[ This article was first published in the November, 2008, issue of
Larry’s Final Cut Pro Newsletter. Click here to subscribe.
Updated Jan. 2009, and Jan. 2012. ]
I love audio. I love recording audio, mixing audio, and talking to engineers about audio. But if there’s one thing I’ve learned its that if I get five audio engineers in the same room at the same time, I’ll get seven opinions on what qualifies as good audio levels.
Yet, good audio levels are essential to any video project. So, in this technique, I want to talk about two things:
NOTE: This article was written for Final Cut Pro 7. But the concepts described here apply to setting audio levels on all NLEs on both Mac and Windows.
ORGANIZING YOUR AUDIO – or – THE BENEFITS OF CHECKERBOARDING
When ever you edit audio into your Timeline, you have to put it somewhere. My philosophy is that since you have to store it, why not store it in a place where you can easily find it.
Even better, why not store it in the same place for each project. That way, when you open up an old project, you don’t need to wonder where everything has been put.
When I first started editing with Final Cut, I took it as a personal challenge to make sure there were NO empty holes in my audio tracks. I edited audio like it was a jigsaw puzzle. No two clips went in the same place, or even on the same track.
I was feeling pretty proud of myself until I needed to reedit a project I finished about six months earlier. It took me almost four days to figure out where I put all that audio!
Organizationally, it was a complete shambles, and it cost me days of time to figure it out well enough to fix it.
I realized then that there had to be a better way. There is — its called checker-boarding — and I stole it from the movies.
Here’s the basic idea: Put the same audio on the same track. Though Final Cut audio is not track-based, both Soundtrack Pro and ProTools are. This means that if you ever plan to send your audio out for professional mixing, they will first take the time to checker-board your audio — which costs you both money and time.
Plus, when you decide to start mixing your own projects, checker-boarding will save you time.
To summarize the benefits of checker-boarding:
Audio engineers have been checkerboarding their projects for years. In fact, my system is modeled after many that I’ve seen used in professional audio suites — where mixing a major motion picture soundtrack can have over 100 tracks of audio!
While I don’t expect you to be mixing an audio project that big, we can still follow the same procedures. So, here are the rules I follow as to what audio goes on which track. Feel free to borrow this for your own projects:
Audio Track Allocations
1 and 2 — Sync sound — what news calls Sound-on-Tape (SOT)
Your main speaker, the audio from the image on V1. I now put all the male voices on one track and the female voices on a second track. This allows me to add EQ effects by track.
3 and 4 — Sync sound — what news calls (NATSOT) The sync audio from B-roll images on V2
5 — Narration. One voice needs only one mike, which needs only one track. If I have male and female narrators, I put them on separate tracks.
6, 7, 8 — Sound effects. Sound effects (SFX) that you buy are mono. SFX that you record yourself are most often stereo. Assigning three tracks means that you have room for all of these. Add more tracks as necessary.
9 and 10 — Music cue 1
11 and 12 — Music cue 2. Putting music cues on separate tracks allows you to slowly fade out one piece of music, while rapidly fading in a new piece of music.
I always follow this track allocation during editing. If, for instance, I don’t have a narrator, then I just pull up the lower tracks. However, I make a point to never combine different audio on the same track. Sound effects are never placed on the same track as sync sound.
The most important rule to remember with audio is that your audio MUST NOT EVER go over zero. Not once. Not even a little bit. Not even when no one is looking. NEVER!
The red clip lights must remain dark for your entire project.
Unlike analog audio, digital audio starts distorting as soon as your audio levels exceed zero and those red clip lights flash on. While you are mixing, these red lights tell you that your audio levels need adjusting.
However, during final output, those red lights indicate that your audio has been permanently damaged and there is not a technology on the planet that can fix it. You’ll need to go back to your source materials and remix.
IMPORTANT POINT: Final Cut only displays audio levels as peaks. Peak measurements provide far higher levels than measuring RMS or “average audio levels.” FCP uses an audio scale called “dBFS” or “Decibels Full Scale.”
There are only three technical offenses that will get an editor fired:
1. Audio levels that go over 0 dB.
2. White levels that exceed 100%.
3. Chroma levels that over-saturate.
Of these, the easiest to prevent is maintaining control over your audio levels. (Keep in mind that no one, really, cares how soft your audio goes — that is an aesthetic decision you get to make. Technical problems only exist when your audio gets too loud.)
However, audio sounds better when it is loud than when it is soft. So our goal is to get as close to 0 dB as we can, without going over.
Note: Here’s another little-known audio factoid — audio levels are logarithmic. Every time your gain increases by 6 dB, your volume doubles. This means that when your levels are hovering around -6 dB, you have as much audio gain between -6 and 0 as you do between -6 and -96. -6 dB is the 50% point for your audio levels!
