Re-encoding DVD cleans up the picture 'pulsing' - explain?

[KillingTime]

Hi,

I've been backing up my movie collection for some time now (12 months). I started with DVD Shrink, then moved onto DVDDecryter, then DVDRebuilder, and now RipIt4Me & FixVTS because of the latest efforts to prevent backup etc..

On quite a few of the titles I've backed up (no extra compression, just the raw movie) (TomDickHarrySuperman1, JackJill2001/2010 ...to name a few) I've noticed that especially during dark scenes, the picture seems to pulse once a second (approx). When I say pulse, it looks as though the picture starts off OK and over the second or so, starts to pixilate. This only happens during dark sequences.

If I run the movie through DVDRebuilder (HCEncoder 0.18) the problem is removed.

Can this be right? BETTER quality after running it through an encoder???

I'm playing the movie back via PowerDVD 5.0. I should laso add that using DVDShrink does not remove the problem. Only HCencoder does the trick.

I've searched the forum for discussions about the 'pulsing' but have found nothing.

I'm just curious. What is this phenomenon?

Thanks.

[Mug Funky]

if you re-encode with a different GOP structure then texture will be removed from different frames. so what you're getting is just texture being removed from i-frames (and the frames just after) and making them look more like the later frames from the original GOPs.

also, rebuilder probably has better default encoding settings than what were used in the "pulsy" original.