limiter function on audio...

newmediarules wrote on 9/14/2013, 12:48 AM
i am clearly missing something here.

i'm looking at a project on my vegas timeline. it has two separate audio tracks; one voice, one music.

i also have a limiter filter on the master mix. appears to be working fine. no "peak" problems, etc.

the client wants a copy of the music track and voice track, separately. i render them by soloing the tracks on each render. still no problem (as far as i know).

i run a "test" on the new music and voice files. meaning, i placed the new audio files in a new timeline and played them together with no filters whatsoever.

and to my dumbfoundedness, i see peak problems here and there. why? and how do i fix this?


Grazie wrote on 9/14/2013, 1:19 AM
Just check to see if you've got any "doubling-up" of the audio? Or that which you monitored previously was too high but you'd reduced the output to compensate, and now that anomaly has "surfaced".

Check to see if any Volume Envelopes are raising the volume. Maybe by soloing you've isolated not only the content but also the limiting.

Really scrutinize your Timeline and Mixer for that anomaly. It's got to be there.



farss wrote on 9/14/2013, 2:30 AM
First off check that you have Audio Resampling set to Best. A number of times I've noticed the audio meters are not 100% accurate at anything other than Best.

Aside from that I would entirely expect what you're seeing to happen.

You've limited the sum of two tracks which is different to limiting each track and then summing them.

Grazie wrote on 9/14/2013, 2:35 AM
I've caught myself out before now doing the limiting - AND I'll do it again.


farss wrote on 9/14/2013, 2:52 AM
Quite apart from the confusion what the OP is doing is not wise and may not avoid clipping, it'll just mask it.

For example, if I sum two tones which are at 0dB I get +6dB which is clipped. Add a limiter and it'll knock the clipped tone back to 0dB so it reads OK on the meters but could sound pretty bad. With program it's harder to notice this happening.


newmediarules wrote on 9/14/2013, 3:06 AM
fars, i am convinced you are absolutely correct. but how do i approach a solution to my dilemma?

my ears are quite good. i was doing sound recording long before anything video. i only say that to say this: i don't hear a problem with these files, but i see the peaks. but obviously, i can't turn in audio with peak violations.

i hate to adjust volume after i have a good mix. it, in my experience, takes too much of the punch out of the mix.

what would you do?
farss wrote on 9/14/2013, 5:18 AM
Given that your intent seems to be to produce two audio files that can be simply added via a mix and not go over then first and foremost I'd go to the theory. That says both tracks must never exceed -6dB because if they do then it's possible two peaks can coincide and added together exceed 0dB.

How I'd wrangle that is by adding two busses and routing the two tracks to them. I'd then apply brick wall limiters set to -6dB to the busses. Reason for working that way is so the limiters are applied after anything I'm doing at the track level. At the same time while I'm mixing I'd keep an eye on the levels going into the limiters on the busses.

I do this kind of thing a lot when I have to deal with music I've recorded live with fast transients in it from drums. I often use a fast limiter before a compressor to get some punch without the risk of going over.

Laurence wrote on 9/14/2013, 8:53 AM
There is a built in brick wall limiter in Vegas called "Wave Hammer" but I have never liked using it. A while back Waves was running a sale on their plugins and I picked up their Ultra Maximizer which I just love. Really good for taming those odd peaks that would otherwise clip if you didn't bring the overall level way down.
musicvid10 wrote on 9/14/2013, 9:24 AM
Bob's got the right idea. Track volumes are additive, and aggregate peaks need to be in range before any limiting or processing.
A limiter of any flavor is not a gain control . . .
rraud wrote on 9/14/2013, 8:27 PM
A limiter of any flavor is not a gain control
+11; no pun intended.
Excessive limiting can add distortion.. especially some limiters like Wave Hammer's secondary stage, which can sound extremely good if applied judicially. Most limiters these days however were/are designed to squeeze the life out of tracks and win the 'louder is better' award.
farss wrote on 9/14/2013, 8:55 PM
[I]"There is a built in brick wall limiter in Vegas called "Wave Hammer" but I have never liked using it."[/I]

The Track Compressor has two presets that make it work as a limiter.
The "Soft" limiter preset will not catch fast transients which can then get past the attack time of a compressor.

I'm no fan of limiters either however when dealing with drum hits around 20dB above program that'll go straight through my compressor taming the transients and fattening them up a bit helps keep my mix sane. Most likely the OP would not strike this problem, certainly not with his premixed music track.

musicvid10 wrote on 9/14/2013, 9:46 PM
With today's 150dB mics, "some" limiting during live recording is essential, lest the average gain come out way too soft, effectively raising the noise floor and reducing available bit depth. Some engineers add light compression during recording as well, but I've never liked the result in post.
Laurence wrote on 9/15/2013, 12:22 AM
Whenever I can I record at 24 bits, normalize, then dither down to 16 bits. That gives you a true 16 bits.