DSP_fir_sym
[Filtering and convolution]

Collaboration diagram for DSP_fir_sym:

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Detailed Description

void	DSP_fir_sym (const short *restrict x, const short *restrict h, short *restrict r, int nh, int nr, int s)

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Function Documentation

void DSP_fir_sym	(	const short *restrict	x,
		const short *restrict	h,
		short *restrict	r,
		int	nh,
		int	nr,
		int	s
	)

This function applies a symmetric filter to the input samples. The filter tap array h[] provides ‘nh+1’ total filter taps. The filter tap at h[nh] forms the center point of the filter. The taps at h[nh - 1] through h[0] form a symmetric filter about this central tap. The effective filter length is thus 2*nh+1 taps. The filter is performed on 16-bit data with 16-bit coefficients, accumulating intermediate results to 40-bit precision. The accumulator is rounded and truncated according to the value provided in ‘s’. This allows a variety of Q-points to be used.

Parameters:

	x	= Input array [nr+2*nh elements]
	h	= Coeff array [nh+1 elements]
	r	= Output array [nr elements]
	nh	= Number of coefficients
	nr	= Number of output samples
	s	= Number of insignificant digits to truncate e.g., 15 for Q.15 input data and coefficients

Algorithm:

DSP_fir_sym_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:

Arrays x, h, and r do not overlap.
x, h and r must be double word aligned.
nr >= 4; nr % 4 == 0.
nh >= 4; nh % 4 == 0.

Implementation Notes:

Endian Support: The code supports both big and little endian modes. Interruptibility: The code is interruptible

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Copyright 2014, Texas Instruments Incorporated