[plug] Getting data off a damaged DVD

[philC]

Senectus et al

dd is the best lower level copier I know. Any lower and you probably have to 
over ride the cd firmware driver, which itself has several layers of error 
control ( as every cd will have some errors but crc's and the like make them 
not critical).
dd gracfully skips after (several?) tries at bad files, much as cp seems to 
do but much quicker- so much so I scrapped the trial cp of cd before it 
finished. Much better than windows copy which spits the dummy after 
encountering first error. Interestingly the trial dd iso file size was 
smaller than the copied contents using cp which hadn't completed it task.

use dd to copy to a file, mount it as type iso and off you go. However if 
files are corrupted you'll probably still only have garbage. The key is 
knowing whether it is or is not garbage which leads me to my problem:

I have many backup snapshot cd's which I want to consolidate back into one 
lot on the hard drive without duplicates. Some of them came back from Middle 
East with sand btween them. What I want to do is read the cd directory to 
get a file list, then visit each file in the directory list and copy across 
if not already in the consolidated target - or skip if file read error. This 
needs some sort of timeout control. However Bash shell is not very good at 
this. Any suggestions? Possible pseudo code follows.
    call cd read script on a per file basis and run in background with &
    sleep for a timeout period
    check background script still running
        if running kill it (presuming its having a read problem) and mark as 
garbage
    loop to next file

Doing it this was is you are less likely to have copied files which you may 
think are intact but because of the cd errors are only garbage.

PhilC


----- Original Message ----- 
From: "Senectus ." <senectus at gmail.com>
To: <plug at plug.org.au>
Sent: Friday, June 30, 2006 5:48 PM
Subject: [plug] Getting data off a damaged DVD


>I am having issue's getting data off a DVD disk that appears to be
> damaged (cant see any physical scratches.)
>
> Is there some tool that will help me extract what I can off it?
>
> -- 
> www.modmeup.net
> Ubuntu Dapper 6.06
> The less you know, the more you believe. - Bono
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