I've succeeded to compute complex FFT of a data array of interleaved values using the arm_cfft_f32() API of the CMSIS DSP library for Cortex-M4, and got in the same array the FFT results as frequency domain values with the same interleaving.

I chose a result value of the Frequency Domain (let say a point) based on a specific criteria, and want to go back to the initial index (in the Time Domain) before calculating the FFT and passing through arm_cfft_radix8by4_f32() API.

Is there anyway to go in the opposite sens, and identify a point based on its FFT result value ?

Thanks and regards, tinymanta.


I think you're misunderstanding the relationship between the time and frequency domains. Each point in the output of a DFT is a function of all of the input time-domain values. There is no one-to-one mapping between input points and output points.


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