I love movies. Old ones, new ones, long ones, short ones, good ones and, sometimes, even bad ones.
Movies usually include people and they tend to talk to each other, so somebody has to edit the dialog track. Dialog editing is an interesting balance, simultaneously serving the needs of the visuals, the story and the soundtrack. So, whether you're editing Citizen Kane II or an infomercial for the Bulge-Buster, a quick dialog-editing refresher won't hurt a thing.
It Starts In the Field
We won't spend too much time on this point, but here's a reminder: editing clean dialog begins with recording clean dialog. This isn't as easy as it sounds. Indoors or out, there are virtually no silent environments anymore. Inside, you have to deal with air conditioners and other mechanical systems. Outside - even in the middle of nowhere - there are bugs, birds, planes and wind. All these things change over time. Therefore, the close-ups you shot this afternoon probably sound different from the master shots of this morning. These differences can come back to bite you during editing. While you can't control nature, you can control microphone choice and placement. If the setup requires a shotgun mic, get it as close to the subject as possible and maintain a consistent distance and angle throughout the shoot. If you're using lapel microphones, pick a location - hidden or visible - and stay with it 'til the end of production. In either situation, a closer position will buy the most isolation from extraneous noises. This makes editing easier and uniform.
Back In the Cutting Room
Everyone edits differently and each project has its own dynamic, but I usually like to start by dropping a master or establishing shot on the timeline to get the flow of the scene. Before you go any further, here's a time - saving tip - apply the filters you know you want now. This way, when the longer clips are sliced into short clips, you won't have to apply the same filters over and over again. Let's say our dialog was recorded outdoors with a shotgun mic. Since the audio is only on one channel, we want to add a "Fill Left" filter (or "Fill Right" depending on what channel your recorded dialog lies) to spread the sound across the stereo sound field. Second, to minimize wind noise and stray rumble, we'll insert a "High Pass" filter, setting the cutoff frequency to somewhere between 90Hz and 120Hz. Finally, let's normalize the entire clip, boosting the volume consistently throughout the file without going over the maximum level. As you carve this clip - with these touch-ups in place - each piece will fit better with its brothers and sisters. This technique isn't as helpful with shorter clips, but it works great on longer takes.
Movies and television would be pretty dull without cutaways, inserts or POV (point of view) shots. Of course, this means another take with another setup. Then, multiply that by the number of people in the scene and you could have several alternate views of the same setting - all with potentially different audio. First, find a place in the master shot that begs for a cutaway. Next locate the perfect POV and drop it on the timeline above the master. A simple razor cut to trim away the master shot and your insert is up and running. And don't forget to apply the same audio filters and normalize the clip to unify the sound with the master shot. Trimming and re-trimming the results will tighten the overall performance. All this slicing and dicing could leave some noticeable gaps, which you can cover with natural sound or room tone. Room tone is the name for the background "silence" sound in your recording environment. You can capture this sound with whatever mic you're using. Use room tone where there are gaps in dialogue to get seamless sounding environments. It's best to record the sound with all the talent and crew in the room, because that's how the dialog was recorded, instead of in a completely emptied room where you might pick up some hollowness or an abandoned vacant feeling.
Not all cutaways contain dialog. Sometimes a look or facial expression is all you need to tell the story. In these cases, you need to use a pair of audio editing techniques called the J-cut and the L-cut. The J-cut preserves the visuals of the first clip, inserting audio from a second clip. In this way the audio corresponding with the second shot of the split edit proceeds and falls under the first shot of the split edit. L-cuts work the other way: it uses the audio from the first clip then proceeds to fall under the second shot of the split edit. Think about an on-screen telephone conversation. If you simply cut back and forth as each person talks, it ends up looking like a ping-pong game. Using L and J-cuts, you can still hear one person on the phone, but see the reaction of the other, and vice-versa. You can perform these custom cuts several different ways, but the easiest is to use the Rolling Edit tool. In Premiere Pro, simply mouse over the split, hit the "n" key, select and drag your mouse across the video track. The overlap is automatic. It takes some practice to master, but this technique gives your piece a more professional look and makes it easier for the viewer to watch.
Even after painstaking filtering and normalization, your dialog track could still use some polishing. This is where we exit the edit program, so save your dialog track as a WAV file and open it with your audio-editing program. If you hear a lot of background noise - possibly changing with each edit - it's time to do a noise reduction pass. Noise reduction filters are not always included in editing software, but are an incredibly useful tool if used in the right instances. Even the most professional noise reduction tools can be of no use if you can't isolate the noise. If done right, however, it should make your dialog stand out while minimizing the amount and difference of noise. If the dialog sounds muddy and dull or bright and thin, it's time to apply an equalizer to shape the tone of the piece. Boosting deficient frequencies and cutting prominent ones will help smooth the rough edges. You can even apply custom EQ touches to specific areas of dialog to repair serious problems. Finally, use a compressor or limiter to even out the volume differences in the edit. Three to six decibels of gain reduction across the entire piece should smooth it nicely. When you're done, save the file and import it back to your editing program and once it's on the timeline, mute the other audio tracks and preview your finished cut to verify synchronization.
Dialog editing is a skill unto itself. It shares many of the disciplines of standard editing and audio editing, and many of these techniques can be used while editing voice-overs too. Regardless of what you're editing, it all takes some practice, so get busy creating your very own conversation piece.