[mythtv-users] DVD ISO playback problems: Invalid IFO

Michael T. Dean mtdean at thirdcontact.com
Thu Jan 10 00:40:44 UTC 2008

On 01/09/2008 07:21 PM, Seth Daniel wrote:
> On Wed, Jan 09, 2008 at 07:14:00PM -0500, Michael T. Dean wrote:
> [...snip...]
>> /me wonders why distros still use dd_rescue instead of ddrescue (and, if 
>> installing dd_rescue, why they don't install dd_rhelp).
> Well, Ubuntu (I'm running Hardy) has a package named 'ddrescue' which
> installs a program named 'dd_rescue'.  It would appear that the binary
> is the Garloff version.  
> $ dd_rescue
> dd_rescue: (fatal): both input and output have to be specified!
> dd_rescue Version 1.13, garloff at suse.de, GNU GPL
> ($Id: dd_rescue.c,v 1.55 2007/03/18 14:29:10 garloff Exp $)
> dd_rescue copies data from one file (or block device) to another.
> [...snip...]

Yep.  Perhaps the MythBuntu guys would have some insight into why Ubuntu 
uses dd_rescue (or enough pull to recommend a change--either including 
dd_rhelp or, better, using ddrescue).

> Works fine for me, but I didn't quite follow all the ins and outs of
> your e-mail.  I had never heard of dd_rhelp.

 From the dd_rhelp page:
This makes dd_rescue the best tool for recovering hard drive having bad 
sectors. ...

But using it is quite time consuming. This is where dd_rhelp come to help.

In short, it'll use dd_rescue on your entire disc, but will try to 
gather the maximum valid data before trying for ages on badsectors. So 
if you leave dd_rhelp work for infinite time, it'll have the same effect 
as a simple dd_rescue. But because you might not have this infinite time 
(this could indeed take really long in some cases... ), dd_rhelp will 
jump over bad sectors and rescue valid data. In the long run, it'll 
parse all your device with dd_rescue. You can Ctrl-C it whenever you 
want, and rerun-it at will, it'll resume it's job as it depends on the 
log files dd_rescue creates.

So, basically, it explicitly jumps over bad blocks (which are slow to 
read) until it's gotten all of the good data (which is fast to read) 
first.  It also allows you to stop/resume at any time.  Once it gets all 
the good data, if you continue to let it run, it will continue to work 
on the bad blocks.  GNU ddrescue does the same, but doesn't rely on a 
shell script (dd_rhelp) for the added functionality.  I know that 
ddrescue can be used on individual files within a filesystem, but I 
don't know for sure if that's true of dd_rhelp.

Anyway, I should probably mention I've never used any of these on a 
DVD.  I did, however, use it on a failing hard drive and recovered a lot 
of good data (until the hard drive completely failed during the recovery :).


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