Finite Impulse Response (FIR) Sparse Filters

Collaboration diagram for Finite Impulse Response (FIR) Sparse Filters:

Functions
void	tpt_fir_sparse_f32 (f32_t *aOutData, tpt_fir_sparse_f32_t *aFilter, f32_t *aInData, f32_t *aBuf, uint32_t aCount)
	Processing function for the floating-point sparse FIR filter.
void	tpt_fir_sparse_init_f32 (tpt_fir_sparse_f32_t *aFilter, uint16_t aTaps, const f32_t *aCoeffs, f32_t *aState, int32_t *aTapDelay, uint16_t aMaxDelay, uint32_t aCount)
	Initialization function for the floating-point sparse FIR filter.
void	tpt_fir_sparse_init_q7 (tpt_fir_sparse_q7_t *aFilter, uint16_t aTaps, const q7_t *aCoeffs, q7_t *aState, int32_t *aTapDelay, uint16_t aMaxDelay, uint32_t aCount)
	Initialization function for the Q7 sparse FIR filter.
void	tpt_fir_sparse_init_q15 (tpt_fir_sparse_q15_t *aFilter, uint16_t aTaps, const q15_t *aCoeffs, q15_t *aState, int32_t *aTapDelay, uint16_t aMaxDelay, uint32_t aCount)
	Initialization function for the Q15 sparse FIR filter.
void	tpt_fir_sparse_init_q31 (tpt_fir_sparse_q31_t *aFilter, uint16_t aTaps, const q31_t *aCoeffs, q31_t *aState, int32_t *aTapDelay, uint16_t aMaxDelay, uint32_t aCount)
	Initialization function for the Q31 sparse FIR filter.
void	tpt_fir_sparse_q7 (q7_t *aOutData, tpt_fir_sparse_q7_t *aFilter, q7_t *aInData, q7_t *aBuf1, q31_t *aBuf2, uint32_t aCount)
	Function for the q7 Sparse FIR filter.
void	tpt_fir_sparse_q15 (q15_t *aOutData, tpt_fir_sparse_q15_t *aFilter, q15_t *aInData, q15_t *aBuf1, q31_t *aBuf2, uint32_t aCount)
	Function for the q15 Sparse FIR filter.
void	tpt_fir_sparse_q31 (q31_t *aOutData, tpt_fir_sparse_q31_t *aFilter, q31_t *aInData, q31_t *aBuf, uint32_t aCount)
	Processing function for the Q31 sparse FIR filter.

Detailed Description

Deprecated

Those functions are no more tested nor maintained and will be removed in a future version.

This group of functions implements sparse FIR filters. Sparse FIR filters are equivalent to standard FIR filters except that most of the coefficients are equal to zero. Sparse filters are used for simulating reflections in communications and audio applications.

There are separate functions for Q7, Q15, Q31, and floating-point data types. The functions operate on blocks of input and output data and each call to the function processes aCount samples through the filter. aInData and aOutData points to input and output arrays respectively containing aCount values.

Algorithm

The sparse filter instant structure contains an array of tap indices pTapDelay which specifies the locations of the non-zero coefficients. This is in addition to the coefficient array b. The implementation essentially skips the multiplications by zero and leads to an efficient realization.

     y[n] = b[0] * x[n-pTapDelay[0]] + b[1] * x[n-pTapDelay[1]] + b[2] *
     x[n-pTapDelay[2]] + ...+ b[numTaps-1] * x[n-pTapDelay[numTaps-1]]
 

Sparse FIR filter. b[n]

represents the filter coefficients" @par <code>pCoeffs</code> points to a coefficient array of aCount <code>numTaps</code>; <code>pTapDelay</code> points to an array of nonzero indices and is also of aCount <code>numTaps</code>; <code>pState</code> points to a state array of aCount <code>maxDelay + aCount</code>, where <code>maxDelay</code> is the largest offset value that is ever used in the <code>pTapDelay</code> array. Some of the processing functions also require temporary working buffers. @par Instance Structure The coefficients and state variables for a filter are stored together in an instance data structure. A separate instance structure must be defined for each filter. Coefficient and offset arrays may be shared among several instances while state variable arrays cannot be shared. There are separate instance structure declarations for each of the 4 supported data types. @par Initialization Functions There is also an associated initialization function for each data type. The initialization function performs the following operations: - Sets the values of the internal structure fields. - Zeros out the values in the state buffer. To do this manually without calling the init function, assign the follow subfields of the instance structure: numTaps, pCoeffs, pTapDelay, maxDelay, stateIndex, pState. Also set all of the values in pState to zero. @par Use of the initialization function is optional. However, if the initialization function is used, then the instance structure cannot be placed into a const data section. To place an instance structure into a const data section, the instance structure must be manually initialized. Set the values in the state buffer to zeros before static initialization. The code below statically initializes each of the 4 different data type filter instance structures <pre> tpt_fir_sparse_f32 aFilter = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay}; tpt_fir_sparse_q31 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay}; tpt_fir_sparse_q15 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay}; tpt_fir_sparse_q7 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay}; </pre> @par Fixed-Point Behavior Care must be taken when using the fixed-point versions of the sparse FIR filter functions. In particular, the overflow and saturation behavior of the accumulator used in each function must be considered. Refer to the function specific documentation below for usage guidelines. \ifile "/home/uranus/project/dsp/include/libdsp/tpt_math_filter.h"

Function Documentation

tpt_fir_sparse_f32()

void tpt_fir_sparse_f32	(	f32_t *	aOutData,
		tpt_fir_sparse_f32_t *	aFilter,
		f32_t *	aInData,
		f32_t *	aBuf,
		uint32_t	aCount )

Processing function for the floating-point sparse FIR filter.

