Pre-compute the sinc4 resampler coefficient table

1 files changed, 0 insertions, 92 deletions

diff --git a/Alc/mixer.c b/Alc/mixer.c
index 69e52a6e..f4374882 100644
--- a/Alc/mixer.c
+++ b/Alc/mixer.c
@@ -43,8 +43,6 @@ static_assert((INT_MAX>>FRACTIONBITS)/MAX_PITCH > BUFFERSIZE,
 
 extern inline void InitiatePositionArrays(ALuint frac, ALint increment, ALuint *restrict frac_arr, ALint *restrict pos_arr, ALsizei size);
 
-alignas(16) ALfloat ResampleCoeffs_FIR4[FRACTIONONE][4];
-
 
 enum Resampler {
     PointResampler,
@@ -155,91 +153,10 @@ static inline ResamplerFunc SelectResampler(enum Resampler resampler)
 }
 
 
-/* The sinc resampler makes use of a Kaiser window to limit the needed sample
- * points to 4.
- */
-
-#ifndef M_PI
-#define M_PI                         (3.14159265358979323846)
-#endif
-static inline double Sinc(double x)
-{
-    if(x == 0.0) return 1.0;
-    return sin(x*M_PI) / (x*M_PI);
-}
-
-/* The zero-order modified Bessel function of the first kind, used for the
- * Kaiser window.
- *
- *   I_0(x) = sum_{k=0}^inf (1 / k!)^2 (x / 2)^(2 k)
- *          = sum_{k=0}^inf ((x / 2)^k / k!)^2
- */
-static double BesselI_0(double x)
-{
-    double term, sum, x2, y, last_sum;
-    int k;
-
-    /* Start at k=1 since k=0 is trivial. */
-    term = 1.0;
-    sum = 1.0;
-    x2 = x / 2.0;
-    k = 1;
-
-    /* Let the integration converge until the term of the sum is no longer
-     * significant.
-     */
-    do {
-        y = x2 / k;
-        k ++;
-        last_sum = sum;
-        term *= y * y;
-        sum += term;
-    } while(sum != last_sum);
-    return sum;
-}
-
-/* Calculate a Kaiser window from the given beta value and a normalized k
- * [-1, 1].
- *
- *   w(k) = { I_0(B sqrt(1 - k^2)) / I_0(B),  -1 <= k <= 1
- *          { 0,                              elsewhere.
- *
- * Where k can be calculated as:
- *
- *   k = i / l,         where -l <= i <= l.
- *
- * or:
- *
- *   k = 2 i / M - 1,   where 0 <= i <= M.
- */
-static inline double Kaiser(double b, double k)
-{
-    if(k <= -1.0 || k >= 1.0) return 0.0;
-    return BesselI_0(b * sqrt(1.0 - (k*k))) / BesselI_0(b);
-}
-
-static inline double CalcKaiserBeta(double rejection)
-{
-    if(rejection > 50.0)
-        return 0.1102 * (rejection - 8.7);
-    if(rejection >= 21.0)
-        return (0.5842 * pow(rejection - 21.0, 0.4)) +
-               (0.07886 * (rejection - 21.0));
-    return 0.0;
-}
-
-static float SincKaiser(double r, double x)
-{
-    /* Limit rippling to -60dB. */
-    return (float)(Kaiser(CalcKaiserBeta(60.0), x / r) * Sinc(x));
-}
-
-
 void aluInitMixer(void)
 {
     enum Resampler resampler = ResamplerDefault;
     const char *str;
-    ALuint i;
 
     if(ConfigValueStr(NULL, NULL, "resampler", &str))
     {
@@ -267,15 +184,6 @@ void aluInitMixer(void)
         }
     }
 
-    for(i = 0;i < FRACTIONONE;i++)
-    {
-        ALdouble mu = (ALdouble)i / FRACTIONONE;
-        ResampleCoeffs_FIR4[i][0] = SincKaiser(2.0, mu - -1.0);
-        ResampleCoeffs_FIR4[i][1] = SincKaiser(2.0, mu -  0.0);
-        ResampleCoeffs_FIR4[i][2] = SincKaiser(2.0, mu -  1.0);
-        ResampleCoeffs_FIR4[i][3] = SincKaiser(2.0, mu -  2.0);
-    }
-
     MixHrtfSamples = SelectHrtfMixer();
     MixSamples = SelectMixer();
     ResampleSamples = SelectResampler(resampler);