mm = LBA	    126,000	    114,000
28.00mm = LBA	    171,000	    155,000
29.00mm = LBA	    218,000	    198,000
30.00mm = LBA	    267,000	    242,000
31.00mm = LBA	    317,000	    288,000
32.00mm = LBA	    368,000	    335,000
33.00mm = LBA	    422,000	    384,000
34.00mm = LBA	    477,000	    434,000
35.00mm = LBA	    534,000	    485,000
36.00mm = LBA	    592,000	    538,000
37.00mm = LBA	    652,000	    593,000
38.00mm = LBA	    714,000	    649,000
39.00mm = LBA	    777,000	    706,000
40.00mm = LBA	    842,000	    766,000
41.00mm = LBA	    909,000	    826,000
42.00mm = LBA	    977,000	    888,000
43.00mm = LBA	  1,047,000	    952,000
44.00mm = LBA	  1,119,000	  1,017,000
45.00mm = LBA	  1,192,000	  1,083,000
46.00mm = LBA	  1,267,000	  1,151,000
47.00mm = LBA	  1,343,000	  1,221,000
48.00mm = LBA	  1,421,000	  1,292,000
49.00mm = LBA	  1,501,000	  1,364,000
50.00mm = LBA	  1,583,000	  1,438,000
51.00mm = LBA	  1,666,000	  1,514,000
52.00mm = LBA	  1,750,000	  1,591,000
53.00mm = LBA	  1,837,000	  1,669,000
54.00mm = LBA	  1,925,000	  1,749,000
55.00mm = LBA	  2,014,000	  1,831,000
56.00mm = LBA	  2,106,000	  1,914,000
57.00mm = LBA	  2,199,000	  1,998,000
58.00mm = LBA	  2,293,000	  2,084,000
59.00mm = LBA	  2,389,000	  2,172,000

Hope someone finds this useful.


#6

RichMan you got the same table for CDs?


#7

It’s not as straight forward with CD since the spec is much ‘looser’ with track pitch and linear velocity. And then there’s multisession to deal with. All of this changes the location of the LBA. But, I will give another table that shows the general location for a single session ROM CD (maybe tomorrow if I have time to do the math).