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Audio: -3db or -4db Hard Limit Problem

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Scott Clements
Audio: -3db or -4db Hard Limit Problem
on Feb 6, 2013 at 12:00:56 pm

Hi,

I have been looking for a solution for this forever. However, when I look on the net, the only answers I get are A. There is a hard limiter in FCP, called either the compressor/limiter or aupeaklimiter (neither of which seems to work the way it's supposed to) or B. Larry Jordan says to use Soundtrack Pro.

However, when you're trying to make a program for a user who only has Final Cut Pro installed, how do you make a program for him that will play in his final cut pro system that does not exceed say -3 or 4db? I can't figure out any way to do this. All I can get the compressor to do is squash the dynamic range, but no matter how hard I try, I can't get it to act as a limiter. And the aupeaklimiter only seems to prevent sounds from going over 0db (and it only appears to be able to do this on nested audio, not individual clips). There doesn't appear to be any way to make a hard -3 or 4db limit. The documentation on these tools is really poor. Does anyone know how to use any of the tools in Final Cut Pro (excluding Soundtrack Pro) in order to create a hard limit of -3db. A detailed description would be very much appreciated. Many thanks if you're able to provide an answer.

Sincerely,

Scott

Film Editor, London UK
http://www.scottclementseditor.com


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Sareesh Sudhakaran
Re: Audio: -3db or -4db Hard Limit Problem
on Feb 6, 2013 at 2:50:56 pm

I'm not very experienced in FCP, and you probably know this already, but will the levels slider in the Viewer be of help? You can reduce volume on a shot or frame basis. On the timeline, you can do it in one full sweep.

Hope this helps.

http://www.wolfcrow.com - Workflow information and support for filmmakers, photographers, audiographers and videographers.


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Scott Clements
Re: Audio: -3db or -4db Hard Limit Problem
on Feb 6, 2013 at 4:03:45 pm

Thanks, Sareesh, but unfortunately, it's not that simple. You can go in and adjust levels manually, but to take dynamics into account, it could take you weeks to properly mix a show like that. What I need is a hard limiter, so that I boost the overall volume and anything boosted too loudly, gets brought down to an acceptable level. Both Premiere and Avid have hard limiters that make sense, but I've never ever been able to figure out if FCP is even able to do this. Other people on the net have the same problem, but no proper solution been given except using soundtrack pro, which is difficult to use in my situation.

Film Editor, London UK
http://www.scottclementseditor.com


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Matt Lyon
Re: Audio: -3db or -4db Hard Limit Problem
on Feb 6, 2013 at 4:18:20 pm

Scott, I've also struggled with this over the years and you can get decent results using the compressor/limiter filter. But you won't find a "one size fits" all solution, because how audio filters behave depends entirely on the nature of the source material. But hopefully I can give you a starting point:

1. nest your audio tracks (or, better yet: "bounce" them to disk, by exporting your timeline to a self contained AIFF file, using FILE>export>using quicktime conversion)
-You may want to do this step to your whole timeline, or just your DIALOG and SOUND FX, because music tracks are usually heavily compressed already.

2. Apply the "compressor/limiter" filter.

3. IMPORTANT: Turn OFF the "preserve volume" option. This is critical. If you leave this option on, then FCP will basically just BOOST your quiet sounds to achieve dynamic range compression. If you turn this option off, then FCP will lower (aka attenuate) the loud sounds in order to achieve dynamic range compression. With the "preserve volume" on, FCP is doing what other programs call "auto gain"; the result is your levels are just as hot, so no audio limiting is effectively taking place.

4. Now you have to dial in the settings to get the proper amount of attenuation. Start with a very low threshold (-6 to -18). You only want the filter affecting the loudest sounds. The exact setting you use depends on the peak levels of your source material, so every program will be different.

5. Now set your "Ratio." This is the amount of attenuation applied. I don't know exactly the relationship between this number and dB, but I /think/ that "-2" equals 6 dB of attenuation. So that is a good starting point.

5. Now adjust the attack time and release time. I start with 0 attack and maximum release (4000) (because you want the filter to be "on" all the time). But this can sometimes create too much signal limiting. Use your ears and find the settings that suit your material. But I usually stay with "0" attack, and never go below "200" for release, but YMMV.

6. Now that you've tamed the dynamic range of your program, you may want to apply "normalization gain" (Modify > Audio > Apply Normalization Gain). This will let you actually set a "hard maximum" for your audio level. I've found the number I enter in the option box doesn't seem to create the expected results, so some fudging may be required. Normalization gain works MUCH better after you've compressed your dynamic range, by the way.

7. If you've left your music tracks unfiltered, you may now need to give them a global volume adjustment in order to "sit" better with the rest of the material.

Matt Lyon
Editor
Toronto


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Scott Clements
Re: Audio: -3db or -4db Hard Limit Problem
on Feb 6, 2013 at 4:56:35 pm

Thanks, Matt! That's all great advice. I was applying normalisation gain first, and then compressing, which was making things quite difficult. Hope all's well in Toronto - my home town!:-)

Film Editor, London UK
http://www.scottclementseditor.com


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