Files and Storage Formats - A Practical Guide to Video and Audio Compression - page 292

The Apple iMovie application has this limitation, for example, and you cannot drag
large files (bigger than 2 GB) onto the workspace. You can import bigger files, though,
because the importer will segment the files as they are ingested. When taking the input
directly from a camera or external drive, the files are also automatically segmented at or
near the 2-GB boundaries and a reference movie is created to string them together.
When your project is complete, throw away any unused clips that remain in the clip
bin and tell the application to empty the trash. This is not the same as the desktop trash—
it is video that has not been included in the final edited sequence and that has been dis-
carded. If you have many iMovie projects on disk, clearing out the trash yields a lot of disk
space that would otherwise be wasted.

Empty the trash in your video editing application if it has a trash bin. Lots of
disk space can be wasted by unused video clips that are no longer needed.

Check the manual for your movie-editing software. These applications have many fea-
tures in common and you might find that the same 2-GB file size limit applies to your
application even if it appears to work quite differently from iMovie.

16.8.3 Reference Movies, Play Lists, and Self-Contained Files

The process of editing video involves cutting up the original and creating a new file. Some
editing systems are able to do this non-destructively by creating a play list and storing it
in a reference movie but leaving the original video intact, which means the edit takes up
very little space. A reference movie is like a short cut. It contains pointers to the actual
video, and when you play it back, the video-handling mechanisms in the operating sys-
tem make it appear that you are playing a physical movie. The Apple iMovie and Final
Cut Pro editors are good examples of such systems. They are able to do this so effectively
because they are built on top of the QuickTime platform, which is designed to provide
these services to any application that calls for them.
Eventually, you will want to save the movie as a self-contained copy without any
dependencies (see Section 16.8.4). This will traverse the reference movie and clone the sec-
tions from the physical movies and create a new physical movie. This process will use sig-
nificant amounts of extra disk space. Only the sections of video that are described in the
reference movie will be copied. This would be one of the times when you are most likely
to experience the “Disk Full” message and to have to abort the save. Fortunately, you still
have your reference movie intact, but it is not the time when you are most prepared to go
through your file system and remove redundant material.
There is a very high risk that as you create the space you need, you will remove
something that you will later regret. The risk factor is increased because you will very
likely be doing this 'save-as-self-contained-movie' just before you ship the finished