Subs out of sync when remuxing a cut DVD

[PiPi FiLiPi]

Hey,

I'm currently trying to backup my Band Of Brothers DVDs and ran into some problems...

Each DVD contains 2 episodes and each of those episodes has like a 2,5min long intro, which I want to cut out to gain more space. That, I have successfully done using VobBlanker and when I play the cut DVD, everything is in sync and just perfect.

But my problem arises elsewhere...

Later on in the process, I need to demux each PGC (3 PGCs - 2 episodes and 1 WB logo) using PGCDemux and then remux them individually with MuxMan.
When I try to play these newly muxed "DVDs", the subs are out of sync (they are late) as if the intro was still there. The audio, though, is fine. (if anyone is wondering why I need to demux / remux, it's because somehow during the cutting, the AC3 files got damaged and the DI4U reports an error when processing them).

So, if anyone has any idea as to what the problem could be and/or possible solutions, I sure would be grateful.

[r0lZ]

Hi, and welcome to the forum.

When cutting the beginning of a VOB, you have probably lost the original synchro.

You could try to demux the whole PGC, with the intro, and add a chapter point right after the intro. Remux all, and cut the logo in your final DVD.

Also, if that can help, the PSL plugin for PgcEdit has a function to display the original play time of any title. It should normally be around 0, but since you have removed the intro, it is probably equal to the length of the logo. It's probably the exact timing you have to substract to the subpics when you remux. However, I don't think you will be able to use such a long negative delay when remuxing.

Another method is to recreate completely the subpics with SubRip and Subtitle Creator, but it's tedious to do!

[PiPi FiLiPi]

Thanks for the quick reply...

The thing is, I don't really remove it from the very beginning... first, there's a minute and a half I want to keep, then there are 2,5min which I delete, and then, there's the movie.

But will try adding the chapter points.

Just me being curious... why does the DVD work normally before I remux it? :confused:

[jsoto]

Trying to guess...

VobBlanker does not modify the PTSs at all (like dvdshrink), so the relative timings between the streams are still OK. That means, the cut title w/o demux will play fine

PgcDemux extracts the subs with its PTSs (which are NOT modified) , but the video PTS is lost in the m2v file.

So, Muxman applies 0 msec of delay to audio/video but it still applies the PTS stored in the sup file (which is the original one), resulting in a sub delayed versus the video.

I think there are tools to modify the delay in the sup file...

Anyway, I'll keep it in mind for new releases of pgcDemux.

jsoto

[jsoto]

No, I'm wrong....

After reviewing pgcDemux code, it is already substracting the PTS of the first Nav pack in the sup file....., so, I have to investigate more deeply what is happenig.

jsoto

[PiPi FiLiPi]

Could it be something to do with open GOPs in the video that I cut?

[jsoto]

No. Open Gops (VB change them to broken GOPs) could affect to the correct decoding of the first frames, but not to the delay

I think the problem is related with the PTSs...

I'll do some tests tomorrow, I'm currently a little busy

jsoto

[PiPi FiLiPi]

Yeah, I thought so about the GOPs.

Let me know if you come up with something, will do a couple more tests myself.

UPDATE:
Tried demuxing the DVD using VobEdit. It produced the same files as PGCDemux.

[jsoto]

first, there's a minute and a half I want to keep, then there are 2,5min which I delete, and then, there's the movie.
Sorry, I didn't see you are taking away a part of the movie in the middle...and this is the problem.

So:
Cut the first part (1 min),. demux it and remux (clip A)

Cut the second part (from 3,5 min until the end) demux and remux (clip B).

Join the two parts... may be you can use VobEdit to join them,and after use IfoEdit to create IFOs.

jsoto