adjust downsample rate fft size
Revert 14126fe..a9a5f44

This rolls back to commit 14126fe9e6b9290b6e3c9689027af8a2dcb0ca63.
backup
Revert a9a5f44..762cf7f

This rolls back to commit a9a5f44fbab51c52405f03ad400fdecb2095a435.
FFT bug fixed