Audacity Forum

Update -- I fixed one stupid bug where I computed 2/x when I wanted x/2. So here's a little screenful of code. As explained I want to attach labels to the "hot spots" at a certain frequency. It's doing something approximately like that. I don't yet know the intelligent things to do with the window s...

I hadn't heard about the number 1020.

Should snd-fft be given only window sizes of 2^n samples?

So the first coefficient is dc offset, then there are pairs of coefficients for multiplies of sample rate / window. I got that.

sqrt (a * a + b * b) is not the rms of a and b, but sqrt(2) times that, duh I misspoke. Are we talking about the same code? I thought you meant Steve's fft-modulator-class example on this page. http://www.audacity-forum.de/download/edgar/nyquist/nyquist-doc/examples/rbd/03-fft-tutorial.htm Samples f...

No, that doesn't answer my question. That shows how you combine corresponding entries of two corresponding frames. Scale the coefficients of one by the rms's of pairs of coefficients of the other. That doesn't tell me how I compare coefficients with a scalar dB value. The simple exercise I'm trying,...

Okay! I wrote and debugged some simple code (maddening, make stupid errors and Nyquist just chokes with no clue, but anyway). I've got something that iterates over frames. But, now what? How do I interpret the numbers in the frames? What are their units? If I make a control for my analyzer with a -d...

To clarify, the questions, about how snd-inverse is implemented under the hood, are these: (1) if you call snd-inverse repeatedly on the same sound, are the later calls constant-time, because the first call precomputes and remembers an inverse lookup for the whole sound? Or, (2) does snd-inverse res...

Okay, let me see if I'm getting this. The page I first linked to says: "Instead, Nyquist violates its "pure" functional model and resorts to objects for FFT processing. A sequence of frames is represented by an XLISP object. Whenever you send the selector :next to the object, you get back either NIL...

Original discussion here http://forum.audacityteam.org/viewtopic ... ng#p191079

Robert J H referred me to this piece of code for finding zero crossings efficiently. I think I get what it's doing, but I don't understand some things. What is the unused variable "zero" for? Is the loop calling sref-inverse really efficient (the builtin function doing some one time caching) or it t...

I will likely put the tricks for finding zero crossings that others have suggested, in there.