audio out of sync in converted file, but good in original avi file

[ibzomie]

I have an avi file that I converted to mpeg2 for DVD, changing the audio from 44100Hz to 48000Hz, using Main Concept.

The original file seems to be perfectly in sync from start to finish.

The converted file seems to be a tiny bit out of sync even at the very beginning, and by the end is way out of sync.

Am I doing something wrong? Maybe missing a setting or something? Does changing the resolution from 512x384 to 352x240 have any effect on the audio?

[redwudz]

The first thing I would check for is MP3 VBR audio in the AVI file. That can cause exactly your problem. Saving out the audio as a WAV in VirtualDub and converting it separately is what I do in that case. I convert it to AC3 next with ffmpeggui then add it back in when authoring. Or you can mux it back with the video.

The video frame size has no bearing on sync. The condition you describe with the sync error is usually caused by the audio and the video having different running times.

[ibzomie]

I opened the file with G-Spot, and I see nothing referring to VBR. In the audio section, under CODEC, it says "0x0055 (MP3, ISO) MPEG-1, Layer 3." Directly underneath that is a small blue box with the numeral 1, and another small box that says "OBR." Nothing about MP3 VBR.

Would it be worthwhile to go ahead and save out the audio with Virtual Dub anyway?

[guns1inger]

A poor quality upsampling can also sometimes change length - does the audio seem different in pitch after the conversion ?

What is the runtime of the video and audio after conversion ?

[ibzomie]

The pitch seems to be the same to me, but I'm not known for being able to detect exact pitch or anything.

Where do I look to find the run time of the video and audio? I've looked in G-Spot, but I don't see anything that looks like it's telling me that. Am I missing it, or am I looking with the wrong tool?