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Explaining how this filter is working

Started by wijesijp June 28, 2010
I am building a simple equalizer type audio application and I found
following filter online

http://musicdsp.org/files/CFxRbjFilter.h

The application is working but now I need to modify this filter. I am new
to DSP and I have a hard time figuring it out. 

Can anyone explain how this filter is working? 

On 28/06/2010 16:31, wijesijp wrote:
> I am building a simple equalizer type audio application and I found > following filter online >
NB it is actually a whole set of filters; you pick and choose the type you want to use (bandpass, low shelf, etc).
> http://musicdsp.org/files/CFxRbjFilter.h > > The application is working but now I need to modify this filter.
To do what? I am new
> to DSP and I have a hard time figuring it out. >
It's not a good idea to modify dsp code unless you ~really~ know what you are doing. Any introductory text on dsp and digital filters will get you started, but it is not something that can be learned quickly from scratch. If you just want to change the C++ class design keeping the dsp unchanged that is a separate question, not really on topic here. IMO that code does not really leverage C++ as it might (not at all well suited to efficient real-time use with dynamically varying parameters); there is plenty of scope for a different approach more suited to a real-time interactive application such as a plugin.
> Can anyone explain how this filter is working? >
The author already has done - look for the files on the same site linked by "RBJ Audio-EQ-Cookbook". Richard Dobson

Richard Dobson wrote:

> > It's not a good idea to modify dsp code unless you ~really~ know what > you are doing.
Sticking together some googled pieces of code without any clue about what they doing is the essence of modern programming. Things are changing so fast that there is no point in learning anything in details. There is no documentation and no reason for documenting anything, as all of that will be outdated in 2-3 years.
> Any introductory text on dsp and digital filters will get > you started, but it is not something that can be learned quickly from > scratch.
This is grandpa's method. It is old fashioned, non-productive and boring :-) VLV

wijesijp wrote:

> I am building a simple equalizer type audio application and I found > following filter online > > http://musicdsp.org/files/CFxRbjFilter.h > > The application is working but now I need to modify this filter. I am new > to DSP and I have a hard time figuring it out. > > Can anyone explain how this filter is working?
How about I do the work and you paying me for that? Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
On 06/28/2010 12:13 PM, Vladimir Vassilevsky wrote:
> > > Richard Dobson wrote: > >> >> It's not a good idea to modify dsp code unless you ~really~ know what >> you are doing. > > Sticking together some googled pieces of code without any clue about > what they doing is the essence of modern programming. Things are > changing so fast that there is no point in learning anything in details. > There is no documentation and no reason for documenting anything, as all > of that will be outdated in 2-3 years. > >> Any introductory text on dsp and digital filters will get you started, >> but it is not something that can be learned quickly from scratch. > > This is grandpa's method. It is old fashioned, non-productive and boring > :-)
Trying to drum up business a few months in the future? You know it's better to get it early, when they're not in a hurry, rather than late. Even if they are so desperate that they don't quibble about the cost, those 12-hour days are still a pain in the behind. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html
On Jun 28, 3:13&#2013266080;pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
> > This is grandpa's method. It is old fashioned, non-productive and boring :-) >
i'll have you know, Sonny, that while i am in the generation of grandpa's (i'm a great uncle, a *really* great uncle), i ain't no grampa yet. my kids are still under 14. i might get a little upset if i became a grampa in the near future. r b-j