VOB Files Change Durations!?

[ronsweet2]

Hello:

I need to edit large (as big as .99 GB) VOB files by chopping them up into smaller pieces (based on the duration of the clips within it). I downloaded and installed a freeware VOB editor called Chopper XP a few days ago. To view the VOBs, I am using Cyberlink's PowerDVD XP, which came bundled with my DVD drive (FYI, I have a dinosaur c. 10 year old computer, using Windows 2000). Using Chopper XP, I use the "manual extraction" method, where Chopper asks you for three things: the total duration of the VOB, the start marker, and the stop marker.

HOWEVER, when I use a media player (such as PowerDVD XP) to view the VOBs, the durations (length) of the VOB file seems to vary each time!! One time I do it, it is 25:05 (for example), the next time I do it is 28:00, and so on. It does the same thing for the individual videos (clips) within the VOB (i.e.: one time the first clip is 13:05 and then it's only 11:13!) I don't understand why it seems to do this all the time. Obviously, if the total duration of the file varies each time, the markers are incorrect, so it becomes impossible for me to cut and save the individual VOB clips that I want!!

I know that PowerDVD XP is either part or all of the problem, but it is hard to diagnose if Chopper XP is part of it since it can only cut the file accurately if you give it the correct parameters. I have tried several different freeware media players, and have still not been able to find a way around this. Generally speaking, the freeware media players can not even show you the entire VOB file, and therefore the total durations are never accurate. I also have and use the VLC media player, but it does not show you the video, you can only hear the audio (this probably has to do with the codecs, but I don't understand how to fix it).

Using Windows 2000, my options are very limited, especially considering I have to use only freeware.
I believe what I need is one of the following:
a) a way to "fix" PowerDVD XP so that it accurately tells me the durations (I cannot upgrade it because no other available version will work with Windows 2000)
b) a freeware VOB player that will accurately display durations for VOB files (so that I can “chop” them with Chopper XP)
c) another freeware program (or 30 day trial without watermarks) that will display and chop VOB files
d) some other solution I have not yet thought of!

Has anyone else ever experienced this problem at all, and if so, how were you able to solve it??

Ron

[Baldrick]

I would try editing with something else like mpg2cut2 or avidemux.

[G)-(OST]

Hi

One of the best is VideoRedo IMO, but you have to pay for it, however, there is a trial, not sure if it leaves any water marks though, but what Baldrick recomended, mpg2cut2 will do a good job to

Denis

[guns1inger]

I get the feeling you know very little about the authoring process and VOB files. VOBs are (generally) created by the DVD authoring process. A collection of similarly named VOBs constitutes a titleset. A titleset may contain one or more titles sharing similar attributes (aspect ratio, audio etc). A titleset may be made up of up to 9 VOB files, each up to 1000MB in size.

You may well find that the clips you are after are all separate titles, and you don't need to do any editing at all. I would start with VOB2MPG and see if you can simply extract the titles individually, without the need for editing.

[gll99]

I haven't used Chopper XP in a while but I just retried it and cut a couple of parts from a vob. I just used the time line view in the opening panel. I had to play it first or the slider wouldn't move. If you don't select "Display Realtime output", it plays at faster than normal speed which is good and after a while I stopped it and could easily move the slider backwards or forwards and fine tune the cut start point or end point with the << or >> buttons. After marking the in - out section I wanted I just saved it to disk and selected another part and did the same. the lengths look good to me and the start and end points are accurate. Maybe the problem is with the manual extract mode. Maybe I was lucky and twice hit a chapter point but that would be a darn lucky coincidence. They also play fine in KMPlayer.

[gll99]

Apparently I did get lucky because I selected in and out on a scene change and probably hit the right spot. I tried it again and was off by as much as 2 seconds on short clips.

Here's what I found on Doom9 back in 2004:
http://forum.doom9.org/archive/index.php/t-79959.html

Partial thread quote:

In MPEG2 encoding, a GOP is a 'Group of pictures'. Normally a GOP is composed of 12 or 15 frames.
For in-cuts, a GOP can't be split! That's why there's no software that makes frame-accurate cutting! frame-accurate cutting is only possible by reencoding the corresponding GOP!

and look at the section that starts

After a bit more search I found out that Womble Mpeg Wideo Wizard 2003 does frame-accurate VOB cutting editing, but exported file is saved as mpeg rather than VOB. I tried it and it works flawlessly. In Export preferences, there is an option for 'GOP size compliance for DVD recording' and also a toll called 'Mpeg GOP fixer' which - I assume - corrects GOP splits you have mentioned. The software is extremely fast with the added bonus of being able to make several cuts on the file and get rid of all unwanted segments in one step. And the new exported mpeg file is generated without any reencoding so the original audio/video quality is fully preserved..............
edited for size
...............Is it because of all GOP issues you mentioned that MPEG2cut edits VOB with 15-frames accuracy only?
Short answer: Yes!
Long answer (but still VERY simplified): There are 3 types of encoded pictures/frames in MPEG videos:
I-frames, P-frames and B-frames.
If you have a GOP, it typically contains this sequence of frames: IBBPBBPBBPBBPBB
only the I-frame can be decoded without the other frames. all other frames can only be decoded if you also have the I-frame available!!! This is so because P-frames only contains the DIFFERENCE between the previous (I-) frame and the current video picture! B-frames only contains the diference between the previous + the next and the current video picture! If you cut a GOP and loose the I-frame, then you're not able to decode the remaining P- and B-frames!!!

Seems to explain it all.