Is wrong field order causing this audio sync problem?

[dlflannery]

I take the same mpeg input file and author it to DVD via two different processes. One ISO/DVD has a sync problem (whether played on software player or standalone player). When I examine the authored .vob files with gspot I see one obvious difference:
In the "good" file, the TFF interlace field order has been maintained.
In the "bad" file, the field order is switched to BFF.

Can this explain, or at least be related to, the audio sync problem?

Details are as follows:

I create D1 NTSC DVD's (720x480, 4000 kbps bitrate, AC3 audio) starting with "medium" TiVo files (352x480 MPEG2, 2700 kbps, mp2 audio) I have two process paths to do this:

MyDVD path:
1. Edit TiVo with VideoReDo save as .mpg or .tivo, sometimes also do a "Quick Stream Fix".
2. Input edited .mpg or .tivo to MyDVD
3. Set project settings to 720x480, 4 Mbps, Interlaced, AC3 audio 448 kbps.
4. Burn to ISO (then burn to DVD and/or view in PowerDVD).

DVDStyler path:
1. Edit TiVo with VideoReDo and output as .vob or .mpg, sometimes QSF.
2. Input file to gui4ffmpeg (free encoding software from VideoHelp.com). Settings are the same
as step 3 in MyDVD path.
3. Input output .mpg to DVDStyler and author to ISO.

I have one test clip for which the MyDVD version video lags audio by about 200 msec, i.e., just noticeable. The problem does not exist on the DVDStyler version.

Other facts:
1. The sync problem does not exist in the source files.
2. The sync problem does appear in either PowerDVD playback of the ISO or on actual standalone DVD playback.
3. If I rip the .vob files for the clip from the two .iso files, the sync problem does appear when the MyDVD version is played in a software player.
4. Using gspot, the source files are interlaced, TFF (top-field first).
5. The .mpg out of gui4ffmpeg is interlaced, TFF.
6. The .vob ripped from the DVDStyler ISO is interlaced, TFF.
7. The .vob ripped from the MyDVD ISO is interlaced but is BFF (bottom field first).

I have to conclude from this that MyDVD is the cause of the audio sync problem.

I have to wonder whether the reversal of interlaced field order by MyDVD might not be the source of the problem, and I wonder why it does this?

BTW, I was able to correct the sync in the MyDVD ISO by introducing a compensating shift in the input file using VideoReDo.

[machf]

Incorrect field order shouldn't cause audio problems, it would cause video problems, rather...

Why are you encoding to D1 resolution? Half-D1 (352x480) is a valid DVD resolution, and you don't gain anything trying to force a higher-resolution encode from a lower-resolution source...

Finally, have you checked the original file to see if it had an offset for the audio?

[dlflannery]

Why are you encoding to D1 resolution? Half-D1 (352x480) is a valid DVD resolution, and you don't gain anything trying to force a higher-resolution encode from a lower-resolution source...

I make DVD's for several friends and some of their players will not handle anything except strictly DVD compliant D1 with AC3 audio.

Finally, have you checked the original file to see if it had an offset for the audio?

As already mentioned in my first post:
"1. The sync problem does not exist in the source files. "
I can play it in any software player (e.g., WMP, PowerDVD or VideoReDo) without the sync problem.

[machf]

No, you didn't understand my question... I meant if the file has an offset value for the audio as part of it. IIRC, multiplexed MPEG-2 files don't require the audio and video to have exactly matching lenghts, they can indicate an offset between audio and video to compensate any differences and get them properly in sync. If that's the case with your original file, then one of the programs you're using could be reading that offset info and re-applying it to the output it generates, while the other doesn't and instead assigns an offset of 0 (which it shouldn't). All this is just a guess, of course, but I can't think of anything else to explain the problem at the moment.

[dlflannery]

No, you didn't understand my question... I meant if the file has an offset value for the audio as part of it. IIRC, multiplexed MPEG-2 files don't require the audio and video to have exactly matching lenghts, they can indicate an offset between audio and video to compensate any differences and get them properly in sync. If that's the case with your original file, then one of the programs you're using could be reading that offset info and re-applying it to the output it generates, while the other doesn't and instead assigns an offset of 0 (which it shouldn't). All this is just a guess, of course, but I can't think of anything else to explain the problem at the moment.

Ahhh.... So now maybe I can learn something! How can I examine the offsets in the MPEG2 file? I have started using some tools such as gspot and dgIndex.

