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View Full Version : Very Strange Audio Sync Issue


adamschroeder
19th January 2004, 19:35
I know this is a long shot... if anyone has any suggestions we would greatly appreciate it. Right now it seems like we are just grasping at straws.

Here are some ideas we have running around in our head.

1.) the problem has something to do with the deinterlacer or line double on DVD player... or possibly the playback device when dealing with two different types of video.

2.) the white levels on the computer generated graphics are level 255 white, while the white shot on video would be less than this....


Here is the situation:

There is a very strange audio problem with a DVD we created using TMPGencoder and TMPG DVD Author 1.5 on SOME players.

The audio is a PCM stream as mentioned above. We had created a 14 minutes clip that consisted of a spokesperson keyed over computer created graphics and several talking heads shot with a white background (but not keyed). The source was edited on an Avid DS system and exported using Huffy2.2, the audio is synced perfectly on the huffy AVI.

On my Panasonic XP30 DVD player the audio on the talking heads was slightly out of sync, while the audio from the spokes person was fine. The video switches between both types of scenes probably 10 times throughout the video.

On all other DVD players we tested and all software DVD players on the computer the audio is synced perfectly throughout the entire video.

Interestingly, when I disabled the progressive output on my Panasonic it fixed the problem.

Our client has informed us that they are expierencing the same audio syncing problems (with a Pioneer player and Pionneer Plasma screen) although disabling the progressive output on their player did not fix the problem.

We burned a new DVD using the latest versions of the TMPG encoder and DVD author and I encoded the audio to AC3 format.

This seemed to fix the problem on my player, the audio and video played fine throughout the entire video with or without progressive output enabled.

However when we tried to verify that this solved the issue and played the old DVD. The old DVD which yesterday had reliably produced audio syncing problems was suddenly working fine.

Obviously this doesn't make any sense and is probably impossible to troubleshoot but I thought I would give it a shot in case you have ever heard of similar problems or have any suggestions.

We have sent the new DVD along to the client but they are still reporting the same audio problems. The client is at trade show in Orlando so we do not have access to there equipment. And since we can no longer reproduce the error on the Panasonic we are at a loss.

The client is ouputing from the DVD player to the plasma screen using the composite output, and using the DVD player to output stereo audio to a wireless headphone transmitter. If the wireless transmission is a problem then it should be wrong throughout.. not just on certain scenes.

Any thoughts or suggestions would be greatly appreciated!

Thanks for your time,

Adam Schroeder

dvd_master
20th January 2004, 05:30
Wait, so is it that one of the channels is out of synch, but another part of the audio is NOT?

Try this:

You have an AVI that you KNOW is in synch, correct? Open it in VirtualDub, and play (to make sure it is still in Synch). If it is, Save the WAV file (make it the 4800 PCM), and then frameserve the video into Tmpeg and reencode it. You might want to tru deinterlacing the video via the filters in Virtual Dub before frame serving too, BTW. This might be a solution to the prob.

adamschroeder
20th January 2004, 14:48
Thank you for the reply. The problem is not that one channel is out of sync, it is that some scenses are out of sync but only on a few DVD players.

Maybe here is better example:
A = A spokesperson keyed over computer graphics
B = An unaltered interview of someone shot on a white background.
C = General video running footage

If you watch the video it switches between scenes something like this. The DVD is a single Title, Single Chapter.

A B A B C A B A B A C A B

On a few DVD players (one which we can no longer reproduce the error) the B scenes are slightly out of sync. The A scenes are always in sync regardless of the player. The C scenes just use voice overs so we can't tell if it is slightly off or not.

Again, most hardware DVD players and all software DVD players play the entire video in sync throughout all scenes.

The only difference we can see between the A scenes and the B scenes would be the white level and the the interlacing.

I tried another DVD which I deinterlaced with AVISynth and Kernel Deinterlacer 1.33. TMPGenc still saw the video as interlaced but I marked it as progressive. The client says that that disk has the same problem but I have not been able to verify it for myself. Maybe I should try a more tradional deinterlacer in VD like you suggested. The audio is 48Khz... and when I opened the AVI in VD the audio length matches the video lenght.

BTW, I usually frame serve into TMPGenc usering AVISynth (where I will crop, resize, and possibly other filters). Would Virtual Dub be a better option to use?

SomeJoe
20th January 2004, 16:20
Originally posted by adamschroeder
A = A spokesperson keyed over computer graphics
B = An unaltered interview of someone shot on a white background.
C = General video running footage

If you watch the video it switches between scenes something like this. The DVD is a single Title, Single Chapter.