Parameters

[out]	aOutData	points to the block of output data
[in]	aFilter	points to an instance of the floating-point sparse FIR structure
[in]	aInData	points to the block of input data
[in]	aBuf	points to a temporary buffer of aCount aCount
[in]	aCount	number of input samples to process

tpt_fir_sparse_init_f32()

void tpt_fir_sparse_init_f32	(	tpt_fir_sparse_f32_t *	aFilter,
		uint16_t	aTaps,
		const f32_t *	aCoeffs,
		f32_t *	aState,
		int32_t *	aTapDelay,
		uint16_t	aMaxDelay,
		uint32_t	aCount )

Initialization function for the floating-point sparse FIR filter.

Parameters

[in,out]	aFilter	points to an instance of the floating-point sparse FIR structure
[in]	aTaps	number of nonzero coefficients in the filter
[in]	aCoeffs	points to the array of filter coefficients
[in]	aState	points to the state buffer
[in]	aTapDelay	points to the array of offset times
[in]	aMaxDelay	maximum offset time supported
[in]	aCount	number of samples that will be processed per block

tpt_fir_sparse_init_q15()

void tpt_fir_sparse_init_q15	(	tpt_fir_sparse_q15_t *	aFilter,
		uint16_t	aTaps,
		const q15_t *	aCoeffs,
		q15_t *	aState,
		int32_t *	aTapDelay,
		uint16_t	aMaxDelay,
		uint32_t	aCount )

Initialization function for the Q15 sparse FIR filter.

Parameters

[in,out]	aFilter	points to an instance of the floating-point sparse FIR structure
[in]	aTaps	number of nonzero coefficients in the filter
[in]	aCoeffs	points to the array of filter coefficients
[in]	aState	points to the state buffer
[in]	aTapDelay	points to the array of offset times
[in]	aMaxDelay	maximum offset time supported
[in]	aCount	number of samples that will be processed per block

tpt_fir_sparse_init_q31()

void tpt_fir_sparse_init_q31	(	tpt_fir_sparse_q31_t *	aFilter,
		uint16_t	aTaps,
		const q31_t *	aCoeffs,
		q31_t *	aState,
		int32_t *	aTapDelay,
		uint16_t	aMaxDelay,
		uint32_t	aCount )

Initialization function for the Q31 sparse FIR filter.

Parameters

[in,out]	aFilter	points to an instance of the floating-point sparse FIR structure
[in]	aTaps	number of nonzero coefficients in the filter
[in]	aCoeffs	points to the array of filter coefficients
[in]	aState	points to the state buffer
[in]	aTapDelay	points to the array of offset times
[in]	aMaxDelay	maximum offset time supported
[in]	aCount	number of samples that will be processed per block

tpt_fir_sparse_init_q7()

void tpt_fir_sparse_init_q7	(	tpt_fir_sparse_q7_t *	aFilter,
		uint16_t	aTaps,
		const q7_t *	aCoeffs,
		q7_t *	aState,
		int32_t *	aTapDelay,
		uint16_t	aMaxDelay,
		uint32_t	aCount )

Initialization function for the Q7 sparse FIR filter.

Parameters

[in,out]	aFilter	points to an instance of the floating-point sparse FIR structure
[in]	aTaps	number of nonzero coefficients in the filter
[in]	aCoeffs	points to the array of filter coefficients
[in]	aState	points to the state buffer
[in]	aTapDelay	points to the array of offset times
[in]	aMaxDelay	maximum offset time supported
[in]	aCount	number of samples that will be processed per block

tpt_fir_sparse_q15()

void tpt_fir_sparse_q15	(	q15_t *	aOutData,
		tpt_fir_sparse_q15_t *	aFilter,
		q15_t *	aInData,
		q15_t *	aBuf1,
		q31_t *	aBuf2,
		uint32_t	aCount )

Function for the q15 Sparse FIR filter.

Parameters

[out]	aOutData	points to the output block data.
[in]	aFilter	points to an instance of the Sparse FIR structure.
[in]	aInData	points to the input block data.
[in]	aBuf1	points to a temporary buffer of length aCount.
[in]	aBuf2	points to a temporary buffer of length aCount.
[in]	aCount	number of the aCount.

tpt_fir_sparse_q31()

void tpt_fir_sparse_q31	(	q31_t *	aOutData,
		tpt_fir_sparse_q31_t *	aFilter,
		q31_t *	aInData,
		q31_t *	aBuf,
		uint32_t	aCount )

Processing function for the Q31 sparse FIR filter.

Parameters

[out]	aOutData	points to the block of output data
[in]	aFilter	points to an instance of the floating-point sparse FIR structure
[in]	aInData	points to the block of input data
[in]	aBuf	points to a temporary buffer of aCount aCount
[in]	aCount	number of input samples to process

tpt_fir_sparse_q7()

void tpt_fir_sparse_q7	(	q7_t *	aOutData,
		tpt_fir_sparse_q7_t *	aFilter,
		q7_t *	aInData,
		q7_t *	aBuf1,
		q31_t *	aBuf2,
		uint32_t	aCount )

Function for the q7 Sparse FIR filter.

Parameters

[out]	aOutData	points to the output block data.
[in]	aFilter	points to an instance of the Sparse FIR structure.
[in]	aInData	points to the input block data.
[in]	aBuf1	points to a temporary buffer of length aCount.
[in]	aBuf2	points to a temporary buffer of length aCount.
[in]	aCount	number of the aCount.