unusual a/v sync problem

[djloewen]

I'm not sure where to post this, since I'm not sure where the problem lies :).

I've encoded a number of movies with no sync issues, and I'm familiar with most of the common causes of such issues. This one has me stumped. I'm trying to encode a porn (which I have heard is notoriously problematic), and I find that the audio gradually goes out of sync with the video (by the end, the audio is maybe a quarter of a second ahead of the video). The movie begins perfectly in sync.

It is a multi-angle stream, and I have tried stripping the angles in various ways (such as DVD Decrypter in IFO mode, or a rip in FILE mode + PGCedit + VOBblanker). I have successfully encoded other movies with angles, and I'm quite sure that this isn't the problem. I have also carefully stepped over the points where the angles begin/end, and I see and hear no abnormalities at these points.

What I did notice is that if I rip it in IFO mode and have it split the files into 1GB chunks (it's 2.6GB total), and then load the chunks SEPARATELY into DGindex, the first has an audio delay of 0ms, but the next two are marked as having a delay. If I watch one of these in VirtualDub, the sync problem will be there.

If, on the other hand, I rip it in IFO mode and have it split the files by cell, it seems that each file is nicely in sync. Running them through DGindex shows a delay time of 0ms. This leads me to believe that at some of the cell/chapter points the audio duration is not as long as the video, and so when it "glues" the audio from the next cell to the end of the previous one it will end up starting a bit early. I could be way off here, btw :). In case it helps, when I load the angle-stripped movie into PGCedit the cell flags are all at "10".

So if this is the case, I need to know how to get it to "reset" the audio stream at each of these points. The only solution I've thought of so far is to encode each cell separately, then use VirtualDub to glue them together. This is obviously not the elegant solution that I'm hoping for.

HELP!!!

[setarip_old]

Hi!

Have you tried setting DVD Decrypter to rip the movie as ONE .VOB?

[djloewen]

So I've just tried that, and... well the plot thickens. I encoded it in Gordian Knot the usual way (DGindex, AVIsynth, DivX codec...) and I've got the same problematic output file as always.

BUT if I take the 2.6GB .vob, rename it as a .avi and play it in Windows Media Player, it plays perfectly. Might this mean that DGindex is doing something wrong when it strips the audio stream?

[setarip_old]

As an experiment, try using MPEG Mediator or VirtualDubMOD (instead of GK) to convert the 2.6Gb .VOB to .AVI...

[djloewen]

I dropped the .vob into VirtualDubMod, and when it was finished parsing it had the sync problem.

As a (probably irrelevant) point of interest, when I play it in WMP the sync problem isn't there, but it shows the file length as being 4:35. The movie will play past that point, but it stops counting at 4:35. I don't see any chapters with a duration of 4:35, and at 4:35 in the movie you're halfway through the third cell. The point is, I have no idea where WMP gets that number from.

[setarip_old]

when I play it in WMP the sync problem isn't there, but it shows the file length as being 4:35.Sounds like you're 90% of the way home ;>}

Load the .AVI into VirtualDubMOD and (from the "Video" dropdown menu) scan for errors - and then mask them and save with a new name...

[djloewen]

No luck there. The scan turned up 0 bad frames.

[setarip_old]

I have no additional suggestions.

However, I would once again suggest that you try using MPEG mediator to convert the 2.6Gb .VOB to .AVI - and see if it yields acceptable results (You probably DO want to make sure that the .VOB you create contains only ONE angle)...

[djloewen]

Well thanks for trying :). I downloaded MPEG mediator, as well as the 7-Zip decompressor, which tells me that the .7z file is "broken". I'm not very hopeful that that would work anyway.

I am positive that there is only one angle left in the .vob.

Anyone else have any ideas?

