Dr Who. who insisted on going down to the city and in peril from the daleks, but not responsible for problems on my Media Center 

The Dead Planet

Travelling to a desolate and seemingly dead planet, the Doctor and his companions find a city which seems virtually untouched.  The Doctor tricks his companions into an expedition down to the city in order to take a closer look at it.  He does this by convincing them that the TARDIS requires some mercury for a part called a"fluid link" to repair it.

The planet is Skaro and the inhabitants turn out to be the race that are to become his greatest adversaries…..

As it turns out, my latest Media Center (MCE 2005) journey had a few parallels with the plot of the DVD which started the problem in the first place….

My kids are going through a bit of a Doctor Who phase at the moment, and as a result we borrowed four DVDs from the council library.  The first 3 were remastered versions of the original first 3 episodes.

As it turns out, library DVDs tend to get very scratched.  In this case we had all sorts of trouble playing the second DVD.    We had to give up on this one, just as Susan had the frightening encounter with the Thal in the radioactive forest….

The Survivors

The third and subsequent DVDs played then started exhibiting a very strange problem.  The DVD sound was distorted and the playback was jerky.  More investigation revealed that audio CDs also "crackled".

I finally isolated the problem to the DVD player itself.  I cleaned it using a CD cleaning kit. (About 8 times) I then proceeded to clean it with a cotton bud.  Neither of these actions produced any result.

The Escape

Was the problem software?  Much googling revealed the problem.  Apparently an IDE DVD player on a computer has two modes of operation, DMA mode (Direct Memory Access) and PIO Mode (Parallel IO?).

The Ambush

DMA mode allows data to be transferred directly from the DVD to memory, which makes it very fast and efficient.  PIO mode requires the interaction of the processor, which isn’t so fast (especially with Media Center trying to render video etc at the same time).

The Expedition

Apparently Windows XP has a feature that switches automatically from DMA to PIO when trying to read a scratched disk, as PIO mode is more tolerant of problems.

The Ordeal

The bad news is that it stays in this mode, resulting in stuttering DVD playback and crackling CD audio.  This change is permanent (it survives reboots).

The Rescue

Fortunately, just like the 1963 footage of the early episodes of Dr Who were remastered back to their original condition, it’s possible to switch Windows XP back to using DMA.

The following excellent article provides a vb script (that worked for me) that does this:

DMA reverts to PIO

My wife is returning from a trip away tomorrow and doesn’t like me "playing around" with "her" media center.  This information has saved me and hopefully (via Google) this information may save some of you also.


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