Nonlinear Editing, Like Digital Asset Management, Requires Metadata

NLE - editing video using metadata. In a previous life I was a video editor for a company that pioneered nonlinear editing systems. During that time, I used to collaborate on edits with a very talented editor located in Maryland (I’m located in Massachusetts). In order to work together we had to devise a workflow where we could both edit the same video project. Keep in mind that in the early 90’s most people still were using dial-up, and moving large media files over the Internet was completely out of the question.

For those of you unfamiliar with the video world, here is very brief overview of how it works: “Nonlinear editing systems” (NLE’s) edit video in a non-destructive manner, meaning the edited sequences are just a series pointers back to the full media files (as in “start at this timecode and end at that timecode”). During an edit, the original media is never actually changed – it’s all just the manipulation of metadata – the metadata holds all of the instructions about the edit. When editing, the metadata of the sequence changes to reflect new timing, new sources and details on the visual effects. Much like in digital asset management systems, metadata is the key to making the system work.

As part of our collaborative workflow we decided to use this to our advantage. At the start of the project, I would digitize all of the media. The early 90’s also pre-dated widespread adoption of digital video (DV), so all of our tapes had to be converted from analog component video into motion JPEG files. Once all of the media that we could possibly ever need was on a hard drive, I would copy the hard drive and send the duplicate drive down to Maryland. I would also send a copy of all the bin files which included all of the metadata about each video clip – the tapenames, start and stop timecode, number of tracks, video and audio formats and all the other pertinent information.

As we began editing, we’d both be able to work off each other’s edits by emailing the modified bins with sequences (the metadata) back and forth. These bins were generally very small (a couple KB or so) and were very easy to email. The only time we’d need to send actual media files would be if either of us generated a title. The media files associated to the title were still as small as 1MB and could easily be emailed. It was best if both systems were always sharing exact duplicates of all media, including titles.

The trick to this type of collaboration was making sure that we had the most current sequence before making any changes. If one of us was to begin editing a section of the video based on a previous version of the cut, there would be problems – problems we had to deal with in a couple of instances. Since I would be mastering the final sequence, it usually meant I had to backtrack and rebuild my changes into the sequence I had received. If the timing had changed between the previous and the current version of the sequence, I would have to re-cut the changes from Maryland, to make them fit within the current version.

Once we had the picture locked down, I would prepare and master the sequence for the sound edit. Sound prep meant adding a frame of white 2 seconds before the start of picture. This flash was called a 2-pop and was used to synchronize the finished sound once it was received. Mastering was taking the sequence (that had up until this point just been metadata) and converting it to a single Quicktime movie file. The music and sound tools would work the same way as the video editing tools – manipulating small metadata files until the project was complete. When the sound was complete, they would add a sound blip to correspond with the 2-pop on the video, master to a final media file and send it back. The final step in completing the edit was to lock the picture and sound together using the 2-pop.

Without metadata this workflow would not have been possible. This data that describes the media we work with is essential in post production just like it is in digital asset management.

Posted by James Burke

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