Setting -12db for on air. Need advice at

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Old October 9th, 2009, 02:36 AM   #1
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Location: Australia
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Setting -12db for on air. Need advice

I have a TV show edited in FCP that needs to go to air and the TV station requested the audio be set to -12db. Most of the audio is floating around -12db with a few peaks hitting -6db. I have a quicktime master of the edit.

What is the best way to compress the audio so no spikes go above -12db.
Going back into the edit is impossible as I only have the quick time.

What can I use in STP?
I was thinking adding some compression or limiter to squash the peaks down.
But Im having a hard time as the whole level of the track changes.

Need some advice if there is some around. What do you recommend as a quick fix?

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Old October 9th, 2009, 03:05 AM   #2
Inner Circle
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I'm assuming that they're working on the broadcast - 8db below peak reference tone, which means that when this reference level is set at the usual - 20 db on broadcast digital audio they peak at -12 db. The -12db to zero being just headroom in case people go over the peak level during recoding. Analogue tape handled these over loads very well, digital doesn't, hence the headroom.

I'd lower your final delivery mix level by 8 dbs, so you don't peak above - 12db.
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Old October 9th, 2009, 11:43 AM   #3
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Try the Normalize function, set -12 db, and see if that gives you a good result. /Battle Vaughan
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Old October 9th, 2009, 03:30 PM   #4
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I think what they're asking you to do is bring the level down a bit. Your peaks at -6dB are way too hot for SD broadcast. You need to have peaks bouncing around in the -14 to -12 range with a brickwall limiter set at -10 dBFS so nothing ever goes over that level.

PBS sets a good standard and a lot of broadcasters follow their example. From the PBS Redbook specifications...

3.1.2 Programs are to have average loudness levels
that fall between -28 dBFS and -20 dBFS during the
majority of a program as measured on a digital meter
calibrated to the RMS/VU ballistic. Average loudness
should not go above -17 dBFS at any point during the

3.1.3 Programs are permitted to have audio levels
that regularly peak near but not above the following
limits using a digital peak meter:
SD: -10 dBFS
HD: -3 dBFS.

3.1.4 Programs must be mixed using dialog level
LAeq metering or subsequent ATSC standard
method. They must have dialog levels with a value of
-24 dBFS 2 dB. Programs may have peak music or
effects levels up to the level limits specified in 3.1.3
during moments of dramatic impact, as long as dialog
levels are maintained as specified.
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Old October 9th, 2009, 04:03 PM   #5
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Thanks guys. I have had success with STP.
I brought the file into STP and put a compressor on the track with the limiter setting to -6b, and compressor threshold @-20db this gave me a nice peaks rather than squared off. I then normalized to -12db.
I was struggling to get this working and discovered I needed to Render to Action for this to take affect.
Now the mix is sitting at -12db with no problems.

Simon Denny is offline   Reply With Quote
Old October 9th, 2009, 06:23 PM   #6
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Location: New York
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Simon , are you sure they are not referring to the reference level? Which normally is full scale -20 or -12dBfs (test tone). On the NY side of the pond, normally broadcast submissions must be referenced @ -20dBfs with program audio peaks not exceeding -10dBfs. I have pushed the envelope beyond "limits" on RMS values due to commercial/sponsor client pressure hoping it would be rejected.. it wasn't.
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