Progressive Audio Desync

Fixing Progressive Audio Desync

Introduction

This guide is for fixing progressive audio desync in your source files, that is if the sound starts out synced but gets more and more desynced during the course of the video. This is not a guide for videos that have been incorrectly appended in VirtualDub(Mod).

For AviSynth users, here is a much simpler method.

Tools

For this guide I will use VirtualDubMod, Media Player Classic and Audacity. Any other programs with the same functionality should work too.

Ripping the sound

If the sound and video is in the same file start up VirtualDubMod and load the source file. Go to Stream -> Stream List, select the audio stream and choose Save Wav. If the sound is in a separate file make sure to convert it to wav if it is not. If you need a converter dBpoweramp has support for most sound formats, just search the codec list on their site.

Fixing the desync

Load the saved wav in Audacity. Then play the source file in VirtualDubMod and listen at the end and check the time to see how much off the sound is in seconds. Then go back to Audacity and press Ctrl+A to mark the full length of the sound and under Effect choose Change Tempo and under Length (seconds) change the length of the sound with how much the sound is out of sync. If the sound is slower than the video, shorten it and vice versa. Then go under File and choose Export as Wav. Save the file under a different name.

Then open Media Player Classic and choose Open File. In Open choose the video file and in Dub choose the edited sound file. Now check at the end and see if the sound is in sync. If it is, go to the next step, otherwise reload the original sound file in Audacity and change the tempo again. Changing the tempo on the edited file repeatedly might lower the sound quality so always do that on the source file.

Using the edited sound

If you're encoding in VirtualDubMod load the source video and go into Streams -> Stream List and choose Add to add the edited sound file. If the original audio stream is in the list, disable it.

For use with AviSynth just create a script file with the line

wavsource("K:\Path\To\Fixed_Audio_File.wav")

and load it in MeGUI to convert the sound to the formats required.