Audio Levels/Compression For TV at DVinfo.net

Glynn Morgan · December 6th, 2010, 04:33 AM

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!

David Stoneburner · December 6th, 2010, 10:21 AM

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.

Seth Bloombaum · December 6th, 2010, 10:49 AM

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.

Adam Letch · December 7th, 2010, 09:27 PM

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

December 6th, 2010, 04:33 AM	#1
Glynn Morgan Regular Crew Join Date: Feb 2009 Location: Australia Posts: 119	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!

December 6th, 2010, 10:49 AM	#3
Seth Bloombaum Inner Circle Join Date: Sep 2003 Location: Portland, Oregon Posts: 3,420	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. __________________ 30 years of pro media production. Vegas user since 1.0. Webcaster since 1997. Freelancer since 2000. College instructor since 2001.

December 7th, 2010, 09:27 PM	#4
Adam Letch Major Player Join Date: Feb 2006 Location: Perth, Western Australia Posts: 414	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

December 6th, 2010, 10:21 AM	#2
David Stoneburner Major Player Join Date: Jun 2003 Location: Orlando, FL Posts: 494	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.