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Sound Advice: Editing Audio for Video

Sound Advice: Editing Audio for Video

Use a variety of editing techniques to maximize the quality of your video sound.

All too often, video sound takes a back seat to the images on the screen. This isn't just a rookie mistake the big boys do it too. In fact, a television producer once told me that audio was just "that thing that goes along with the picture." I'll never forget his statement; it's an attitude that is embedded in the production culture. With this article, I want you to forget the way you're "supposed" to edit video and think about the sound first. It can change the whole look of your productions and will certainly transform the quality of your sound.

A-Roll, B-Roll

First, let's define some terms. A-roll is a phrase indicating the primary footage in your video. These are must-have elements such as on-camera talent, actors or even your family soccer hero. Shooting the A-roll is critical since if it isn't on the tape, it won't end up on the finished product. The same is true of the sound on the A-roll. Use your best microphones and cables, monitor with headphones and make sure you have spares on hand for critical A-roll audio.

B-roll is supplementary footage that may or may not be used in the finished product. These are filler pieces that reinforce the topic of your video and the words spoken by the on-camera talent. Some examples: traffic movement, a mountain stream, product shots anything related to the main shoot. For this exercise, make sure to record more extra footage than normal. Go out of your way to gather anything and everything to support your video topic. B-roll audio may or may not appear on the finished video as well, but don't use this as an excuse to record sub-par audio.

Another common editing term is insert edit also known as a "c." Insert edits come from a tape editing process, in which video is replaced or inserted in place of primary footage. An L-edit, also known as a split edit, comes from computer video editing and gets its name from the shape of the edits in software. This common editing technique is used in all kinds of video, from news to feature presentations.

Edit for Audio

Most videos tell a story. It may be the story of a romance, a ball game or a salt-shaker manufacturing plant, but every story has a beginning, middle and an end. Using your A-roll footage, capture and import only those clips that tell the story, and then assemble them on the timeline in a logical order. Here's where the fun starts. Imagine we're editing one of those TV magazine interviews a mother's tragic relationship with her oldest son. Normally, we edit for the best possible picture, but this time we're editing the audio portion of the story, not the images. (I'd recommend editing with your eyes closed, but that makes mousing somewhat difficult.)

"But what about all the jump cuts and scene breaks?" I hear you saying. Don't worry about them right now; we'll fix all that later. Your primary objective for now is to tell the story in the smoothest, most logical manner, complete with a beginning, middle and end. First, include the segments that tell about the happy family that used to be. Next, use the clips that describe how the relationship fell apart, and finally, how they resolved the crisis and gained mutual respect for one another.

Snip and Clip

After assembling the rough edit, it's time for a trim. It's possible to trim a video clip in several ways, but the easiest method is your software's built-in trimming tool. Scrub the video to the beginning of the segment you want and, leaving about 1/2-second extra, set the In point on the clip. Scrub to the end of the clip and set the Out point (leaving an extra 15 frames or so). Do the same for all the clips in your video.

Next, overlap the ends of each clip, using tracks 1a and 1b (that's why we left 15 frames on each end). To smooth the switch from clip to clip, use the rubber bands on each audio track to draw small fade-ins and fade-outs. This will ease the transition between clips and provide you a way to quickly eliminate any talk-over. Scoot the clips around as needed, adjusting the In and Out points to fit the new version (if you ever had the "pleasure" of editing video in the tape domain, this feature alone is worth any extra trouble).

Once you're comfortable with the edits, close your eyes and listen to the whole video, from beginning to end. Listen for clumsy transitions, audio glitches and consistent volume, and make adjustments based on your listening experience. If audio volume differs from clip to clip, you can adjust the volume of each clip individually. Using the audio rubber bands on each clip, move your mouse over the clip, hold down the Shift key and click on the center of the rubber band. Now, you can easily adjust the volume based on a percentage of the original volume. Some trial and error is required, but the adjustments are simple to change and undo.

You can also split an audio clip into two or more pieces with the Razor tool. This is a powerful tool that makes short work of stutters, stammers and repeated phrases just cut them out!

Ear Candy

The tools we've used so far are simple hack and slash items that mold our video sound into shape. Don't forget that most video editing software offers other audio tools; many of them sophisticated enough for a recording studio. You can further fine tune your audio with compressor and equalizer plug-ins, adjusting for maximum consistency between clips and an overall smoothness of sound.

If you just can't make it all match up, consider laying a bed of background music under your video. This is an old trick that serves several purposes. The first is obvious it allows you to smooth over the rough edges, drawing the listener's attention away from the unfixable. Second, you can use the music creatively to set a mood. Choose lighter music for the happier segments of the video and slower, more moody music for the tense moments.

But What About the Picture?

The what? Oh yeah, the picture. Once you're happy with the sound on your video, it's time to "fix" the images. If you were careful, there aren't too many glaring jump cuts or visual glitches, but there will still be a few. For simple jump cuts in which the subject is the same but the framing is different, use a simple cross-dissolve between the two clips. This is a classic technique that works well in most instances. If you prefer a more stylish look, try some other transitions, like page peels and pushes. Keep in mind that many 3D effects require a second or two to look natural; your close cuts may not work with this type of transition. Another option is the flash: a technique where you quickly overlap a bright color (usually off-white) for a few frames to bridge the cut. The flash is distracting enough to make the viewer forget about the difference in the two clips. Use this one with caution, it gets old quickly.

To keep it clean, you can insert some of your B-roll material over the cut. Find some B-roll that matches your on-screen topic and insert it on one of the video overlay tracks. Apply rubber bands to fade up and down as needed. This is also a great place to use on-screen graphics such as charts, bullet lists and text.

Fade to Black

Is all this trouble really worth it? Absolutely! Often, it's much easier to repair a handful of video transition problems than to try to fix the sound. Viewers expect the sound to be consistent; we've trained them to watch television since birth. They also expect to see other footage included in videos, so your B-roll "repairs" will not be seen as such. Editing the audio first is a great way to approach almost any video project.

Sidebar: Post-Process Your Audio

You've carefully edited your video using sound as the guide, but there's just something missing. It just doesn't sound like a TV program. Video producers often use audio post-processing to sweeten their video soundtrack. With certain audio software, you can use the same technique. In Premiere, select the timeline, then click on File | Export | Audio. This allows you to export the entire audio program as a single file. Then, it's a simple matter to open the file in audio software and apply some light compression, limiting and equalization. This will fatten the sound of your video with a professional sheen. Back in your video application, import the audio file and place it on a new track. Mute the old audio tracks and you're in business.

Tags:  July 2002
Hal
Robertson
Mon, 07/01/2002 - 12:00am