    (padding factor for the FFT) - optional (can take values -1,0,1,2...).</span>
0035 <span class="comment">%                    -1 corresponds to no padding, 0 corresponds to padding</span>
0036 <span class="comment">%                    to the next highest power of 2 etc.</span>
0037 <span class="comment">%                       e.g. For N = 500, if PAD = -1, we do not pad; if PAD = 0, we pad the FFT</span>
0038 <span class="comment">%                       to 512 points, if pad=1, we pad to 1024 poi