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Audio Metering
by
Larry Jordan
[This article was first published in the February, 2009, issue of
Larry's Final Cut Pro Newsletter. Click here to subscribe.]
Here is a dialog between Rich Roddman and Woody Woodhall about last
month's article on audio levels. Woody is a professional audio engineer,
president of Allied
Post, and president of the LA Post-Production User
Group.
Rich Roddman writes:
Thanks for another great newsletter. I always learn something new.
I just want to be sure I understood your article on the audio measuring
formula you received from Woody Woodhall.
If I have the tone in my Edit to Tape set at -18 and I am recording
to a analog deck such as a Beta SP, if I read this right
I should set the deck's VU input levels to -4 for correct calibration?
I have always found setting meters in FCP or Pro Tools out to analog
meters confusing. I ALWAYS check playback for distortion or over-modulation.
And it seems when ever I try to find a correct ratio I get different
answers from the station engineers where I send my spots.
Any clarity in this area would be grateful.
So, I sent Rich's questions over to Woody Woodhall who
wrote back:
Rich - Just curious why you are using -18 as a ref tone. We have found
that in the crazy world of audio specs (which seem to have no rhyme
or reason) that -20 in the US is the standard. Are you submitting to
Europe or is this for the US? I will sheepishly admit that I haven't
looked at a VU meter in years but in times of yore (OK a few years
back..) we would calibrate -20 dbfs tone to 0 on the VU meter.
If this is for broadcast my experience is that the "peak" levels
delivery specs are either all over the place or non-existent. In Dec
I delivered a commercial to Time Warner cable, 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...
Rich writes back:
Thank you for your time in this matter. To answer your question over
a year ago we (the post house I work for) switched to send our broadcast
and cable spots via DG Fastchannel. To do so you first have to be approved
by there engineers for quality control. The video was fine but we were
failing for audio. Their engineer told me that their rules are the
baseline of the file should playback at -18 db with the peeks being
no more that +6 db over that. So I remixed the test spot in Sound Track
Pro using the method I learned from one of Larry's seminars using normalization
and limiters. Then in Final Cut I need to drop the timeline -6 db before
exporting the file and compressing in Encore. That was the formula
that got me approved for DG. Thinking consistency would be a good thing
I reset the output of my Final Cut system to -18. The broadcast stations
here in the Tampa area still want spots on beta sp and it is more cost
effective send an intern that via DG.
I will set my system to -20 since that won't effect what I do for
DG.
Woody concludes:
The crazy thing here is that we are three working, experienced professionals
and still here we are scratching our heads! Europe uses -18 as a ref,
US -20 as a ref, some gear comes with a default -12 as a ref... and
then the frame rates craziness... so much for our technological improvements...
All the best,
Larry wraps up: And who says that video engineers should be the only
ones confused about standards?
Larry Jordan is a post-production consultant and an Apple-Certified Trainer in Digital Media with over 25 years experience as producer, director and editor with network, local and corporate credits. Based in Los Angeles, he's a member of both the Directors Guild of America and the Producers Guild of America.
The information in this article is believed to be accurate at the time of publication. However, the author assumes no liability in case things go wrong. Please use your best judgment in applying these suggestions.
The opinions expressed in this article are solely those of the author. This newsletter has not been reviewed or sanctioned by Apple or any other third party. All trademarks are the property of their respective owners and are mentioned here for editorial purposes only.
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