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-
- /*
- * FILE: resample.h
- * BY: Julius Smith (at CCRMA, Stanford U)
- * C BY: translated from SAIL to C by Christopher Lee Fraley
- * (cf0v@andrew.cmu.edu)
- * DATE: 7-JUN-88
- * VERS: 2.0 (17-JUN-88, 3:00pm)
- */
-
- #define MAXNWING 5122
- #define MAXFACTOR 4 /* Maximum Factor without output buff overflow */
-
-
-
- /* Conversion constants */
- #define Nhc 8
- #define Na 7
- #define Np (Nhc+Na)
- #define Npc (1<<Nhc)
- #define Amask ((1<<Na)-1)
- #define Pmask ((1<<Np)-1)
- #define Nh 16
- #define Nb 16
- #define Nhxn 14
- #define Nhg (Nh-Nhxn)
- #define NLpScl 13
-
- /* 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.
- */
-
-