VobSub and synchronization problem

[eddiani]

Hi, sorry for my bad english.
I recently discovered Gordian Knot, but when I rip NTSC movies (following the guides step by step) the subtitles are slightly lower than the movie, making them practically unuseful.
My first test was with Mononoke Hime, I prefer to have permanent ones so I used vobsub to rip them (in IDX/SUB format) and the plugin to put them on the avs to give to VirtualDub. At the beginning of the movie everything is ok, but close to the end (I checked at frame 185427) they are 28 frames later than the position thy are in the dvd, that's only o,o15%, but on a 2+ hours movie it means more than a second!
So I tried with Fight Club, and the result was the same. I thought it could have been due to ivtc, so i retried with Mononoke left at 29,97, but nothing changed.
With PAL disks, instead, they are always perfectly on synch.
I tryed to think about every possible reason (like an error between 23,976 and 24 FPS...), but the error is too small to be that, and now I have no more ideas. I also looked on the synching guide, but it says nothing about about this problem and I'd like to keep them in .sub format.
Has anybody else experienced such a problem? how could I solve it? is there a way to discover it in advance, without wasting the 5/6 hours of a 2-pass rip to find it out?

Thanks in advance.

p.s. I use VobSub 2.11 (but I had the same problem with 2.09), GKnot 0.23, 1.4.9 and DivX5Pro ads supported.

[sAXIn]

I never ripped a NTSC title with his subtitles but I think the IVTC makes you trouble first of all check the exact movie leight before and after IVTC.
so i retried with Mononoke left at 29,97, but nothing changed.
The DVD player makes kinda IVTC when played so leaving the movie at 29.97 FPS won't give you much.

What is your's IVTC method?
So... the leight shoudn't change but if it changed the desync. will be liner I mean only grow at a given rate as you play back the movie
You can edit the IDX file VobSub gave you and insert delay into it
Like doing with AC3 stream before multiplexing with video.

I strongly recomend doing IVTC by Decomb, Doom9 have a great guide just now out: http://www.doom9.org/decomb.htm
check this out

[eddiani]

The "true length" is another problem I had. SmartRipper says it's 2:13:30, i've watched the IFO quth IFOEdit and it says 2:13:30@30fps, but every rip I tried, video and audio all the same, with GKnot or XMpeg came out 2:13:37, so I suppose that's the real one (and in facts 2:13:30*(30/29.97)=2:13:38, with a reasonable error).
But that's too much, my error is a little more than a second.

As for IVTC, when I wrote the message I had tried just dvd2avi's Force Film, now I tried Force Film, Decomb, GreedyHMA, InverseTelecine and no IVTC at all, and the results are always the same, so I suppose the problem must be in the subs ripping, but I don't understand how it could be, especially since no one else reported anything like that.

Also, the delay's grouth is linear (nothing at the beginning, and it grows with time), so I can't adjust it by simply setting a constant delay :(

[sAXIn]

Try another thing rip subtitles with SubRip and convert frame rate to
23.976 FPS and try , Subtitles ripped by OCR are easy to change and confugure