[mythtv-users] Working with DVD ISO images

[Brian Wood]

On Tuesday 16 December 2008 17:30:23 Alex Butcher wrote:
> On Tue, 16 Dec 2008, kenneth at berrypatch.net wrote:
> > I have somewhat better understanding now, thank you.  Todate all I have
> > ever used is mytharchive.  I just checked my mythweb and don't find
> > anything like mythburn.  Tonight I will do some more research on
> > installing and use of mythburn.
>
> Mythburn is an obsolete pre-cursor to Mytharchive, and as such, it doesn't
> do what you want.
>
> You can either use command-line tools like dd and growisofs to rip and burn
> a DVD (respectively), or, more likely, use something like k3b, which has
> 'Copy DVD' and 'Burn DVD ISO image' options. As you've reported that you've
> used k3b to burn the ISO already, either the ISO is damaged in some way
> (e.g. due to copy protection, or damage to the original disc) or writing
> the data too quickly to the media you're using has resulted in a bad burn.
>
> If the problem you're running into is copy protection, then this is not the
> place to ask for further information.
>
> If the problem you're encountering is a damaged disc, try ripping more
> slowly (if you're using k3b, you'll probably need to add a 'speed=1' or
> whatever parameter to 'readcd' in Settings->Configure K3b->Programs->User
> Paramters), using a different drive, increasing the number of read-retries
> during the ripping phase, using some version of ddrescue to rip, or
> professionally cleaning/polishing the disc.
>
> If the problem is a bad burn, try better media (look to see if your
> writer's manufacturer provides a media compatibility list), look for
> updated writer firmware, or burn more slowly.

It's my understanding (please correct me if I'm wrong) that optical disks 
ALWAYS have errors, and even more errors are generated when the disk is read.

CD and DVD drives have error correction of some kind, and as might be expected 
the quality of that correction varies from drive to drive.

So - just because a disk or an image seems to work OK in one drive, does not 
necessarily mean that the disk is "OK", it simply means that the errors on 
the disk can be coped with by the system (drive, software etc.) being used to 
play it. Change any of these parameters and it might not work.

Different viewers have differing tolerances for problems. I have seen what 
looks to me to be horrendous crap on a DVD playback, while the person sitting 
next to me, looking at the very same screen, claims to see nothing wrong.

So DVDs are not a boolean thing, good or bad, rather they run the range from 
totally unusable under any circumstances to working well on just about any 
setup, and they can be anywhere in between.

So be careful using "it works in my other machine" logic when troubleshooting 
DVD problems.

Higher speeds, on either read or write, can't help but increase errors, I 
would think.

If anyone knows more about this I'd be happy to see this confirmed, or 
refuted.

Alex is correct in referring to copy protection as "damage". Such a system 
intentionally degrades things in some way (remember the laser holes in 
floppies?).

-- 
beww
beww at beww.org