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Mastering Audio Level
I’ve been working as a TV producer for a local TV studio for about 5 years now, but I’ve always been very confused by audio mastering levels. I come from the digital audio world, where I produce a lot of music in my home studio, along with doing some quick mastering for redbook standards. In that case, at the end of the chain, I limit and normalize to 0dB, which all professional CDs and mp3s are leveled at (well, within -.5dB). In the digital world, 0dB is a very obvious limit because there is no headroom. However, when I look at SMPTE standards, -12dB is thrown out as the standard limit. Wait… what? What does -12dB mean to a DAC? Absolutely nothing. Why isn’t the standard 0dB as it is everywhere else in the digital audio world?
At my TV station, we have a end-chain limiter/compressor set at a 3:1 ratio at -9dB. Forever, I’ve been mastering at -6dB, and allowing the last 3dB to get a bit of last minute limiting. This seems to be a no-no to SMPTE standards, but I find that if I master to -12dB, then my TV spots are much quieter than the other spots on our airplay system.
Is this just archaic remnants from the old analog standard, in which there you had headroom? Why is everything so complicated?
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2 Replies
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Your digital audio world is still intact … you are safe at 0db. I just finished a documentary in which there were almost 80 interviews, and it was placed in a 2-DVD case, both DVDs were dual layer DVD-9s … over 4 hours of material, and it all sounded extremely crisp and sharp … of course, all interviews were shot with a Schoeps CM4 mic, a very sweet sounding mic … so don’t sweat setting your levels at 0db. Trust your ears more than technical specifications.
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Keep in mind that digital levels don’t register certain levels in the same way that analog will. The reason for the lower digital levels is that you can set digital peak for zero, but there will still be analog peaks above zero in many circumstances.
I typically set digital tone in PPro to – 12… I try to generally keep the audio levels there as well. When I have to make an analog recording to beta sp for instance, I’ll set the record deck to tone at 0. Any levels that create spurious peaks for analog that didn’t register for digital seem to be handled by analog headroom…
For many digital delivery specs, I’ve seen -20 specified. With digital, reduced level means reduced resolution so I tend to wince at actually delivering -20.
As is said around here quite often, your mileage may vary.
TimK,
Director, Consultant
Kolb Productions,
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