This routine implements the DIF (decimation in frequency) complex radix 4 FFT with digit-reversed output and normal order input. The number of points, ‘n’, must be a power of 4 {4, 16, 64, 256, 1024, ...}. This routine is an in-place routine in the sense that the output is written over the input. It is not an in-place routine in the sense that the input is in normal order and the output is in digit-reversed order. There must be n complex points (2*n values), and 3*n/4 complex coefficients (3*n/2 values).
@param x Pointer to an array holding the input and output floating-point array which contains ‘n’ complex points.
@param w Pointer to an array holding the coefficient floating-point array which contains 3*n/4 complex numbers.
@param n Number of complex points in x.
- Algorithm:
- DSPF_sp_cfftr4_dif_cn.c is the natural C equivalent of the optimized linear assembly code without restrictions. Note that the linear assembly code is optimized and restrictions may apply.
- Assumptions:
- N needs to be power of 4
- Implementation Notes:
- Interruptibility: The code is interrupt-tolerant but not interruptible.
Endian Support: The code supports both big and little endian modes.