[MPlayer-users] Rescuing a scratched DVD

[Corey Hickey]

Magnus Damm wrote:
> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> I think this is related:
> 
> I usually rent DVD:s and use mplayer to watch them on my media box.
> This is a ok solution as long as the DVD is without scratches/finger-
> prints. Sometimes (1 out of 10 maybe) the DVD is scratchy/dirty and
> my DVD drive together with Linux and mplayer will totally slow down,
> I guess trying to read the problematic area of the disc. 

Yeah, I've seen that too with rented/borrowed discs. I try to keep
peanut butter away from my optical media, but I guess that doesn't apply
to everybody.

> 
> I have found out that my Linux kernel likes to disable DMA when a
> read error occurs and I have to manually use hdparm to re-enable 
> it again. And this can only be done after all IO has completed,
> I usually have to wait a while an look at the logs that tells me
> that a certain sector/whatever of the disc was problematic. And
> this takes a lot of time and is generally a PITA.
> 
> So how to people solve this? Rent VHS instead? =)
> Buy a regular DVD player for 100 EUR? =)
> Can I tell the kernel to keep DMA on even if errors occur while 
> reading the DVD? Is there any way to stop the kernel from reading 
> sector by sector very slow from the DVD?

Get a small flashlight, a bit of water, and a rag (or spit and your
shirt, if you don't want to get up). By holding the flashlight at an
angle right next to the disc, you can see smudges and stuff really well
without blinding yourself. Try to scrub off anything you see that might
be distorting/obstructing the laser beam (don't use anything abrasive,
of course). Then, re-enable DMA and try reading the disk again. It'll
probably work fine, unless the disk is actually damaged rather than just
dirty.

-Corey