Editing a narrative feature is difficult enough. The logistics of it have the potential to be frustrating–the clips aren’t labelled well enough, so you can’t find that one shot you really like, and when you do find it, you can’t use it because Character A’s hair isn’t the same as in the rest of the scene. There’s a dinner scene where Character B’s eyeline is off, but you can’t cut it because then the rhythm gets thrown off and Character B’s confession to Character C in the third act makes no sense whatsoever. By the end of dealing with all the footage you have to, somehow, end up with a movie.

Well, imagine editing a movie with no script, a movie where you didn’t even know what sort of footage you’d be getting because it’s all user-submitted. And that footage? Imagine there being 4,500 hours of it. Those were some of the challenges faced by Joe Walker, editor of Life in a Day. The documentary, executive produced by Ridley Scott, consists of footage shot by people across the globe as they went about their lives on July 24, 2010. The movie debuted on Sundance, with a simultaneous screening on the film’s YouTube channel (http://www.youtube.com/lifeinaday).

Joe Walker took the time to answer MovieMaker’s questions on the challenges posed by editing Life in a Day.

Rebecca Pahle (MM): How did you get involved with Life in a Day? It’s different from other film you (or most people) have edited; what made you want to work on something so massive?

Joe Walker (JW): I was introduced to [Life in a Day director] Kevin [Macdonald] by Liza Marshall, our producer. Some time ago I cut a film called Eroica for Liza, [which is about] a day in the life of Beethoven; the day just happens to be the day of the first rehearsal of the Eroica Symphony, the day when classical music changed forever. I’ve worked mostly on drama, not documentary, but Liza knows just how much genre-busting projects like this one appeal to me. And my background in music helped swing me the job, I think, as Kevin anticipated a big collaboration between the cutting room and the composers.

What made me want to work on something so massive? Megalomania, probably. I wanted to see if I had it in me to manage a big team, far bigger than any I’ve dealt with in the past. And something about the very real danger that we might not find a film out of all the submissions got my pulse racing. I think it’s a good sign when you not only long to join a project but also develop a fear of it.

MM: You combed through around 4,500 hours of footage–did you have any expectations before you started watching about what sort of content you’d get and what themes you wanted to explore in the finished film?

JW: We set up our team on an estimation of 12-15,000 clips, under a thousand hours of footage, but by the end of July that figure had reached 81,000 clips and 4,500 hours, so we were anticipating a lot less content altogether, that’s for sure.

Kevin’s an intuitive film-maker, a doer, so there were few preconceptions. He made the analogy of not wearing ourselves out pointlessly machete-ing our own way through the jungle. but to go with it and look for natural pathways to open up. However, the decision to ask certain questions was intended, I suppose, to provoke certain discussions. Our attitude to possessions, say. That one also provoked great time capsule material.

In any event, one could always rely upon millions of coincidences and rhymes in this material, just because of the sheer volume and range of it. So when we had to move big chunks of the film into a different order, and had to lose connections we’d begun to rely upon, we knew that other connections would swiftly take their place. Some of those only dawned on us later, such as how two very different contributors utter the words “because I’m a man,” or how many clips feature a space where a mother should be.

MM: How did you decide what footage to use? Would you like to do anything with any of the footage that was left out?

JW: There were certain themes that popped out at us, and it was just a question of picking which clips would do the theme justice. For example, we spotted endless shots of people shooting their own feet walking, so it felt inevitable we’d work with that material at some time.

Another example : One of the early tagwords the researchers coined was “mybeautifulgirlfriend” which was used to signify any clip that featured a keen photographer filming his girlfriend, often backlit in a park, usually in the first flush of romance. Everyone would look out for this strange subset of clips knowing that at some point we might combine that with other subsets to create a chapter on relationships.

Personally, I loved all the shots of silly pompous men irritating their long-suffering partners. Luckily that amused Kevin too, so we got to it, building up what at first was an almost hourlong cut in which you followed the stages of a romance as if of one couple, but sewn together like Frankenstein.

I feel tremendous guilt about all the shots we had to jettison. Especially with all the trouble people went to in order to provide release forms and upload their originals. But we could only make one film, out of the hundreds of possible films one could indeed make. Luckily we didn’t have very long to dwell on this because our cutting period was only a few months long, all in all.

We often talked about a 24-hour Life in a Day, something more like an art installation than a feature film, perhaps something like Christian Marclay’s brilliant “Clock” at the White Cube gallery. I heard that YouTube has commissioned visualisation whizz kid Aaron Koblin to work with all the uploaded video, so I’m dying to see what he’s come up with there.