[setarip_old]

Try downloading MPEG mediator from here:

http://seemoredigital.net/05_How_to..._Files/MPEG_Mediator_1.5.html

[dwm4444]

I've had similar problems a couple of times before, converting early porn DVDs that were made from movies that were produced before DVD existed. A big marketing gimmick at the time was all the angles from which the action could be observed. Basically they would take a 10-minute action scene and chop it up into a 6-minute scene with 4 minutes of leftovers from which to make switchable "angle" views.

I remember one such was the classic "Bad Wives" (the 1997 version, not the newer one). They took a perfectly good movie that was originally almost 2 and a half hours long in the VHS version and cut it all to hell, shortening it by like 20 to 30 minutes and using the scraps to make angles from. But, hey, it's got 4 angles! When I tried converting my DVD to an avi, I ran into bad sync problems, even though I did a Decrypter ifo rip of the main angle and fed that to AutoGK. The audio started out OK but started drifting rapidly; it was considerably longer than the video, as if some of the audio from the other angles remained. I attributed it to sloppy authoring, this being the pioneer days of porn DVD. I've never seen this problem with "mainstream" commercial DVDs. I've used AutoGK almost since it came out so I know how to isolate an angle with a Decrypter ifo rip, as do you, but it didn't work in this rare case.

But I found a way to fix it in an old guide from Digital Digest (since taken down). It's reproduced here:
http://forum.videohelp.com/topic331147.html#1714317

It sounds like you may have already tried a variation of this method, since you say you've used "FILE mode + PGCedit + VOBblanker" and that's what this method uses (except for VOBblanker). But I thought you could look it over and see if it differs from what you've already done.

This did the trick for me. Hope it helps you. Holler back and let me know if it worked, in case others have a similar problem and come across this post.

Best regards

[djloewen]

setarip: That is where I downloaded it from. Maybe 7-zip doesn't like Vista?

dwm4444: thanks for the tip. Your problem does sound very similar to mine, but having followed those instructions to the letter, I am left with the same screwed-up output file. FYI the movie is "Chasey Loves Rocco", from 1998.

The impression that I have is that the video is seamless, but the audio track has "blank spaces" in it where there is simply no interleaved audio at all:

Chapters: 1 2 3 4 5 6 etc
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
aaaaaaaa aaaa aaaaaaaaa aaaaaaa


So, if I'm watching the stream directly like in Windows Media Player, it just plays those parts without the sound, and starts the sound up again when it comes to the next section. But when I load it into something that parses the audio stream (like DGindex or VirtualDubMod), it glues all of the audio sections back-to-back, effectively "deleting" the blank spaces needed to keep things in sync.

If this is the case, I need a way for the audio to be parsed in such a way that it recognizes these spaces and adds appropriate blank chunks to the output audio files, or maybe not be parsed at all but read directly from the .vob, in such a way that it reads and keeps the blank spaces.

Thoughts?

[djloewen]

It seems that this forum converts multiple spaces into a single space. So that "diagram" in my last post is not how I intended it. If it makes no sense, go ahead and ignore it :)

[dwm4444]

It's not an elegant solution, but you could try changing the audio length. In Goldwave, for example, after demuxing the audio, select all of it and click Effect->Time Warp. Or you could change the video length to match the audio: http://www.doom9.org/index.html?/virtualdub_procedures.htm , the "Manual Synching" section. One of these methods might give satisfactory results if your bad frames are not too bunched up. I read somewhere that the average person doesn't notice a/v sync until it reaches the range of about 75 to 125 ms, so you'd have a few frames leeway plus or minus before anybody'd notice.

Also, you might try running your big 2.6GB vob through Avidemux. No DGindex or Vdubmod involved. There's a pretty good comparison of Avidemux vs. Virtualdub here: http://www.excelcia.org/modules.php?name=News&file=article&sid=57

If none of this works, you might find good advice by focusing your question more toward the audio aspect and starting a thread in the audio forum where it might attract the attention of a guru. I don't think that would count as cross-posting.

Good luck. Let us know how it goes. It's probably just a matter of time until I hit a similar problem.