DSP_ifft16x16
[Fast Fourier Transform]

Collaboration diagram for DSP_ifft16x16:

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Detailed Description

void	DSP_ifft16x16 (const short *restrict ptr_w, int npoints, short *restrict ptr_x, short *restrict ptr_y)

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Function Documentation

void DSP_ifft16x16	(	const short *restrict	ptr_w,
		int	npoints,
		short *restrict	ptr_x,
		short *restrict	ptr_y
	)

This code performs a Radix-4 IFFT with digit reversal. The code uses a special ordering of twiddle factors and memory accesses to improve performance in the presence of cache. It operates largely in-place, but the final digit-reversed output is written out-of-place.

Parameters:

	ptr_w,:	Pointer to vector of Q.15 FFT coefficients of size 2*nx elements.
	npoints,:	Number of complex elements in vector x.
	ptr_x,:	Pointer to input vector of size 2*nx elements.
	ptr_y,:	Pointer to output vector of size 2*nx elements.

Algorithm:

DSP_ifft16x16_cn.c is the natural C equivalent of the optimized intrinsic C code without restrictions. Note that the intrinsic C code is optimized and restrictions may apply.

Assumptions:

In-place computation is not allowed.
Size of FFT, nx, must be power of 2 and 16<=nx<=32768.
The arrays for the complex input data x[], complex output data y[] and twiddle factor w[] must be double word aligned.
The input and output data are complex, with the real/imaginary components stored in adjacent locations in the array. The real components are stored at even array indices, and the imaginary components are stored at odd array indices.

Implementation Notes:

Endian Support: The intrinsic optimized C code supports both big and little endian modes.
The linear assembly code supports little endian mode only.
Interruptibility: The code is interruptible.

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Copyright 2014, Texas Instruments Incorporated