Working with Nests
Nests are sequences referenced by a single clip contained in another sequence. To create a nest in your current sequence, you highlight a selection of clips (possibly all of them) and press Opt+C or select Sequence, Nest Item(s). When you invoke the Nest Item(s) command, a dialog box opens for you to name this nested sequence. This nested sequence appears as a new sequence in the Browser window, creating a nest in your current sequence.
Nests can be used for a variety of purposes. A common use is to lower the numbers of video and/or audio tracks contained in a sequence for easier navigation. Another use of nesting sequences is to add audio and video filters or transitional effects to the entire set of clips contained in them. You can also use nests to repeat a sequence of shots within the same sequence. If you change the nested sequence, all instances of that nest change simultaneously . Rendering the nested sequence forwards this render into all instances of the nest.
If you drag a sequence to another sequence contained in the Timeline window, it appears as a single clip. When you double-click a nested clip, it opens the sequence it references in the Timeline window and displays itself in the Canvas window. Any changes made to the nested sequence are reflected in all occurrences of its nest (the single clip that represents it). As long as these single nested clips were not copied from another nested clip, they are unaffected by changes to the original nested sequence.
Any time you want to repeat sequences of clips you might want to change en masse, you must drag from the Browser or edit from the Viewer the nested sequence to a different sequence in the Timeline. If you copy the nest itself (the single-clip reference of the nested sequence) and then paste this copy again in any sequence, changes in the original sequence are not reflected in these copied single-layer nests. In other words, if you drag a sequence to a sequence, the nest corresponds to changes in the first sequence. If you copy the single-layer representation of the nested sequence and paste it into the same sequence or another sequence, changes in the original sequence are not reflected in these copied nests.
When you click a nest in a sequence and press Enter (or Option-double-click the nest), it opens in the Viewer to allow you to add and modify effects. For example, you might want to fade up an entire composite of many layers. By changing the opacity of a nest in your sequence, you change the opacity of all the layers contained in it at once. You can change all the Motion tab settings for a composite in this manner as well. Another example of using a nest is when you want to change the size of all the clips and position them as a group . This technique lets you add a letterbox effect to an entire sequence. Or you can reposition the clips on the screen to add text to the side of a picture-in-picture effect, which could be a series of clips or a composite of some sort .
You can also use nests to preserve renders . You can create a separate sequence for intensive composites, for example. When you add these rendered sequences to your main sequence, they maintain the renders even if you change the nest's In and Out points. However, you cannot add time to the In and Out points past the duration of the clips as they are edited in it, nor can you add the same sequence to itself. It's best to create a new sequence for this sort of work. You can create a sequence and add it to another sequence as many times as you want.
For example, you can place in a nest intensive effects done to a composite, render them, and then apply effects to the nest. This allows you to control how and the order in which the effects are applied. In other words, the effects applied to the nest affect all the clips in it after the individual effects are applied to those clips. You might want to add border or color correction to the entire nest after you have added a filter or composite mode to the individual clips contained in the nest.
You can also put nests inside nests. Using this technique, you can overcome the limitation of layering only 99 tracks of video on top of each other, but each nest can have only 99 tracks of video. Chances are this is enough for any project.