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Old December 6th, 2010, 04:33 AM   #1
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Audio Levels/Compression For TV

Hi,

I made a small community service announcement that will be going on local television. But first I must have the TVC approved and the guidelines are a bit perplexing. Of the 3 years I did film and TVC production at university, I never came across this (part of classifying a commercial):

*Commercials must be preceded by a one kilohertz tone having a constant
relationship to and representing the normal level of the audio material that
follows it.
For analogue systems, the alignment signal will be used to equate the
audio level of the material to the stations’ recording and transmission level
of zero VU. In digital systems, the alignment level will be 20dB below full
scale digital and will be equated to zero VU on the station audio level
meters. The reference level (line-up level) must be minus 20dB with
respect to the onset of digital clipping i.e. –20dBFS (SMPTE RP.155).*

What does this mean? I don't want my audio levels to be too loud, I have heard I should mix it so it peaks at -10 dB, it's just a simple voice over track with a music backing track. Should I limit the audio to not go over -10DB, is there a way to apply this? What is -20DBfs, vegas has no mention of DBfs anywhere.

Cheers!
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Old December 6th, 2010, 10:21 AM   #2
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Basically it's digital audio vs. analog. Set your tone to -20db and then make sure all your audio is set to that, with peaks just over -20db. All they are doing is making sure not to have the audio clip. Professional formats like DVCam and DVCPro use -20db for their tone level. You'll find that most consumer cameras use -12db. Just adjust everything to -20db and you'll be fine.
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Old December 6th, 2010, 10:49 AM   #3
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Location: Portland, Oregon
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Yes, peg your tone at -20db in Vegas.

For program averages and peaks, it really is a local question, not one that should be answered from across an ocean.

Rather than mixing too hot or too quiet, you might just call up one of the station engineers and ask where your audio should peak and average.
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Old December 7th, 2010, 09:27 PM   #4
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once you've done the above

when you export your clip, use the option to have colour bars, which will automatically include your 1k sound signal for a ref level
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