A B A B C A B A B A C A B


What camera was used to film each scene? How was each camera footage captured to the computer?

I'm thinking unlocked audio may be the culprit here.

adamschroeder
20th January 2004, 16:49
The A, and B scense were shot with a BetaCam SP camera. I'm not sure what the general running footage (C scene) was shot on but we received it on a Beta tape.

All camera footage was capture to an Avid DS machine as uncompressed video at a resolution of 720x486. It is a studioZburst capture card.

After editing... the A scenes are almost entirely computer generated graphics (After effects, and Avid DS created) while the B scenes contain straight cuts from the video shoot with just a little color correction.

The entire video when completed was exported uncompressed as a Huffy2.2 AVI. We had to use 2 files to overcome the 4GB limit of Windows NT. We took the two files to a Win2000 machine where I combined them with AVI Synth (which I was also using to crop to 720x480).

I opened the AVS file in TMPGencoder, ran through the DVD wizard (using linear PCM audio). I then took the M2v and wav file into DVD Author 1.5, and created a simple menu with a play button.

After DVD author is finished building the DVD, I used IfoEdit .91 to change the aspect ration from 4:3 to 16:9. I then burned the DVD with the software provided with DVD author. Our burner is a Pioneer DVD-R and RW 106D.

What is unlocked audio? How do you lock it?

I am going to try some other disk media and an older Pioneer burner we have on a Mac to see if that helps any as well.


Thanks for trying to help me us with this!!

SomeJoe
20th January 2004, 20:50
If cameras were Beta SP and capture was all done on Avid with a D1 capture card, I think it's safe to say that unlocked audio is not the problem. :) Unlocked audio is a problem with some low-end consumer equipment ... basically what happens is that the audio sample clock is not locked in-step with the video sample clock, and when the sampled audio and video are separately processed after capturing, they can get out of sync when played back. But I don't think this would apply to you - Beta SP & Avid are professional products.

The only other thing I can think of is possibly an unknown problem with the DVD authoring application you're using or a problem with the audio from the Avid system.

PCM audio for DVD needs to be 48kHz, 16 bit, 2 channel. There are some DVD players that have certain problems with PCM audio, and these problems can be exacerbated if the audio is at a different sample rate or sample size. Check the audio with Sound Forge/CoolEdit/Audition to make sure it fits those requirements.

I think you're on the right track to make the audio AC3 if you have a Dolby-approved and licensed AC3 encoder. Most DVD players are more consistent with playback of AC3 because Dolby maintains tight control of the decoder chips & code.

I would also try a different DVD authoring program. I know of no specific bug which would cause the behavior you describe in TMPegEnc DVD Author, but it's worth it to try a different DVD authoring program just to see.

Finally, there may be some sort of problem with the HuffYUV codec. Perhaps it isn't delivering synced audio on decompression for some reason. If you have the disc space to edit uncompressed D1 on your Avid system, would it be possible to export the project to uncompressed AVI to feed into AVISynth? This could remove another question mark in the chain.

You said you're using DVD Wizard for MPEG-2 compression ... I'm unfamiliar with this application. You may want to try a different MPEG-2 encoder (does the Avid system have one?). Perhaps CCE would be better (CCE Basic is only $58). If that's not an option, you may want to run Bitrate Viewer on the resulting .m2v from DVD Wizard and get a length in frames/SMPTE timecode. Compare this to the length of the pre-compressed AVI file and also compare it to the length of the audio .wav ... make sure everything is consistent.

If all lengths are good at that point, then it has to be something in the DVD authoring/muxing engine.

You can track this problem down ... it's just a matter of getting the right set of tools together so that you can gather data and make meaningful judgements.

adamschroeder
20th January 2004, 21:12
Thanks for the help. I will try some of your suggestions. For clarification I used the wizard within TMPGEnc Plus to create the DVD files (m2v and wav)

If the problem lies in the codecs not delivering synced audio, or something is wrong with the DVD/muxing engine then why does the DVD play back correctly on most machines? And why is the audio syncing only a problem on select scenes?

Do you think the problem could be caused by the change between mostly progressive to fully interlaced video? On my Panasonic XP30 player the problem went away when I disabled the progressive output.

The latest version of TMPegEnc DVD includes a licensed AC3 encoder.

The Avid DS is an older system (version 4.0) so it does not have a lot of digital export options. Do you know of an Mpeg2 encoder that works like a codec (like Huffy, Indeo, ect..)?

Again thanks for the suggestions. I will give them a try.