Audio sync problem

[JackT]

Hi there

You see, I have this problem. I have a couple movies on mpg that I want to convert to Divx and I keep getting this audio sync problems.

What happens is that after the conversion the audio is not the same lengh as the video. So far no big problem. It is always by the same amount, so I use AVI Information to strech the video until it is right. I even know how much I have to do each time, because it is always the same.

However, when playing the film, it starts perfectly in sync but begins to lose it as the time goes on. If I stop the film, fastforward to where I was and restart playing, it is in sync, but will start losing it again.

My guess is that it has something to do with the interleaving, but I use the same (default) setting in virtualdub that I do for DVD ripping, where I never get any problems at all.

Any ideias about what could be the cause or what interleaving settings to use?
Could it have something to do with converting from a NTSC frame rate (on the mpg) to PAL frame rate (on the avi)?

Thanks

[Enchanter]

"Could it have something to do with converting from a NTSC frame rate (on the mpg) to PAL frame rate (on the avi)? "

Yes. You should never alter the frame rate of the video file. Off-synch audio always results from this kind of tampering.

[JackT]

I'll try without the change in framerate, but since it's being reencoded i'm not sure it could explain the progressive loss of sync during the playback...

[Enchanter]

"it could explain the progressive loss of sync during the playback..."

Changing the framerate of the video does not mean that the framerate of the audio will accordingly change. 25 fps video muxed with audio meant for framerates of 29.97 fps will obviously result in what you are now experiencing.