Velocity Envelopes - using them on a track with audio

kungfujoe wrote on 2/13/2003, 4:43 PM

I initially posted this in the Audio Topics forum, but it seems equally related to video. I hope posting a question in two equally relevant forums (fora?) isn't too heavily frowned upon here.

This seems like a simple problem, but I can't for the life of me figure out how to do it in Vegas. I simply want to use a velocity envelope on an audio track. In theory, this should be simpler than doing it on a video track, especially if I'm willing to do it without preserving pitch. However, I can't find any indication that it's possible to either use a velocity envelope on audio, or use a velocity envelope on video and lock the audio so that it stretches with it.

With as many functions as Vegas has, it seems like this has to be possible.. But how?

Comments

EPsymp wrote on 2/13/2003, 6:17 PM

I failed to find anyway to do it. I know it'll work with scrubbing but i don't know if you can somehow manipulate that to render at different speeds. Good luck, sorry I'm not much of a help at all.

DataMeister wrote on 2/13/2003, 7:00 PM

You can hold down the CTRL key on a PC keyboard and stretch or compress an audio clip. I think it tries to perserve pitch when you do this.

However, the properties box for a clip gives an option to set whether pitch is preserved or length is preserved in Time Stretch/Pitch shift. I what this drop down list relates to.

There are also two plugins that can be used. Time Stretch and Pitch Shift. But then of course that ignores the simplicity of a velocity envelope.

JBJones

kungfujoe wrote on 2/13/2003, 10:42 PM

The problem with the Ctrl-Stretch is that it stretches the sound linearly. That is, if the end result is twice as long as the beginning result, the audio clip plays at 50% speed, even though my video velocity envelope may smoothly slow down to 1/4 speed, go back to 3/4 speed, back down to 1/4 speed, and then back to full speed, or something along those lines. That is, stretching the audio like this doesn't correctly account for the transition time. Another example would be if I wanted to slow from 100% to 0% in a linear fashion over the course of 3 seconds. I think this would use 1.5 seconds of footage. The video would be following the envelope, continuously slowing down, until it stops. But the audio would play at 50% speed the whole time.

Hopefully I'm explaining more clearly what I'm looking for. Is it impossible with Vegas? Is it possible with any existing software tool? It seems like such a simple effect, to the point where I could probably write a C program to do it if I had the proper libraries, and if I could come up with a mathematical function to match what the Vegas velocity envelope is doing.

jetdv wrote on 2/14/2003, 8:28 AM

There is no velocity envelope for audio. To do that you will have to export the audio to some other program. Using CTRL-drag will change the speed of audio but it will be a constant speed change.