In the last post we took a look at the fundamentals of working with Elastic Audio in Pro Tools.  Elastic Audio is the powerful function that allows you to stretch and compress audio like a rubber band, all without changing pitch or rendering any new audio.  The main focus of this function is in the music world, allowing you to quantize your music performance to the beat.  In post, however, Elastic Audio has quite a lot to offer.

Here we’ll take a look at what it can do for ADR sync, one of the most important aspects of post production sound editing.

So let’s say you’ve tracked some ADR for your show, as in this example:

Here the original guide audio from the show is the top track (green) and the ADR is on the second track (red).  You can see that the waveforms are close, but clearly they don’t entirely match in terms of sync/timing.  We’ll use a combination of traditional editing techniques and Elastic Audio to correct for this.  First let’s just shift the ADR to the right a bit to get that first syllable in sync:

So that helped with synching up the first syllable, but now the back end of the clip is even further out of sync.  Let’s use Elastic Audio to fix this.  First we’ll need to instantiate the Elastic Audio plugin on our ADR track.  Remember, that’s done by using that single dedicated insert point on the Edit Window, right below the automation mode and voice selectors (in the above picture it’s the light-grey bar with the triangle on its left side).  We’ll choose the polyphonic engine.

Next we’ll flip that track into “Warp” view via the Track View Selector (where it currently says “Waveform”):

Now we’ll place a warp marker on the first event marker that Pro Tools has identified (hold control and click on the event marker with the grabber tool), which will serve as an anchor for our stretching, locking that point on the timeline so that all stretching we do is relative to that point.

Then we’ll add another warp marker at the last event marker, and we’ll use that as our main tool for squeezing the ADR in order to make it match the guide audio better.

Now, using the grabber tool, we’ll drag our last warp marker over to the left until the ADR waveform most closely matches the guide audio waveform.

Now the ADR will much more closely match the sync of the original set audio.  If we want to finesse things further, we can always add more warp markers and adjust the relative position of the syllables to get things even closer.

The best part is that we can just keep playing around with the timing of these markers until we get the results we want, all without waiting for any rendering or processing.

Once you’ve completed your ADR time stretching and editing and you’re ready to send things to the mix stage, be sure to remove the elastic audio plugin and commit your changes.  Just go to the Elastic Audio Engine selector (where it currently says “Polyphonic”) and choose “None – Disable Elastic Audio”.

Pro Tools then gives you the following prompt:

Simply choose “Commit” and Pro Tools will render new audio that has your stretching applied to it!  Now you can turn over your tracks to the mix stage just like anything else, knowing that your ADR adjustments have been applied and will be retained.

Elastic audio has tons of other great uses, and we’ll look at a few in future posts.  Stay tuned!