The offline/online workflow allows you to use temporary, reduced-quality copies of your footage to edit with, and then finish your project with full-quality media. Reduced-quality media files require less hard disk space and less computing power to process transitions and effects. This means you can edit on an inexpensive computer or a portable computer and then finish at full quality on another system. Once the creative cutting is complete, the online editing phase (also referred to as the finishing phase) focuses on image quality, color correction, proper broadcast video levels, and so on.
The two phases—offline and online editing—are connected via an Edit Decision List (EDL), or other project interchange file, which is used to transfer all of your editing choices from the finished reduced-quality session to the final high-quality session.
Editing with reduced-quality copies of your media files allows you to fit more media on your scratch disks and improve playback and real-time effects performance (especially when using slower hard disks, such as in portable computers). This phase can last from a few days to several years, depending on the scope of the project, the amount of footage, and so on.
Edit Decision List or Other Project Interchange File
When the edit is complete, you can export all of your edit decisions for use on another editing system. Older editing systems use a relatively simple text format called an EDL, while newer interchange formats, such as OMF, AAF, and the Final Cut Pro XML Interchange Format, describe many more details of your original sequence.
Online editing, now better known as finishing, starts with an offline project file or a project interchange file, which describes the media you need to reingest at full quality. Online editing actually has very little to do with editing in the traditional sense. Timing, storytelling, and fine-tuning your edits should be complete in the offline editing phase. Online editing focuses on image quality, color correction, maintaining broadcast video specifications, detailed effects work, titles, audio levels, and so on. Compared to the offline editing phase, an online edit session goes very quickly (anywhere from a day to a week), and generally requires more expensive equipment.
Important: It is critical that you maintain accurate timecode, reel names, and file metadata for keeping track of where footage is located in both tape-based and file-based media. Make sure you log clips and label tapes and other media carefully so that you can reingest footage at any quality at a later time.