[linux-audio-user] Fwd: [Jamin] Re: soft clip: Achieving Gain, inconsequential overloads

Mark Knecht markknecht at comcast.net
Sun Apr 11 23:43:38 EDT 2004


On Sun, 2004-04-11 at 19:03, R Parker wrote:
>  
> >    My first step, which doesn't effect sound if it's
> > done right, was to
> > simply normalize the tracks up a bit. (I told the
> > normalizer to make the
> > highest peak -1db)
> 
> I've never normalized a track. Can normalization hold
> a -0.5db peak to -0.5 while it pushes a -12db valley
> up to -6db?

No, normalization only scales the data points so that relative amplitude
is maintained. The WHOLE file is scaled so that -3db becomes -1db, -6db
becomes -5db, -9db becomes -7db, etc. This does raise the overall volume
by 2db, but it won't normally get you all that much volume if there are
a lot of dynamics in the file or else you'll clip those peaks.

Normalization is more like an after the fact tweak of the gain control
on the preamp before you recorded. Insted of the people being at -3db,
you can 'turn up the volume' so that same peak becomes -1db.

What you are asking for is exactly what a compressor does, but the way
you ask the question above is in reverse from the way it works. Think of
compression (for now just a single band that covers the complete audio
range) as first raising the valley's from -12db -6db, and then looking
for the peaks and shrinking them down so they don't clip. When the
energy gets too high the compressor 'turns down the volume quickly' (the
attack setting) and when the energy goes down it turns the volume back
up. (the release setting) The 'range' setting is basically the amount
you want to turn the volume down (compress) on the peaks.

In the old analog synth days (and still in the world of analog
compressors) the signal does through a voltage controlled amplified. The
voltage control comes from a circuit that looks at the amplitude of the
input, among other things.


> 
> If normalization behaves that way, it can help
> "louden" a mix which would be appropriate for my
> situation. That combined with cutting dominant
> frequencies would give me the loudness I need.
> 
> I'll read up on normalization tonight. Do we have a
> LADSPA normalization plugin or are they non-realtime
> tools? I imagine you must produce a new normalized
> file. Is that correct?

Yes, normalization creates a new file with new data values. It needs to
be non-real-time since it has to look at the whole track to understand
how to scale all the data values.

> 
> Until this job, I've never really needed to get every
> bit of available gain from a mix so normalization has
> never meant anything to me. Someone on this list tried
> to explain it to me once but I'm to old and bullheaded
> to learn anything new. That is, until my rear end is
> hanging in the air.

I really don't think normalization is going to be all that important to
you in this case. It's more useful (IMO) when a specific track is
recorded low, or came from a source that maybe you didn't have control
of, but it's really nothing more than a volume control. Turn it up too
much and you still get clipping.

> 
> >    I'm no expert on compressors, but I think a
> > 4-band compressor is a
> > really place to start for what you want to do, so
> > Jamin should be
> > helpful. My biggest recommendation would be to
> > compress as little as
> > possible. If I do too much it all sounds unnatural.
> > In my case it's
> > really only the band below 100Hz that's consistently
> > ranging down. The
> > other 3 are moving much less.
> 
> With the job I'm doing compression and limiting are
> probably alot more extreme than what you're doing.
> This is multitrack pop music. Reguardless, when I
> reach for the last bit of gain, I'm limiting to damned
> hard. If normalization does what I hope then it
> combined with leveling the floor by cutting and
> compressing dominant frequencies might enable me to
> achieve greater "loudness" without the super hard
> limiting. As I think about it, I'm not sure what else
> normalization could be.
> 
> Good stuff, thanks for the help,
> 
> ron
> 
> > > 
> > > > --- Steve Harris <S.W.Harris at ecs.soton.ac.uk>
> > wrote:
> > > > > On Sun, Apr 11, 2004 at 10:04:43 -0700, R
> > Parker
> > > > > wrote:
> > > > > > Not sure but I probably mentioned something
> > > > about
> > > > > this
> > > > > > several months ago. Steve, do you have a
> > soft
> > > > clip
> > > > > > LADSPA plug? If yes, I think it should be a
> > > > > candidate
> > > > > > for adding to the output stage of JAMin.
> > > > > 
> > > > > There are some soft clip LADSPA plugins, but I
> > > > dont
> > > > > think any of them are
> > > > > better than JAMin's "boost".
> > >  
> > > > The thing is my client has requested a %20
> > increase
> > > > in
> > > > volume across the entire album. The first
> > question
> > > > is
> > > > does he know what he's asking for. Well, he
> > probably
> > > > has a fair enough idea. He has compared the old
> > > > master
> > > > with stylistically similar million dollar
> > masters
> > > > and
> > > > concluded the percentage to increase.
> > > > 
> > > > If anyone here has tricks for achieving gain, I
> > need
> > > > to hear about them. My bag ain't got alot in it.
> > I
> > > > basically cut dominant frequency either with
> > > > compression or equalization and with the leveled
> > off
> > > > floor, achieve gain possible; input, compressor
> > > > makeup, limiter input, boost and output. Of
> > course
> > > > then it's just a matter of tweaking ratios,
> > > > thresholds, etc.
> > > > 
> > > > The trade off in general is less dynamics and
> > more
> > > > distortion with several deciables of increased
> > > > volume.
> > > > I love the work but this job is like a No Rules
> > Cage
> > > > Match. I might eventually win the title but it's
> > a
> > > > good thing I brought lunch and a first aid kit.
> > > > 
> > > > > I've heard that you can ignore peaks that only
> > go
> > > > > over 0dB for less than a
> > > > > millisecond, but I've not experimented with
> > it.
> > 
> > I think this is very specific to to where in the
> > chain it happens as
> > well as the exact system you're using. 
> > 
> > > > 
> > > > If that's the case, then I might have this job
> > in
> > > > the
> > > > bag. I'm watching overloads at the input
> > channels of
> > > > my mixer flicker on and off. I've been trying
> > very
> > > > hard to have absolutely zero overload
> > indications.
> > > > 
> > > > Any idea how to test this potential point of
> > > > flexibility or how to push this limit? What am I
> > > > watching for and how do I watch for it? This
> > seems
> > > > like a very interesting area of study. I've
> > gotta do
> > > > a
> > > > dirt knap and then maybe google about or
> > something.
> > > > 
> > > > ron
> > > >  
> > > > > - Steve 
> > > > 
> > > > 
> > > > __________________________________
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> > > > 
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> > >
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