Lack of Audio Sync on MPEG-1 driving me nuts!

ibliss wrote on 12/5/2002, 10:35 PM
I have an MPEG-1 video file of about 35 mins in length. I am trying to render a 20 minute section into MPEG-1. The audio of the render goes out of sync with the picture. To start with it is okay, but it gets worse over time.

Rendering a WAV file of the audio, and then importing the WAV back onto the timeline it matches in length, but zooming in reveals that the rendered WAV does not visibly line up with the MPEG-1 audio. This becomes apparent at about x7 zoom on timeline.

Here is a link to a screen capture vid which shows what I mean (~90k, .wmv)

Audio Error Example vid

On playback you can hear the echo of the two tracks playing out of sync.

I have searched this and other forums without finding a cure for this. It's not Vegas specific...using XP's wonderful (sic) Movie Maker to render the video produces the same audio error; same result with STOIK video convertor.

Can anyone tell what is happening, and how to solve the problem (preferably within Vegas).

Many thanks,
Mike K

ps: the project setting match those of the source file (ie size, frame rate, pixel ratio)

Comments

SonyEPM wrote on 12/6/2002, 8:33 AM
How are you playing back these MPEG-1 files? In Media Player?
SonyDennis wrote on 12/6/2002, 12:32 PM
Thanks for the movie, I wouldn't have figured out what you meant without it.

Which file is on the top track (the track that's out of sync when you zoom in)?

As you zoom in, Vegas switches from drawing with the peak data to drawing from the raw audio data from the file. To do this, it needs to seek in the file. It appears as if the MPEG reader is not seeking correctly in that stream.

Based on the fact that other programs also mess up, I'm guessing the headers are corrupt and therefore the seeks are failing to end up in the right place.

My recomendation is to place the entire file on the timeline and render it to a good format, like DV. Then, use that file to render just the part you want. Rendering from the start like this will reduce the seek problems.

Perhaps use Batch Converter (comes with Sound Forge), if you have it, since it will try to seek less during rendering.

///d@
ibliss wrote on 12/6/2002, 10:23 PM
"How are you playing back these MPEG-1 files? In Media Player?"
The audio from the origianl MPEG-1 plays back perfectly in Vegas and Windows Media Player.
The rendered MPEG-1 has sync problems when played back in both Vegas and WMP.

"Which file is on the top track (the track that's out of sync when you zoom in)?"
The MPEG-1 Video & associated Audio track are at the top, the Rendered WAV files is the lower of the two audio tracks. It is the rendered WAV which is out of sync.

"...It appears as if the MPEG reader is not seeking correctly in that stream."
So is this to do with a setting within Vegas - one that I could change?

"...I'm guessing the headers are corrupt"
Is there a utlilty that can fix this, or is it un-repairable?

"My recomendation is to place the entire file on the timeline and render it to a good format, like DV. Then, use that file to render just the part you want...."
I have tried this with both MM and Vegas (I used the NTSC DV template) - the audio of the rendered DV file was still out of sync.

"Perhaps use Batch Converter...."
I tried this, but it failed to complete the render - it stopped at around 4% (version 5b).

Thanks for your suggestions so far. I will continue to work on this one!
Mike K