The AI Engine Dynamic Point FFT block in Vitis Model Composer allows taking FFT of different sizes (up to a maximum FFT size) of the input frame. The FFT size is determined by a header that is appended to every input frame. This example showcases the use of this block.

💡 Every input frame must be appended by a header.

💡 If the FFT size (N) is smaller than the frame size, the block takes the N point FFT of the first N samples in the input frame, and discards the rest of the samples in the frame.

💡 If the frame size is an integer multiple (M) of max FFT size, M FFT iterations will be performed on a given input frame, resulting in multiple iterations of output samples, reducing the number of times the kernel needs to be triggered to process a given number of input data samples. As a result, the overheads inferred during kernel triggering are reduced and overall performance is increased.

The picture below depicts the output of a Dynamic Point FFT block with a 128 point FFT, an input frame size of 2048 random inputs, and max fft size of 1024.

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