A proper "Limiter" effect

[steve]

"Hard Limiter" is a wave-shaping effect not a real "limiter".
All it actually does is to apply "clipping", scale the chopped of peaks a bit smaller and stick them back on.

"Leveller" is no substitute for a limiter.

"Compressor" does not have a limiter.

Because of this I find myself often recommending to users requiring a limiter that they install the "Brick Wall Limiter" from here: http://forum.audacityteam.org/viewtopic ... 98#p150498

The Brick Wall Limiter is a simple effect and will generally produce much better results than are possible with the standard Audacity tools.
The effect is GPL v2 and I'd be happy for it to be used as is, or with minor interface modifications, or recoded in C/C++ as a built-in effect.

As a simple demonstration, here is a comparison to show the harmonic distortion when limiting a high amplitude 1 kHz sine wave, (It should be a single horizontal line if there is no distortion):

tracks002.png (28.21 KiB) Viewed 8076 times

[Gale Andrews]

Because of this I find myself often recommending to users requiring a limiter that they install the "Brick Wall Limiter" from here: http://forum.audacityteam.org/viewtopic ... 98#p150498

The download link was broken but I updated it (I assume you removed the faulty version but did not replace the link in the first post).

So for which purpose does the user choose each of these instead of the "Brickwall":
Standard Limiter
Broadcast Limiter


Gale

[steve]

The difference between "standard limiter" and "brick wall limiter" is like the difference between soft knee and hard knee compression (respectively).

The "standard" limiter will probably sound more "transparent" when a small amount of limiting is required. I would probably choose this if I wanted to get just a little more volume on a classical music recording if there were a few peaks preventing further amplification.

If the aim is "just make it louder", then the brick wall limiter is the one to use.

Broadcast Limiter is a wave shaping effect, similar to the LADSPA "Hard Limiter" but more refined.
This is currently up to version IV (on the forum). Version IV is a little more refined again ("smoother" compression of the peaks) but is not on the wiki yet because there is a bug in it that needs fixing. This would be good for radio communications where maximising the signal is more important than a bit of distortion.

There is also "Soft Clipping Limiter" which is similar to Broadcast Limiter but less extreme and is better suited to music applications than Broadcast Limiter because the distortion is much less.

[Gale Andrews]

If you want to replace the LADSPA Hard Limiter with another shipped limiter, then perhaps you want to consider to what extent the current "Limiters" on offer can be combined.

As you know I find "Hard Limiter" useful at times for audio restoration and it has some value (used in moderation) as a crude, "simple" way of reducing dynamic range.

"Brickwall Limiter" is obviously "simple" enough to appeal to users who struggle with Compressor. Is it possible to combine it with something like your "Limiter" for more subtle usage?

Can one "waveshaping" limiter be produced? I don't see it being shipped in Audacity, though.


Gale

[steve]

Yes I think we could have one limiter effect with:

Limiter (type): [Brick Wall | Soft Knee | Clipping (Hard) | Clipping (Soft) | Clipping (Softest)]
Input Gain (dB): <--|-->
Limit to (dB): <--|-->

[steve]

Better still:

Limiter (type):

Code: Select all

Brick Wall
Soft Knee
Crusher (light)
Crusher (Medium)
Crusher (Heavy)
Crusher (Heaviest)
Clipping (Hard)
Clipping (Medium)
Clipping (Soft)
Clipping (Softest)

Input Gain (dB): <--|-->
Limit to (dB): <--|-->

Where "Crusher" emulates the "Leveller" effect.

[Gale Andrews]

Better still:

Limiter (type):

Code: Select all

Brick Wall
Soft Knee
Crusher (light)
Crusher (Medium)
Crusher (Heavy)
Crusher (Heaviest)
Clipping (Hard)
Clipping (Medium)
Clipping (Soft)
Clipping (Softest)

Input Gain (dB): <--|-->
Limit to (dB): <--|-->

Where "Crusher" emulates the "Leveller" effect.

So "Crusher" and "Clipping" are WaveShapers?

Should Limiters-cum-WaveShapers have any useful parameters not needed in a "simple" limiter, such as an Exciter, that makes it better to give them their own plug-in?



Gale

[steve]

Should Limiters-cum-WaveShapers have any useful parameters not needed in a "simple" limiter, such as an Exciter, that makes it better to give them their own plug-in?

A fairly "full featured" hardware limiter would probably have:

• Input gain
• lookahead
• hold
• release
• output gain

Though it could have more controls including "slew rate" or "Attack / Recovery", "Side Chain Filter", "Stereo Link".
A digital effect may also have "emulation modes" that emulate the characteristics of analogue limiters.

Limiters are frequently combined with compressors so that one unit is used for dynamic processing (sometimes called a "compressor/limiter").
One of the few companies to manufacture dedicated limiters for studio work is Chandler. This is one of their more complicated units: http://www.chandlerlimited.com/products ... imiter.php

At the other extreme a limiter could have just one user control for "limit to dB".
On some compressors the limiter control can be a simple on/off button.

[waxcylinder]

Steve do you want me to xfr this to Wiki>PFR or would you prefer to write a proposal (keeping this thread acrchived) ?

Peter

[steve]

Please transfer the initial request (A proper "Limiter" effect) to Wiki>PFR and then archive the topic so that I can use it in a proposal (in due course).