pls ignore this thing, its for college minor project documentation

1

Got FFT to work

time windowing function

10*sin(TWOPI*i/(0.4*WINDOW)) + 5*sin(TWOPI*i/(0.05*WINDOW)) + 2*sin(TWOPI*i/(0.1*WINDOW))

EQ is an 8 point Freq gain control

d_vec EQ_SETTINGS = {1.4,5.0,0.2,2.0,3.0,1.0,1.0,3.0,5.0};

this is being interpolated by using Cubic interpolation scheme Interpolate(EQ_SETTINGS,32) and is convoluted to the frequency response

eq_filtered = convolve(freqDomain,EQ_INTERPOLATED);

Windowing ( Blackman ) Window is considered.

2

Fixed a bug where filter was not being applied properly to negative frequencies leading to weird filtering issues

LOW PASS FILTER

LEFT The filter is not being flipped RIGHT Is how the filter must be applied

AUDACITY Freq plot

3

Decided to use ffmpeg due to it being faster and more efficient than mess of for loops i wrote ;-; made a basic ffmpeg wrapper /include/ffmpeg_wrapper.h from ffmpeg documentation, implemented bare stuff which are required to perform what project needs to do.

source.addFilter( frequency_in_Hz , gain_in_db );

ffmpeg documentation firequalizer=gain_entry='entry(100,0);'

realtime audio playback

ffmpeg -i song.wav -f wav pipe:1 | ffplay -i - allows to pipe ffmpeg output realtime to ffplay

4

Raspberry pi zero (which is being used in the presentation of project) doesn't have the required DAC to generate audio output so we pipe output through the PWM pins of rpi0.