It seems strange that the Sonic/Roxio product would fail to honor the offsets -- they are not exactly new to the video scene.

Just to make things more complicated, today I used the Roxio software (Easy Media Creator 9) to "import" (i.e. rip) the mpeg back out of the ISO produced by MyDVD9 (I had used DVDDecrypter before) and that mpeg plays with good audio sync in all the software players!

Thanks

[manono]

Hi-

How can I examine the offsets in the MPEG2 file? I have started using some tools such as gspot and dgIndex.

You can open the MPEG in DGIndex and then File->Save Project. It'll give you the audio by default, with any delay written into the name.

If the delay is "0", but the audio is still out of synch, you can fix it yourself fairly easily, if the delay is constant (off by the same amount throughout).

[Scorpion King]

WMP will lie to you. PowerDVD will sometimes lie to you. I haven't tried videoredo.

VirtualDubMPEG2, VirtualDubMod, or Media Player Classic will not lie about the sync.

If the 'original files' will play in sync in these programs then I would suspect your encoding and/or authoring applications.

Like stated above, 352x480 is dvd compliant.

Good luck.

[dlflannery]

Hi-

How can I examine the offsets in the MPEG2 file? I have started using some tools such as gspot and dgIndex.

You can open the MPEG in DGIndex and then File->Save Project. It'll give you the audio by default, with any delay written into the name.

If the delay is "0", but the audio is still out of synch, you can fix it yourself fairly easily, if the delay is constant (off by the same amount throughout).

Thanks manono. I see both .ac3 and .mpa files -- I'm sure they are what you are talking about. They all say DELAY is 0 ms.

Whatever the problem is, one of my authoring processes gets it right and the other doesn't (at least for one test clip). I use VideoReDo to edit prior to authoring and it will take care of constant offsets, but only after I author to find out what offset is needed -- not too convenient!

[manono]

Hi-

but only after I author to find out what offset is needed -- not too convenient!

Nope, not if you don't know before authoring that you need to set a delay. So, when playing both the DVD (like with PowerDVD or WinDVD), or just playing the vobs, like by double-clicking on a vob, to be played in whatever player by default plays your vobs, it's out of synch?

If so, and if the amount it's off is constant, you can reauthor after finding out the amount of the delay. Open a Vob in Media Player Classic. Right-click the screen and go Options->Filter->Audio Switcher->check the "audio time shift" box, and fill in an estimate of the amount of asynch. Hit "Apply" and test it out. Negative values are to make the audio play earlier. 1000 ms= 1 second. Resume playback. Adjust until you get it right. At that point you'll know how much the audio is out of synch and how much to set the delay in your authoring program. If your authoring program doesn't allow for delays, then get rid of the delay using Delay Cut.

When all done, either uncheck the box or set the audio time shift back to 0 in MPC.

Or, if it's only one authoring program that creates out of synch audio, and it doesn't happen when you use other authoring programs, don't use that funky authoring app any more.

[dlflannery]

Thanks for taking the time to help me learn some things, Manomo, including two tools I haven't used yet!

The source videos play in sync in any software player, so I can't know the amount of sync correction needed until I generate a .vob set by authoring.

And yes, if one authoring program works, use that one. I have this feeling that it isn't going to be that simple, i.e., it may not turn out that the one program is always the best one. I also find it hard to imagine that the Sonic/Roxio MyDVD will always be the "bad" program.

Thanks, again

[machf]

So, it wasn't an offset in the original file, then... let me see. Is the audio playing too early?
Ah! You said "video lags audio by about 200 msec". So what might be happening then is that for some reason the encoder is placing extra frames at the start. That would be about 6 frames for a framerate of 29.97fps...

[dlflannery]

So, it wasn't an offset in the original file, then... let me see. Is the audio playing too early?
Ah! You said "video lags audio by about 200 msec". So what might be happening then is that for some reason the encoder is placing extra frames at the start. That would be about 6 frames for a framerate of 29.97fps...

Yes.... When I used VideoReDo to pre-compensate by 200 ms it stated it had removed 6 video frames.

Apparently, for this one particular file at least, the free authoring process (gui4ffmpeg + DVDStyler/DVDAuthor) performs correctly while the commercial one (MyDVD) doesn't!

Gui4ffmpeg (i.e. ffmpeg) uses its own codecs while I believe MyDVD uses DirectShow Codecs, probably the ones that are installed when it is installed.

I guess if the worst problem I have making a DVD is having to precompensate for a small audio sync problem, I will be doing OK!