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Audio Tips for Video Editors

Audio Tips for Video

Most video editors are so "into" their craft, they jump right in to all things video. But their mind is usually on the eye candy. They can get the audio basically in and out of the project, but don't know enough or have the tools to do any real audio manipulation.

The first big mistake I see in video editors is editing with headphones. Do not, I repeat, do not mix with headphones. Although editing with headphones seems to be an accepted practice in video circles, I don't think any serious audio editing to video should have headphones involved, ever. To which Jacquie responds, "Be realistic. What about the editor on a deadline on an airplane or with a sleeping baby in the next room?" OK, but avoid headphones at all costs whenever you are able. If you need to use headphones, only use them to get a general idea of the quality of the audio and whether it is in sync with the video. Don't do any volume adjustments or mixing of audio channels. Headphones give a false representation of the amount of noise in the program material and don't give a fair or accurate representation of the frequency or spatial characteristics of sound.

Get a good pair of monitor speakers and use them exclusively. Try to mix and edit on the same speakers when possible – you want to get to know the particular characteristics of your mixing/monitor speakers. Most video professionals think nothing of investing in all of the tools to edit great video. Computers, drives, convertors, generators, switchers, and software are purchased, and the list continues way past anything that I'm familiar. Then comes the audio tools. Believe me, I've seen Radio Shack equipment. And what about that long line of speakers sold in the Apple Store? Jacquie again, "What about the new indie filmmaker with no money? What's wrong with inexpensive speakers?" Consumer speakers are tuned to make audio sound good, to eliminate noise and distortion and to enhance your listening enjoyment. You can use them to identify and fix major flaws and distortion, but not to fine-tune your audio. Consumer speakers are probably adequate for internet-only and low-end event and beginning documentary and fiction films. For professional editing, you should have professional near-field reference monitors that are designed to allow you to hear the flaws. They don't put out a lot of volume, so set them fairly close to you, equidistant and no more than a meter apart. Put them ear level or unobstructed on your desktop.

Jacquie stole my favorite small Genelec's for her video system long ago, and has patiently let me speak my piece on investing in good equipment as penance. Now she is hounding me to get back to real-world editing issues. The first problem she complains of is timid editors who don't turn up the volume enough to really hear the audio. You need to listen with the volume high enough to hear the nuances of the sound – too loud and the speakers will distort; too soft and you might as well have on headphones.

A related problem with new editors is misinterpreting the sound volume coming out of the speakers. This might sound contradictory, but it's not. Change the speaker volume and you change what you hear, but you didn't do anything to the sound in your video. A sad example is the would-be editor who kept bumping up the sound in Final Cut, not realizing that she had the output sound turned down too far in her computer. She had already generated a DVD with a heavily distorted sound track when she came to Jacquie for help. Use the meters in your video editing software to set overall audio levels, not your headphones or speakers. Audio levels on a finished video should peak at -4 to -6.

A couple of basic tips for editing a single track of audio: If you need to change the volume, make the change over as long a period of time as possible, and put the beginning and end keyframes at audio peaks. Before and after an audio peak, the volume changes a lot, so your change will be hidden in these other changes. If you change the volume rapidly during a quiet period, your listeners are much more likely to notice the change and feel that it is artificial. Below are examples of a good edit and what to avoid. Also, crossfade audio between clips whenever possible to reduce sound artifacts.

Examples of good & bad audio edits

Mix a voice as a mono signal in the center. When mixing several channels of sound, mix in order of importance. For example, if you have a voice and music, usually the voice is more important and should be louder than the music. Usually set separate tracks at different volumes to indicate their relative importance and minimize sound clutter. When mixing audio from a multi-camera shoot, review what microphones were used and where they were located before mixing, possibly using a track sheet -- use this to help decide what channels to use or not to use or which to mix and at what levels. (Remember, these are helpful generalizations for a beginning editor when mixing more than one audio source. These might change quite a bit if working with a seasoned audio engineer.)

Modern video editing programs come with lots of audio filters, a confusing number in fact. To complicate things even further, similar results can be obtained through different combinations of filters. Below are a few important filters that video editors ought to be familiar with and able to use when necessary:

  • High pass (or low cut) filter: This filter allows the highs to pass so that you can reduce the lower frequencies. This is useful in reducing breath and wind noise, reducing microphone or boom pole handling noise, and rumbling vibrations in the bass.
  • Low pass (or high cut) filter: This filter allows the low frequencies to pass so you can reduce the higher frequencies. This is less common but can be helpful to cut out hiss and reduce overall noise.
  • A lot of video editors also use the Vocal DeEsser and Vocal DePopper filters. I don't use these because I prefer an outboard compressor/limiter, but these are more advanced and expensive and most commonly found in the audio engineer's toolbox. (Vocal "pops" can also be minimized by a piece of hardware that clamps on the mic stand and is between the voice talent and the microphone. It looks like a circle around 8 inches in diameter covered with pantyhose. But, it isn't practical if the talent is on camera before a large audience.)
  • Gain filter: If your video editing program will only let you boost your volume by a limited amount, and you need to boost it more, try adding a gain filter. Most professional video editing software comes with accompanying audio software, and it the volume increase from gain filter increases noise too much, you may end up needing to get to know it so save your audio.

Note from author, Kraig B. Greff
"OK folks, I have to admit I was kind of pushed into this one by my wife Jacquie. But to be fair, my little brain was a blank slate as far as good ideas for an article. She then told me of a few audio mistakes made by her editors and asked if I could write something basic that might help them."

Kraig & Jacquie Greff, authors