Unless you consider the papers by Mitra et alias, but dealing only with linear 
graphs computability…which are dated effectively in the 70s.

 

M.

 

Da: music-dsp [mailto:music-dsp-boun...@music.columbia.edu] Per conto di Marco 
Lo Monaco
Inviato: sabato 25 luglio 2015 01:31
A: music-dsp@music.columbia.edu
Oggetto: [music-dsp] R: Re: The Art of VA Filter Design book revision 1.1.0

 

Ciao Vadim,

On page viii the name of my dear friend and coworker Federico Avanzini is the 
correct one.

 

Also you tell us that the delay free loop problem was initially faced in the 
70s, which is something I didn't know. Do you have please any citation about it?

 

Cheers

 

Marco

 

 

Inviato dal mio dispositivo Samsung



-------- Messaggio originale --------
Da: robert bristow-johnson <r...@audioimagination.com> 
Data: 24/07/2015 12:48 (GMT-08:00) 
A: music-dsp@music.columbia.edu 
Oggetto: Re: [music-dsp] The Art of VA Filter Design book revision 1.1.0 


hey Vadim,

i love the rigor in your paper.  i'm still looking through it.

in the 2nd-order analog filters, i might suggest replacing "2R" with 1/Q 
in all of your equations, text, and figures because Q is a notation and 
parameter much more commonly used and referred to in either the EE or 
audio/music-dsp contexts.

in section 3.2, i would replace n0-1 with n0 (which means replacing n0 
with n0+1 in the bottom limit of the summation).  let t0 correspond 
directly with n0.

now even though it is ostensibly obvious on page 40, somewhere (and 
maybe i just missed it) you should be explicit in identifying the 
"trapezoidal integrator" with the "BLT integrator".  you intimate that 
such is the case, but i can't see where you say so directly.

section 3.9 is about pre-warping the cutoff frequency, which is of 
course oft treated in textbooks regarding the BLT.  it turns out that 
any *single* frequency (for each degree of freedom or "knob") can be 
prewarped, not only or specifically the cutoff.  in 2nd-order system, 
you have two independent degrees of freedom that can, in a BPF, be 
expressed as two frequencies (both left and right bandedges).  you might 
want to consider pre-warping both, or alternatively, pre-warping the 
bandwidth defined by both bandedges.

lastly, i know this was a little bit of a sore point before (i can't 
remember if it was you also that was involved with the little tiff i had 
with Andrew Simper), but as depicted on Fig. 3-18, any purported 
"zero-delay" feedback using this trapezoidal or BLT integrator does get 
"resolved" (as you put it) into a form where there truly is no 
zero-delay feedback.  a "resolved" zero-delay feedback really isn't a 
zero-delay feedback at all.  the paths that actually feedback come from 
the output end of a delay element.  the structure in Fig 3-18 can be 
transposed into a simple 1st-order direct form that would be clear *not* 
having zero-delay feedback (but there is some zero-delay feedforward, 
which has never been a problem).

i'll be looking this over more closely, but these are my first 
impressions.  i hope you don't mind the review (that was not explicitly 
asked for).

L8r,

r b-j


On 7/24/15 6:58 AM, Vadim Zavalishin wrote:
> Released the promised bugfix
> http://www.native-instruments.com/fileadmin/ni_media/downloads/pdf/VAFilterDesign_1.1.1.pdf
>  
>
>
> On 22-Jun-15 10:51, Vadim Zavalishin wrote:
>> Didn't realize I was answering a personal rather than a list email, so
>> I'm forwarding here the piece of information which was supposed to go to
>> the list:
>>
>> While we are on the topic of the book, I have to mention that I found
>> the bug in the Hilbert transformer cutoff formulas 7.42 and 7.43. Tried
>> to merge odd and even orders into a more simple formula and introduced
>> several mistakes. The necessary corrections are (if I didn't do another
>> mistake again ;) )
>> - the sign in front of each occurence of sn must be flipped
>> - x=(4n+2+(-1)^N)*K(k)/N
>> - the stable poles are given by n<N/2 for N even and n<(N+1)/2 for N 
>> odd.
>>
>> I plan to release a bugfix update, but want to wait for possibly more
>> bugs being discovered.
>>
>> Regards,
>> Vadim
>>
>>
>


-- 

r b-j                  r...@audioimagination.com

"Imagination is more important than knowledge."



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