This is a short piece on how to correct OOS (Out Of Sync) issues that are constant, i.e. the Audio is not in sync with the Video (or still images) and it is constant - the degree of OOS does NOT drift over time, but is always the same.
While it is written for use in PrPro, it works in PE, as well.
Imagine that we have one Clip in our Video Track (VT) and one Clip in our Audio Track (AT). We realize that our Audio does not match up to our Video. Words do not match the lips in a Close Up (CU), or a drum beat occurs before, or after the stick/mallet hits the drum.
The first thing that I do, especially if the sound on the AT comes after the visual in the VT is to add about 02 sec. of Black Video (via the New icon at the bottom of the Project Panel>Black Video, and then trim it to 02 sec. in the Source Monitor) to the Head of the Video Clip. More on this later. Now, we find a good audible and visual key. If we shot a clapper/slate at the beginning of the scene, we’re home free. However, we seldom have a clapper/slate, so we need something else. Let’s use a CU of someone speaking for the visual, and the words that they speak for the audible keys. Look closely at the CU of the speaker in the VT. Find a word being formed, that we recognize. Place an Un-numbered Marker at that point. Also, compress the Work Area Bar (WAB) to cover a few dozen frames before and after that Marker. Watch closely and listen carefully to the footage under the WAB. Does the Audio come before the Video, or after it? If it comes before, then we know we’re going to slide the Audio-only to the right. The Black Video, that we added will not come into play. More often, the Audio is after the Video, and this is why we added that Black Video.
We have the Marker over our visual key, and the WAB set to the area around it. Turn OFF Snap (s key toggles it), as we want to be able to freely move the Audio without it interfering with our movements. Zoon in on the Timeline so that we can both see it clearly and to restrict our next movements to much smaller degrees. I also vertically expand the VT and AT to see both the Video and Waveform display well. Look at the Waveform display for the Audio and try to find that point where the word, or sound is displayed. Alt-click on the Audio Clip. This basically "un-links" it from the Video on a temporary basis. That is what we want. While still holding down the mouse key, slide the Audio to the left (or right depending on whether the Audio precedes, or follows the Video). Unfortunately, when we go to slide the Audio, the Waveform display greys out. I’ve made feature requests to have the display NOT change, as is would make this action so much easier. I try to Alt-click on the spot where the Waveform display indicates the sound. Slide to get that point under our Marker. Release the mouse button, and watch carefully and listen closely. Are the two now in sync? If not, are they really close? Have we now shifted the OOS from after, to before our sync point? Alt-click again and nudge the Audio in the appropriate direction. This can take a bit of time, but the Zoom-in on the Timeline gives us pretty fine movements. Continue to adjust, and then play/listen. Each time that we release the mouse button, the Audio re-links to the Video. Finally, we have re-established sync.
Now, hit the Home key, to get to the beginning of our Clip. If the Clip that we are working on is not the only Clip on the Timeline, hit the PageUp to go to the Head of our Clip. We will address the Black Video now. If our Audio preceded the Video, we just remove it. If our Audio followed the Video, we now will have some of the Audio beneath the Black Video. That is why we added it, to allow us to freely move the Audio to the left. Depending on what the Audio Clip contains in the space that it is beneath the Black Video, we might just be able to shorten the Audio Clip to the Tail of the Black Video - basically setting a new In Point for the Audio. If it is something important, then we have a little problem in that we have no Video to go with it. There are a couple of thing that we can consider. The first is leaving the Black Video in and adding a Dip-to-Black Transition. between it, and the beginning of our Video. This is in effect, a "J-Cut." We will hear the Audio, before we see any Video. The Audio is heard, and then the Video fades up from black. The use of both the J-Cut and the L-Cut (the opposite, where we see the Video, before we hear the Audio, is a very effective means to add some drama to the edit. If you have never explored either of these techniques, now is the time to do so. They slightly disarm your audience and lead to heightened expectations. Here, we’ll assume that we can just re-set the Audio’s In-Point and then can delete the Black Video.
Look closely at the Head of the Audio Clip. You will see a number with either a "+" (Plus sign), or a "–" (Minus sign). Make note of this number, as you will use it for all of your additional OOS Clips from the same source, i.e. with the exact same OOS issue. If it’s not perfect for any more Clips, it will be very, very close, saving you time, as you’ll use it as your "starting point," to establish sync.
Now, turn Snap back on (s key toggles it), or you’ll miss it with later editing. We’re done.
If your OOS issue does drift over time. You can use the method above to correct it, but we’ll likely have to cut the Clips into smaller pieces with the Razor/Scissors Tool. As you can see, we’ll then be working on short "snippets" of our original Clip. This can become tedious, but with patience and careful viewing and listening, one can correct all but the worst drifting sync problems. If you are working with drifting sync, you really do need to consider those J & L-Cuts, as you’ll likely need to use them.