Sync problems when converting to .ac3 from .mp3

[BrianK]

I have a XVID file of a TV show episode that has the .mp3 audio file as VBR. When I open it up in Virtualdub, it tells me:

"Variable bit rate audio detected. VBR audio in AVI is non-standard and you may encounter sync errors up to 6358ms when attempting to extract WAV files or processing the audio in Direct Stream Copy mode. Full Processing mode is recommended to decompress or recompress the audio. (bitrate: 130.6 +- 21.0kbps)"

I used Full processing mode to extract the WAV file, but when I try to convert it to .AC3 and then mux it back in with the video, the audio is still out of sync. Any suggestions on how I should be handling the audio so it syncs with the video?

Thanks,
Brian[/img]

[guns1inger]

When you set the mode to full processing, did you also make sure that Uncompressed PCM was picked ? How big was the resulting wav file ?

[celtic_druid]

How did you encode the AC3? You could try ffmpeg since it can convert directly from the avi.

[AlanHK]

I have a XVID file of a TV show episode that has the .mp3 audio file as VBR. When I open it up in Virtualdub, it tells me: "Variable bit rate audio detected...."

There are some versions of Virtualdub that can handle VBRs, eg Virtualdub_MP3_Freeze.
But (if not editing the video) I find it simpler to extract audio separately, using BeSweet (with the Wizard interface). It can use an AVI as source and create an MP2 directly (unfortunately, AC3 export is a bit buggy, so take care, the volume often comes out very low).
Media Coder can do this too, and can do AC3 properly, but it's a bit more complex to use.

To stop Virtualdub complaining about audio, just tell it to ignore it: use an AVS script like:
AVISource("07.avi", audio=false)
and proceed to encode the video.