Quote:
Originally Posted by Russ
I think that you will find that most of the more complicated filters used in existing kX plugins are IIR filters because they require less resources to implement.
Feedback here means a recursive filter (filters use previous outputs and/or inputs).
|
Ok - I think I get it. (Max's Explanation of 'delay' and feedback' - seems like a reasonable interpretation to me - Thanks to both of ya)
Tho - it seems more like plain old 'delay' - than 'delay+feedback' to me...
DSP GURUS use of 'feedback' must be more derived from 'feedback' from resonant active analog filters.. (doh!- that makes more sense too)
Quote:
Originally Posted by Russ
i.e.
If you look at the difference equation for the filter, you might see something like the following:
y[n] = b0*x[n] + b1*x[n-1] + b2*x[n-2] - a1*y[n-1] - a2*y[n-2]
In the above:
y[n] is the output of the filter
y[n-1] is the previous output of the filter
y[n-2] is the output from 2 cycles ago
x[n] is the current input (current sample)
x[n-1] is the previous input
x[n-2] is the input from 2 cycles ago
You wouldn't really use Tram to implement the delays here, rather you would just use static registers.
i.e. (code implementation would do the following)
y = b0*x + b1*x1 + b2*x2 - a1*y1 - a2*y2
y2 = y1
y1 = y
x2 = x1
x1 = x
The above is used for most of the EQ plugins bundled with kX.
|
Ok - I didn't realize they were using statics to achieve delays of > 1 sample. I thought I seen one use iTram - but I could be mistaken - Ive been looking at alot of DANE...so... ??
Quote:
|
BTW: I should also add that your typical echo delay using Tram would also be an IIR filter, but I was trying to make the point that Tram is not necessary (i.e. if you a trying to use Tram as the identifier).
|
Ok I got ya... (*forgot most any DSP algo can be referred to as a 'filter as well - but my previous use of 'filter' was aimed at what you assumed correctly - LP/BP/HP)
Is there a FIR filter example (in DANE) in existence? - so I can get a better understanding of just how much resources are needed - looking at the formulas - it would look like ~ 3x amount of instructions (guessing) - but wonder what the audible difference there would be as well - seeing as I read IIR are 'less accurate' and 'prone to errors'.
My experiments have seemed to be 'noisy' and wonder if this noise was from 'errors' I read about. ??
Thanks guys.
Mark