Dalhousie University
Faculty of Computer Science
CSCI 3162: Digital Media — Assignment 4
Winter Term 2021
due Tuesday, April 6, 23:59 ADT
1. Discrete Fourier Transform: Use the Fast Fourier Transform algorithm to compute the 8-point Discrete Fourier Transforms of sequences (1, 0, 1, 0, 1, 0, 1, 0) and (1, 1, 1, 1, 0, 0, 0, 0). Provide detailed
calculations with intermediate steps rather than just the results.
2. Audio analysis:
• Use MATLAB to analyze the first few seconds of piano.wav. Try to determine which notes
are played. Include the output of spectrogram and carefully explain your reasoning behind
the parameter settings that you have chosen. Annotate the plot if you can.
• Use MATLAB to generate the Discrete Fourier Transform of a pure sine wave, and those of the
same sine wave quantized using a bit depth of six and a dithered version of the latter. Plot all
three magnitude spectra (paying attention to the correct scaling and labelling of the axes) and
discuss the differences. From the spectra, can you infer why the dithered version sounds less
objectionable than the undithered one? Marks will be based on the interpretability of the plots
as well as on the correctness and significance of the conclusions.
3. Deconvolution:
• Generate a blurred, noisy version of the cameraman image as described on the lecture slides.
• Write MATLAB code that implements the Wiener filter for deconvolution. Do not use MATLAB’s
deconvwnr. • Use the code that you have written the deblur the image, first with the (sharp) cameraman power
spectrum, then with that of the building. In each case, compute the sum of squared errors that
the Wiener filter strives to minimize.
Submission instructions: Please submit your solutions on Brightspace. Remember that
• All work you submit must be your own.
• Any questions you may have should be brought up during class time or posted on the Brightspace
discussion board.
• You must not share your calculations or code with anyone.
• You must not make use of any code you find on the web.