[ardour-users] TAP Dynamics question - not directly ardour related

Tom Szilagyi st444 at hszk.bme.hu
Fri Jun 18 13:50:01 PDT 2004

On Fri, Jun 18, 2004 at 10:26:06AM -0500, Josh Karnes wrote:
> Working on developing some new functions for TAP Dynamics to do optical 
> compression emulation, [...]

That would be really great :)

> 1.  is the "offset gain" control really a threshold control in disguise?  I 
> mean, does it have pretty much exactly the same effect as threshold?

No, and yes. The offset gain is generally not a threshold
level. Quoting from the documentation (skip it if you know it

  By setting this control, you specify the gain with which the whole
  dynamics function is shifted horizontally, in the negative
  direction. To put it another way, you may think of this control like a
  gain control applied to the input signal just before it reaches the
  envelope stage [...] Use this control to adjust the chosen function
  to the actual level of your track.

But if it is a limiter or a compressor function, the effect is
actually very much the same as if it were a threshold control. But the
whole point is that one can define arbitrary transfer functions, so
the term 'threshold' does not necessarily make any sense. At least
that's the way I think of it.

> 1a.  If the answer to #1 is "yes", then would it make sense to call it 
> "threshold", make the default (0.000 position) "-6dB", and then just make 
> every "function" definition run at -6dB, thus eliminating "threshold" from 
> the function def's?  This way "function" control would just select ratio, 
> type of dynamics effect, and not threshold (since it's externally 
> controllable)

I would not rename 'offset gain' to 'threshold', because that's not
what it is to my understanding (although the effect of it is similar
given a certain subset of dynamics functions, as explained above). Of
course if you make a new plugin based on mine, you call it whatever
you want. In particular, if you intend to have only compressor/limiter
functions, it is perfectly admittable to do it the way you explained.

> 2.  What is the max for NUM_MODES ?

There is no artificially imposed limit for that.

> Also, while I'm at it, does adding points to the curve add to the processor
> load, latency, etc. of the plugin?

This only causes the get_table_gain() function to have a little more
work. I have no benchmarks for that in particular, but I wouldn't
think it's a big deal.

> You can email me directly if you would like to discuss, but I tried the 
> sourceforge address and also the address you use on the ardour list and 
> they both bounce.

If it really doesn't work, try sending to tszilagyi at index.hu

> As you can probably tell, I am considering building a 
> new compressor plugin based on yours.

Have a lot of fun with it. :)
And if you have any usable functions, please send them so my plugin
may as well evolve.


ps. get ready for a _big_ tap-plugins release in 1 week! :)

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