pfft~ access to single bin


    Sep 26 2011 | 2:01 pm
    Hey!
    I look around in max's help files but I can't find answer form my question.
    Do you know how to get access to single bin in fft frame in real time?
    Is it possible with max?
    Tahanks,
    wo

    • Sep 26 2011 | 2:37 pm
      The rightmost outlet of fftin~ gives you the bin index.
    • Sep 29 2011 | 9:30 am
      Ok :)
      But how can I get access to this data? With snapshot~ or buffer~ ?
      Let say I want make a simple spectrogram based on fft~ with pfft~ and multislider. What should I put in the middle?
      Thanks for help!
    • Sep 29 2011 | 4:03 pm
      It depends where you want to store you data. If you want to make a spectrogram, I suggest you to store FFT data in a matrix (jit.matrix) using jit.peek~ to store and jit.poke~ to read the data. Working with FFT data is sooo much easier and more intuitive when the data is stored in a matrix that I really suggest you to go in that direction.
      J.F. Charles published an awesome article in Computer Music Journal back in 2008 called A Tutorial on Spectral Processing Using Max/MSP and Jitter. There are also many accompanying patches to that article...have a search on the web. Priceless source of information!
      PS: And you will have to decide between using fft~ or pfft~. There is no point in using both. At least not for what you want to do.
      PS2: In case you're not familiar with Jitter, you really need to know just few basics in order to create Spectrogram, so...I would say Jitter is the way forward:)
    • Sep 29 2011 | 4:04 pm
      PS: I am just writing my dissertation on that topic, it will be finished very soon. Detailed description of spectral processing in Max/Jitter...stay tuned, 160 pages already:)
    • Sep 29 2011 | 6:19 pm
      Thanks a million for the great answer!
      I will be happy if let me know when you finalize your article.
      :)
    • Sep 30 2011 | 4:28 am
      If you really want to isolate just a single bin (as opposed to displaying the entire spectrum), this may not be the most efficient way imaginable, but it works. (The example uses fft~ instead of fftin~, but the principle is the same.)
    • Jan 19 2012 | 9:29 am
      @ t: Did you finish your dissertation? I'd love to read it.
      Cheers, A
    • Jan 20 2012 | 10:09 pm
      Thanks for the tips t! I'd love to peek at some of your dissertation as well. This is something I've been contemplating pursuing as well!
      Jeff
    • Jan 20 2012 | 11:53 pm
      You can use ==~ and sah~ to accomplish this. (as in when the bin# is equal to n, sample the value and continue holding it until the next frame. You can use send~ on this. You may need to divide by the number of overlap since you're adding multiple values together)