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/* nfilterkit.h -- header for adapted version of filterkit */
typedef char BOOL;
typedef short HWORD;
typedef unsigned short UHWORD;
typedef int WORD;
typedef unsigned int UWORD;
#define MAX_HWORD (32767)
#define MIN_HWORD (-32768)
#ifdef DEBUG
#define INLINE
#else DEBUG
/* #define INLINE inline */
#define INLINE
#endif DEBUG
/*
* FilterUp() - Applies a filter to a given sample when up-converting.
* FilterUD() - Applies a filter to a given sample when up- or down-
*/
/* Conversion constants */
#define Nhc 8
#define Np (Nhc+Na)
/* Description of constants:
*
* Npc - is the number of look-up values available for the lowpass filter
* between the beginning of its impulse response and the "cutoff time"
* of the filter. The cutoff time is defined as the reciprocal of the
* lowpass-filter cut off frequence in Hz. For example, if the
* lowpass filter were a sinc function, Npc would be the index of the
* impulse-response lookup-table corresponding to the first zero-
* crossing of the sinc function. (The inverse first zero-crossing
* time of a sinc function equals its nominal cutoff frequency in Hz.)
* Npc must be a power of 2 due to the details of the current
* implementation. The default value of 512 is sufficiently high that
* using linear interpolation to fill in between the table entries
* gives approximately 16-bit accuracy in filter coefficients.
*
* Nhc - is log base 2 of Npc.
*
* Na - is the number of bits devoted to linear interpolation of the
* filter coefficients.
*
* Np - is Na + Nhc, the number of bits to the right of the binary point
* in the integer "time" variable. To the left of the point, it indexes
* the input array (X), and to the right, it is interpreted as a number
* between 0 and 1 sample of the input X. Np must be less than 16 in
* this implementation.
*
* Nh - is the number of bits in the filter coefficients. The sum of Nh and
* the number of bits in the input data (typically 16) cannot exceed 32.
* Thus Nh should be 16. The largest filter coefficient should nearly
* fill 16 bits (32767).
*
* Nb - is the number of bits in the input data. The sum of Nb and Nh cannot
* exceed 32.
*
* Nhxn - is the number of bits to right shift after multiplying each input
* sample times a filter coefficient. It can be as great as Nh and as
* small as 0. Nhxn = Nh-2 gives 2 guard bits in the multiply-add
* accumulation. If Nhxn=0, the accumulation will soon overflow 32 bits.
*
* Nhg - is the number of guard bits in mpy-add accumulation (equal to Nh-Nhxn)
*
* NLpScl - is the number of bits allocated to the unity-gain normalization
* factor. The output of the lowpass filter is multiplied by LpScl and
* then right-shifted NLpScl bits. To avoid overflow, we must have
* Nb+Nhg+NLpScl < 32.
*/
fast_float FilterUp(mem_float Imp[], mem_float ImpD[], UHWORD Nwing, BOOL Interp,
mem_float *Xp, double Ph, HWORD Inc);
fast_float FilterUD(mem_float Imp[], mem_float ImpD[], UHWORD Nwing, BOOL Interp,
mem_float *Xp, double Ph, HWORD Inc, double dhb);
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