- Audio project
- FFT Video
- FFT Video 2048
Simple variation of the base block design of PYNQ Z2 board. It will simply stream the audio through Vivado IPs I2S Rx-Tx (AXI stream @ 100 MHz); PYNQ audio codec will take care of the analog-to-digital and digital-to-analog conversions.
AXI audio stream demuxed in L-channel and R-channel, 1024-point FFT (Vivado IP) is applied to both channels and finally the output magnitude is displayed on an HDMI monitor (1920x1080 @ 30Hz).
Same as the previous version with some tweaks. Only a real input is fed into the FFT and, as suggested in the vivado FFT logic core documentation, only the second half of the output is considered.
A windowing is added to lowering spectral leakage, by default no window is applied; to enable windowing it is necessary to set the selector to '1', it will multiply the input by a factor stored in a dual port RAM accessible from the notebook.
In the BRAM is initially stored an Hann-function, but is also selectable Hamming, Cosine, Gaussian and Rectangular windows or it is possible to define a custom function (via Python notebook).
It is possible to dispaly the log2 of the output. The logarithm is computed using a priority encoder and a III order taylor expasion.
FFT xilinx IP parameters:
- 2048 N-point
- Scaled (fixed point)
- 24 bit input/output width
- Pipelined/Streaming architecture
- Non real time
- Index is embedded in the TUSER axis output
- Video frame overlay to show the frequency axis (in the display)
- Sync FFT output ($$\sim23$$Hz) with the monitor refresh rate (30Hz)
- Find a better way to display the spectrum (now is linear in the frequencies)
This is an example of the logarithm result.
Actual FFT output of an input song.
