I have read many forums related to Sharing, but none that I have found have discussed how to only export a selection. They all just assume you want to export the whole timeline.
What is the mechanism by which I tell the program I only want a certain portion of my timeline?
Welcome to the forum.
You can use the WAB (Work Area Bar) to limit the Share of the Timeline for most output formats.
This Tips & Tricks article covers the WAB in more detail: http://forums.adobe.com/thread/869683?tstart=30
I am assuming this is going to be the same for Mac as it is for Windows.
There are two keys to success here.
At the Timeline Level....
1. Setting the gray tabs of the Work Area Bar to span just the segment that you want to export.
At the Export Level...
1. The export choice MUST have an option for "Share Work Area Bar Only", and it MUST have a check mark
next to it.
Are you OK with those details. If necessary, I will go into finer details on setting the gray tabs of the Work Area Bar and pointing to the Share Work Area Bar Only option when available for certain exports.
We will be watching for your progress.
John-- You really could have just said: "Select 'Share Work Area Bar Only'" instead of sending me back to the forums.
Glad that the WAB was the key to your success. It's useful for some other things, besides just limiting the area of the Timeline to be output, as mentioned in that article - powerful little tool, and one that is not immediately obvious to users.
Good luck, and happy editing,