Nesting To The Rescue

Nesting to the rescue

In a previous post, I recounted a problem I ran into when I tried to match an offline sequence to a finish or online sequence. Basically, the camera originals were very long and had been trimmed because it wasn’t feasible to render out color-graded full-length clips. I tried to duplicate the edit using those trimmed clips.

When I compared the graded, speed-changed clip to the original speed-changed clip, they didn’t line up. Even when I was able to line up the first frame, throughout the clip there were frames that didn’t match. In my post, I mentioned that I solved the problem by nesting. This post describes the process.

The problem was caused by how edit software calculates which frames are displayed when there’s a speed change. While I don’t know the exact methodology, I believe that the calculation always starts with the first frame of the clip. All of the math proceeds from there.

For example, let’s take a hypothetical speed change that involves playing two frames, skipping one, playing one, dropping two, playing two, skipping one, playing two and then repeating. You could represent that sequence as 11010011011, where 1 represents a frame played and 0 represents one that’s skipped.

At first 11010011011 seems like an unreasonable sequence (or cadence). However, if you work with something shot at 48 fps or 60 fps that’s inserted into a 30p or 24p sequence and is sped up to fill a hole in the sequence – say 148 percent – you might see why the cadence could end up like that.

“So what?” you say? The problem is that the cadence always starts with the first frame of the clip. That means when the new color-graded (and trimmed) clip starts on a different first frame, chances are excellent that the frames displayed and skipped won’t match.

How about dragging the new clip around and getting it to match? No. It won’t match—unless you get lucky and the starting frame is a multiple of the cadence and matches up with the old clip. It won’t take Clint Eastwood to ask you about your luck, believe me.

A fix I found was to use nesting. Nesting allows you to group one or more clips (typically laid out vertically in a sequence) into a new sequence that then gets edited into the original sequence.

  • The first step is to take the original (long) clip that’s used in the original sequence and make that clip its own sequence. Make sure that the sequence uses the entire original clip from the first frame to the last.
  • Note that I don’t use the “nest” command on the clip in the timeline because it would create a nested sequence of just the part of the clip that’s displayed. Remember that the cadence starts with the first frame of the clip, not just what’s displayed.
  • In this new sequence, I create a second video track and place the trimmed clip into that track, matching the timecode. Since no speed change is applied, the clips will match throughout the duration of the trimmed clip.
  • Now I take that new sequence and lay it over the original clip in the original timeline. There are two ways to match the timing of the two clips.
  • Apply the speed change and then line up the timecode by dragging the clip, or
  • Remove the speed change from the original clip, line up the timecode and then apply the speed change to both the original clip and the new clip.

Either way, the new clip now matches the original one. Why? Because of the nesting, the cadence is dependent on the first frame of the nested sequence. And since the first frame of the nested sequence is the first frame of the original clip, the cadence is the same.

While nesting has a lot of different uses in an edit, it really was the only way to solve this problem.