Muxman generates a corrupt VOB. What now?

[Asterra]

I'm replacing a DVD's audio with my own. Everything's valid. The bitrate of the ac3 file matches the original.

First thing I tried was muxing the video together with both the original and my new audio. When I started scanning through the result to see how it went, I happened to discover one spot where the video goes corrupt, briefly producing artifact phenomena characteristic to corrupt interframe video. I did not bother to watch the whole movie to find more.

I tried again, this time with just my new audio, but again the corruption was there, in the same place.

It is not there in the original VIDEO_TS. It is not there in my demuxed .M2V. I did remember to load chapters from the Celltimes.txt file, if it matters.

I guess what I need is some sort of alternative to Muxman which will still let me complete the process of replacing the main movie's PGC - something which won't generate an unusable result. Barring that, perhaps someone is familiar with this phenomenon and knows of a fix. It is Muxman demo version 0.16.7.

Thanks.

[usually_quiet]

Test the same files with IFOEdit or DVDAuthorGui.

[manono]

I'd also suggest authoring with IFOEdit and then checking, but I'd expect the same corruption in the same place. How did you demux originally?

[Asterra]

Demuxed with PGCdemux.

Actually I just tried building a disc from scratch in Encore, using the same assets, and I got the same result.

My best guess at this time is that the AC3 file I generated, despite playing without a glitch both alone and muxed, is somehow forcing the video to go corrupt once it is muxed together (regardless of what I use to play it). I used a program called WAV to AC3 Encoder. Originally I had used Adobe Audition (possibly via AC3Filter) but the AC3 file it created had the audio about half a frame out of sync, whereas WAV to AC3 Encoder did not generate this anomaly.

I'll grab IFOEdit (it was the last step anyway) and see how it likes it.

[Asterra]

Gave IFOEdit a shot. Bizarrely, the corruption phenomenon is more pronounced with IFOEdit's mux than with either Encore's or Muxman's. Corruption flashes twice (two consecutive i-frames) and the in-between frames struggle to deal with it.

[manono]

My guess is that the corruption has nothing at all to do with the audio. You can test that theory by using Muxman without audio. My next guess is that there are 2 (or more) VOB IDs, and the corruption occurs where they join. This is just a wild guess, though, because even with 2 VOb IDs I've never seen the corruption of which you speak. Open the PGC again in PGCDemux and tick 'By VOB ID' instead of the default 'By PGC' and if there's more than one VOB ID, check if the changeover is at the same place as the corruption.

Alternatively, you might try opening the VOBs in DGIndex and then File->Save Project and Demux Video. Use the resulting M2V in Muxman.

[Asterra]

"Solved" in a way. It seems that the mpeg2 codec used for playback must have an issue which causes this corruption problem. Playback in Premiere Pro or TotalMedia does not reproduce the corruption.

However - and perhaps I'd better start a new thread about this - I'm having familiar audio sync issues.

I finely crafted the audio portion of my project from within Premiere Pro. When I loaded the unmuxed, original .m2v and .ac3 into Premiere Pro, their timelines did not agree: The ac3 audio was some 9 frames shorter than the video.

This seemed improbable. Nonetheless, I faithfully lined up my new audio so that it was a frame-perfect match for the video.

Now when I play back the muxed result, it starts out fine but by the end of the movie it's noticably out of sync. If I were to guess, it's the same nine frames of temporal inaccuracy.

I am an old hand at Audition and I do know how to fix these things. But it would be nice to know what I can do in the future to prevent this from happening. At a guess, Premiere Pro is lying to me. Obviously the demuxed audio should have matched the demuxed video, and the "discrepancy" is probably some shortcoming of Premiere Pro. Is there a setting I could adjust to force them to match? Shrug.