DSP Filters Demo updated, bugs fixed, latest tip


#1

DSP Filters has been updated to use an amalgamation formed from the latest modules branch:

UPDATED DSPFilters has moved to Github!


#2

Nice ! BTW I’ve been playing a little bit with your demo and it’s really nice. I’m really a DSP noob, so I was wondering where I could get basic information about the different kind of filters (RBJ biquad, Butterworth, Chebyshev, and so on …) and their characteristics . I imagine that if there are so many types available, it’s because they have all some advantages and disvantages right ?


#3

Changed the original post to note that DSP Filters has moved to Github.


#4

??


#5

I’m not sure I understand the question…I moved the project to Github, and updated it to use an amalgamated form of the latest modules tip…


#6

Haha, nah, the long version of my “??” question is “did you deliberately ignore my questions above or where you just too busy/bored/annoyed/tired ?”


#7

Oops, sorry! I didn’t know if it was serious or not…I mean, the Internet can provide much better answers than I can. But I will give it a shot.

“Butterworth” response is monotonically decreasing in the passband, “Chebyshev” response types have higher rolloffs, but there is ripple in the passband or stopband depending on the type. (as you can see in the graph). Elliptic response filters have ripple in both the passband and the stopband but in exchange you get the maximum possible rolloff.

Legendre response types are cool for two reasons. First, they have maximum rolloff while being monotonically decreasing (at the expense of some slope throughout the passband. But even cooler, DSP Filters is the only known existing digital implementation…the only information about using Legendre polynomials to build filters was in some electrical engineering book from the middle of the 20th century which is currently out of print.

These explanations are pretty rough, you’re a lot better off just reading about them on wikipedia (that’s what I do). I can’t honestly say I understand them completely (especially elliptics).