So, here are levels that I recommend for all general mixing — creating audio for DVDs, the Internet, broadcast, weddings — anywhere that there is not a specific technical specification that you need to meet.
Audio level we must not exceed: 0 dB
Total audio mix level: -3 dB to -6 dB
Principle speaker (SOT) audio: -6 dB to -12 dB
Sound effects audio: -12 dB to -18 dB
Music when its an underscore: -18 dB
Use these levels as a guide to get your audio levels close. Then, use your good speakers, your good ears, and your good common sense to make your audio sound perfect.
Remember, the only level that counts is the level of the total mix.
Note: Don’t confuse reference tones with audio levels. Reference tones are used to make sure audio levels match between various pieces of gear. They do NOT determine the maximum point of your audio levels.
I’ve found that these levels sound great when used for DVDs, web video, and general purpose broadcast.
Note: Many broadcast commercials are mixed to a level of -10 dB, with no dynamic range. Again, if you are given specifications for your mix, please follow them.
THOUGHTS ON OTHER AUDIO MEASURING SYSTEMS
You sometimes see references to dBFS. This refers to how audio levels are measured. Final Cut uses a dBFS scale. However, that is not the only way we have to measure audio levels… that would be too easy.
In the UK, they use an entirely different audio measuring system called PPM. There’s a very useful Final Cut utility called PPMulator+ that displays PPM levels inside Final Cut projects. Generally, PPM levels between 3 and 4 are considered appropriate.
In Europe, they use dBU.
Older, analog systems use VU (Volume Unit) measurements.
As I was researching this article, I got a very helpful email from Woody Woodhall, of Allied Post Audio in Santa Monica, and head of the Los Angeles Post-Production Group. Woody writes:
These systems are all measuring the same thing. What’s confusing is the dBU and dBFS. The dBU looks to me to be modeled after analog metering which goes into the “+” range and dBFS is absolute and stops at zero. The formula to convert from one to the other is:
0 dBU = 4 PPM = -18 dBFS = -4 VU
[Depending upon project] levels for broadcast delivery are:
+8 dB = 6 PPM = -10 dBFS = +4VU
Like video editing, audio mixing is both art and science. But it need not be a mystery. Using these settings can help your projects sound great — while keeping you on safe ground technically.
UPDATE – Jan. 7, 2009
Bob Merrill adds:
I wanted to add one thing regarding audio levels. If you are using Compressor to make MPEG-2’s for your DVD’s, make sure and set the “Dialog Normalization” to minus 31. Failing to do so will result in a final audio level lower than expected.
Larry replies: Thanks, I’ve mentioned this before in other training, but am happy to add it here.
UPDATE – Jan. 7, 2009
Woody Woodhall sent me an illustration of the mess we’ve made of audio levels. He writes:
If [you are creating a project] for broadcast my experience is that the “peak” levels delivery specs are either all over the place or non-existent. In December I delivered a commercial to [a large] cable [system], I asked for their audio specs. They sent me a very nice sheet that had a lot of information regarding the video and a sentence that said “Program Left should be Channel 1 and Program Right should be Channel 2.”
I then called, found a master control operator who told me to “do whatever you usually do.” So much for standards…
Larry replies: Thanks. I’ve also gotten a couple of emails expressing confusion over being told to set program levels at -20 dBFS. Because audio is logarithmic, setting program levels this low means that you are using less than 12.5% of your total audio dynamic range. This makes no sense to me! However, I’m doing some more research and will supplement this report if I find anything that needs revision.
AUDIO COMPRESSION FOR THE WEB
UPDATE – June, 2010
Recently, I was talking with the tech support folks at Aphex, who make high-end audio gear for network and broadcast work. They told me that MP3 files are optimized for a maximum audio level of -6 dB, while AAC files are optimized for a maximum audio level of 0 dB.
Since much of the audio work that I do gets compressed into both formats, I’ve lowered my audio levels a bit so that they are peaking between -6 and -4.5 dB.
My audio still sounds good and I get nice clean results when compressing to MP3 files.
(For the record, almost all my encoding is the spoken word, as opposed to music, and I use a data rate of 56 kbps for MP3 compression of mono audio files.)
Based on this, when I normalize clips, I’m now normalizing to -4.5 dB. I also use the same level settings when using the Limiter filter in Soundtrack Pro.
FINAL CUT AUDIO METERS
I’m sure I mentioned this somewhere, but, if not, just a quick note that the audio meters inside Final Cut measure audio peaks on a 0 dBFS scale. There are other audio measures, such as PPM in the UK and Europe, and average level meters, which can be added to FCP.
So, if you are confused, as I was awhile back when talking with an audio engineer who wanted to mix all the audio to -20 dB, while I wanted to mix it a LOT higher, remember that average audio level and peak levels are not the same thing.
Regardless, remember that your audio levels still can’t go over 0 dB. Not even a little.
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