vob / mp2 problem

[mikewillnot]

If this is a stupid question, please forgive me and just point me to an explanation. At present, after much searching, I can't find it. I have some files (clips), most of which started out as VOB's ripped and split from commercial DVD's. Purpose: editing in ULEAD Video Studio, eventual goal DVD. At some point, I ran IFOedit on the files to create IFO's for test burns. I probably shouldn't have done that, as it changed the original files. I then changed the extension to .mp2, for editing in ULEAD-VS. Now, the files behave oddly in editing. In ULEAD-VS, there is no audio. If I play the .mp2's in any PC player, no audio. If I change the extension to .vob, and play the file directly with PowerDVD or WinDVD, presto: normal audio. .mpg, no audio. Could someone pleeeeeze explain to me what's going on here, or steer me to some info or a guide that explains? I'm betting there's a simple fix, but I could be wrong. THANKYOUTHANKYOUTHANKYOU.

[fccHandler]

Most likely the audio is AC3, which is something specific to the DVD format. AC3 and DTS audio is stored in a private stream in the VOB. Normal MPEG decoders (like Ligos, which Ulead uses) don't see the audio because it's not an MPEG audio stream. Only programs that understand the DVD format will know how to find the audio.

[mikewillnot]

Ahhhh.
Is there some way to look at the files and verify this, I wonder?
[UPDATE: Cancel this question. I checked the files out with VOBedit, and indeed, they're AC-3 audio.]

And, if I do my editing on the "audioless" mp2's, and then export, the audio may come along just fine. ULEAD has several export methods, one of which builds VOB's and IFO's. Or will it drop out somehow?

Seems curious that with a single file, with an .mp2 extension PowerDVD won't see the audio, but sees it when the extension is .vob.

[fccHandler]

Originally posted by mikewillnot
Or will it drop out somehow?
I don't know. You'll have to try it and see.

Seems curious that with a single file, with an .mp2 extension PowerDVD won't see the audio, but sees it when the extension is .vob.
Just guessing, but it sounds like if you give the file an .mp2 or .mpg extension it treats it as a normal MPEG, but with the .vob extension it sees it as a DVD object file. My ATI MMC behaves in a similar manner.

[jggimi]

Moved to the Audio forum, as this has nothing to do with capture.