Found a workaround for Vegas time stretch audio artifacting

DCV wrote on 1/8/2004, 1:14 PM
I recently discovered a nice workaround to eliminate artifacting in an audio clip I had to "compress" to sync correctly with some video. The audio was captured from an analog input at 48k from a Minidisc.

First, get the audio synced up correctly with the video. Chose a sync point towards the beginning of the clip. The earlier in the clip, the better.

Then go to the end of the audio event. Grab the end of the event, hold down the ctrl key, and "compress" it until the audio is synced up across the entire video clip. I like to do this while the clip is playing in Vegas. It works really well and allows you to hear the results as you adjust the length of the clip.

Here's where the work around comes into play. If you leave the adjusted clip as is, depending on the amount of compression, you will have noticable artifacting in the audio. To fix this, go through the audio clip and every few minutes or so, at a place preferrably where it's quiet, press the S key and split the audio. Then right-click on the section of audio to the left of where you just split. Select "Properties..." and bring up the Properties dialog.

On the bottom of the Properties dialog is the Method for the Time Stretch / Pitch Shift. Depending on what you have set in your preferences it should say "Change length, preserve pitch" or "Change pitch, preserve length". Change this setting to "None" and press Okay.

What you'll notice is that the section of audio will revert to its original length and will very slightly overlay into the next section. Keep splitting and changing the Method property to "None" for each section until you reach the end of the clip.

What we're doing is analogous to taking the original clip, cutting it up, and slightly overlaying the sections end-to-end to compress or remove time from the whole clip. I've found the technique works great and is pretty easy to do in Vegas.



farss wrote on 1/8/2004, 2:22 PM
If the problem is just the sync drifting then I'd always strecth the video in preference to altering the audio or else remove a frame here and there from the video to avoid resampling it.

I've done this quite a few times, it can be a bit of work though.
jeremyk wrote on 1/10/2004, 11:01 AM
Thank you, John, for that elegant solution. A good fix for a real problem!