FFT Example: Unraveling the Recursion

81,299
25
Published 2020-11-15
This video is meant as further support to the main video on the FFT    • The Fast Fourier Transform (FFT): Mos...  
We break down how the FFT evaluates a particular polynomial at the roots of unity by unraveling the recursive process completely.

0:00 Introduction
1:13 FFT Example Breakdown

Support: www.patreon.com/reducible

This video wouldn't be possible without the open source manim library created by 3blue1brown: github.com/3b1b/manim

Here is link to the repository that contains the code used to generate the animations in this video: github.com/nipunramk/Reducible

Music:
All music by Aakash Gandhi

All Comments (21)
  • @kiranraaj7889
    Why doesnt this channel have the recommendation it deserves. Its by far the best CS edutainment channel I have discovered yet.
  • @user-bq7uk4lr8e
    Finally I have found an explanation that makes sense. Many thanks!
  • I remember studying the FFT in college (some 50 years ago) and I used it throughout my career. I’m now retired, but I still love to watch videos on Maths. Yours are particularly clear; in fact, they are works of art. Excellent!
  • @NTNscrub
    This series alone earned you my subscription. It ain't much, but it's something. Thank you for the explanations.
  • @vi5hnupradeep
    Thankyou so much for this very intuitive breakdown of fft ! Commenting so that ,this series will get the views it deserves.
  • @mubashirsoomro6
    What a lovely set of videos! it helped me refresh my memories from Signal Processing classes. Would have loved to see some butterfly diagrams though, they are very beautiful to look at and quite useful to visually understand the process.
  • @berkealgul2503
    Man... learning computer science with 3b1b style. Insta sub
  • @Zmunk19
    thanks for this example, I wouldn't have understood the FFT without it
  • @jackblack4246
    I love your channel! I run my high school computer club and your videos are an invaluable resource for both learning and teaching!
  • @Flash-qr5oh
    Please continue making these videos they are so helpful
  • you always make me cry, be its tower of hanoi, recursion in number of colour, now fast fourier. Thanks a lot for being so supportive
  • @GhenGhost
    I have been mulling over the FFT for WEEKS. Finally I have understood it, just by seeing that for 4 elements, the number of multiplications we did was 2*2+4 = 8 = 4 log2(4), compared to 4^2 = 16 for the DFT. For 8, it would be 4*2+2*4+8 = 24 = 8log2(8), compared to 8^2 = 16. I have an exam on this this Monday, so thanks to you if i ace the FFT question!
  • @nicknichols4879
    Why does this channel only have 20k subscribers?? Great content.
  • i remember how i fought my way through this algorithm :D very good video!
  • @fhz3062
    I'd like to add a very interesting point. While working with discrete signals, it common to use Z- transform. It leads a vector to a polynom in the variable z. The interesting point is that a polynomial multiplication is the convolution of its coefficients. The discrete convolution can be performed with a "smart" internal product. "Smart" because of size of results, where the product starts and finishes for each and a back to front flip. I'd be glad with a Z transform video. :)