About MPEG-like files timecode

[grendizer]

I have found on the web some articles saying that MPEG-like files (*.mpg, dvd's, vob's, divx encoded videos), do not have a fixed lenght, their lenght fluctuates according to the video player software.

This results in a lot of problem, 2 of the main problems are:
- The video player software does not show the real lenght of the movie.
- It is not possible to synchronize subtitles files with some video files.

So is this true that MPEG-like files do not have a fixed lenght, and how can I solve these 2 problems?

Here are some documents:
- http://groups.google.com/group/comp.compression/browse_thread/thread/b706baabc73727a9/...rnum=10&hl=en# (go to the top of the page)
- http://www.urusoft.net/forum/viewtopic.php?id=148

[Krispy Kritter]

The length doesn't fluctuate. If you record/create a 60 minute mpeg file, it will be 60 minutes. I've seen corrupt/damaged mpg files report different lengths in various players, but the file is still playable and not noticably shorter or longer.

If you are having specific issues with a file(s), you will get better answers/help by asking specific questions.

[manono]

Hi-

I have found on the web some articles saying that MPEG-like files (*.mpg, dvd's, vob's, divx encoded videos), do not have a fixed lenght,

As Krispy Kritter says, of course MPEGs have a definite length. Many, if not most, players will give it wrong, though. One guaranteed way to find the length is to make a D2V project file using DGIndex, make an AviSynth script out of it, and then open the script in VDub(Mod). And there's no problem at all getting the correct length of an AVI (like DivX or XviD). Every player I've seen gives the correct length.

- The video player software does not show the real lenght of the movie.

That's right. But that proves nothing.

- It is not possible to synchronize subtitles files with some video files.

I've read of problems synchronizing subs to MPEG video. I've never had the problem, though, because if my source is an MPEG of some kind, I make an AVI from it and synch off of that. Or extract the audio and synch off of that. They'll be in synch with the MPEG after I get done.

[grendizer]

Well here is a problem I had with VOB files.
I bought Lord of The Ring full edition with 12 DVD's.
The episode 1 of the trilogy has 4 DVD's and 2 of them are making of's and documentaries.
The problem is they don't have subtitle (english is not my mother language so I enjoy watching english spoken movies with english subtitles, so I can understand everything).
I found the subtitles for these documentaries on the web, and I started to work on synchronizing them with the VOB files.
To play the VOB files, I used Media Player Classic.
So I go to the time 10mn 00 seconds and I see a scene, then I go to time 25mn 00s and I see another scene, then I go back to 10mn 00 s, and I see a third, different scene!!
Have you ever found such a problem?

[Midzuki]

It is okay to use MPC to open mpeg files, but if you want
subtitle synchronization, Subtitle Workshop is the appropriate application.

========================================

P.S.: What is the version of MPC that you are using?
If it is one of the most recent, ... je le regrette beaucoup.

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[Nelson37]

First, those are not articles, they represent some user's opinions, one of them yours.

Second, no one except you is saying what you appear to be saying.

The problem the others are talking about is a known one. The variation or problem is not in the MPG file or spec, it is in the particular playback software.

Many softwares, and I can absolutely verify that Subtitle Workshop is one of them, have problems displaying correct time during playback, and most especially if you FF and RW, or "scrub" back and forth.

So I fell back on a software that has always worked, and never, ever failed, to correctly display time values. VDubMod. I used that for display and time checking, and ignored the video display in Subtitle Workshop. This prog does several things well, but IMO cannot be relied upon to get accurate subtitle synchronization.

This after many hours spent adjusting times on a converted file, and failing, then simply playing the file and subtitles with a standard playback software with NO FF OR RW. The file which I had thought somehow completely unstable played with near-perfect synch, as good as it gets for converted Closed Captions.

The problem was Subtitle Workshop. As mentioned in the threads the OP linked to. Many progs have similar issue. Only way to get a valid test is either uninterupted playback start to finish, or use Vdub and a Subtitle viewer seperately and manually check time codes.

[Midzuki]

Many softwares, and I can absolutely verify that Subtitle Workshop is one of them, have problems displaying correct time during playback, and most especially if you FF and RW, or "scrub" back and forth.

That's interesting indeed. At least on my computer,
Subtitle Workshop has always displayed correct time during playback/rewinding/
fast forward; on the other hand, several weeks ago I decided to upgrade my
Media Player Classic and as a consequence I was rewarded with total loss of aud/vid synchronization whenever I wanted to FF or RW the movies. So I gladly returned to the "old", "obsolete" and "outdated" version I had been using until the day before.


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[Nelson37]

This apparently varies by the version of the program. Possibly other factors as well.

I deal almost exclusively with captured files, many with embedded pulldown, and this problem is quite common with many softwares. The problem appears to go away once the final DVD is created. These are rarely played with software, however, and almost never edited again, so the testing on this is somewhat limited.

Reminds me very much of issues I had with SVCD, where the muxing and burn/imaging program had a very large effect on synch with FF and RW.

[grendizer]

Hello all, thanks for discussing this.

From what I understood, to explain this problem, there are 2 theories : 1) The video file is responsible for the problem and 2) The video playing software is responsible for the problem.

I will update my codec FAQ with what I learnt here