Automatically generate the bsinc table when building

This makes bsincgen a native tool like bin2h, so it can run automatically when
compiling.

2 files changed, 419 insertions, 0 deletions

diff --git a/native-tools/CMakeLists.txt b/native-tools/CMakeLists.txt
index bb8c677e..3c66c8bc 100644
--- a/native-tools/CMakeLists.txt
+++ b/native-tools/CMakeLists.txt
@@ -2,9 +2,24 @@ cmake_minimum_required(VERSION 3.0.2)
 
 project(native-tools)
 
+include(CheckLibraryExists)
+
+check_library_exists(m pow "" HAVE_LIBM)
+
 add_executable(bin2h bin2h.c)
 # Enforce no dressing for executable names, so the main script can find it
 set_target_properties(bin2h PROPERTIES OUTPUT_NAME bin2h)
 # Avoid configuration-dependent subdirectories while building with Visual Studio
 set_target_properties(bin2h PROPERTIES RUNTIME_OUTPUT_DIRECTORY_DEBUG "${CMAKE_BINARY_DIR}")
 set_target_properties(bin2h PROPERTIES RUNTIME_OUTPUT_DIRECTORY_RELEASE "${CMAKE_BINARY_DIR}")
+
+add_executable(bsincgen bsincgen.c)
+set_target_properties(bsincgen PROPERTIES OUTPUT_NAME bsincgen)
+set_target_properties(bsincgen PROPERTIES RUNTIME_OUTPUT_DIRECTORY_DEBUG "${CMAKE_BINARY_DIR}")
+set_target_properties(bsincgen PROPERTIES RUNTIME_OUTPUT_DIRECTORY_RELEASE "${CMAKE_BINARY_DIR}")
+if(HAVE_LIBM)
+    target_link_libraries(bsincgen m)
+endif(HAVE_LIBM)
+if(WIN32 AND CMAKE_COMPILER_IS_GNUCC)
+    set_property(TARGET bsincgen APPEND_STRING PROPERTY LINK_FLAGS " -municode")
+endif(WIN32 AND CMAKE_COMPILER_IS_GNUCC)
diff --git a/native-tools/bsincgen.c b/native-tools/bsincgen.c
new file mode 100644
index 00000000..754e0709
--- /dev/null
+++ b/native-tools/bsincgen.c
@@ -0,0 +1,404 @@
+/*

+ * Sinc interpolator coefficient and delta generator for the OpenAL Soft

+ * cross platform audio library.

+ *

+ * Copyright (C) 2015 by Christopher Fitzgerald.

+ *

+ * This library is free software; you can redistribute it and/or

+ * modify it under the terms of the GNU Library General Public

+ * License as published by the Free Software Foundation; either

+ * version 2 of the License, or (at your option) any later version.

+ *

+ * This library is distributed in the hope that it will be useful,

+ * but WITHOUT ANY WARRANTY; without even the implied warranty of

+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

+ * Library General Public License for more details.

+ *

+ * You should have received a copy of the GNU Library General Public

+ * License along with this library; if not, write to the Free Software

+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,

+ * MA 02110-1301  USA

+ *

+ * Or visit:  http://www.gnu.org/licenses/old-licenses/lgpl-2.0.html

+ *

+ * --------------------------------------------------------------------------

+ *

+ * This is a modified version of the bandlimited windowed sinc interpolator

+ * algorithm presented here:

+ *

+ *   Smith, J.O. "Windowed Sinc Interpolation", in

+ *   Physical Audio Signal Processing,

+ *   https://ccrma.stanford.edu/~jos/pasp/Windowed_Sinc_Interpolation.html,

+ *   online book,

+ *   accessed October 2012.

+ */

+

+#define _UNICODE

+#include <stdio.h>

+#include <math.h>

+#include <string.h>

+#include <stdlib.h>

+

+#include "../common/win_main_utf8.h"

+

+

+#ifndef M_PI

+#define M_PI                         (3.14159265358979323846)

+#endif

+

+#if defined(__ANDROID__) && !(defined(_ISOC99_SOURCE) || (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200112L))

+#define log2(x)  (log(x) / log(2.0))

+#endif

+

+// The number of distinct scale and phase intervals within the filter table.

+// Must be the same as in alu.h!

+#define BSINC_SCALE_COUNT (16)

+#define BSINC_PHASE_COUNT (16)

+

+/* 48 points includes the doubling for downsampling, so the maximum number of

+ * base sample points is 24, which is 23rd order.

+ */

+#define BSINC_POINTS_MAX (48)

+

+static double MinDouble(double a, double b)

+{ return (a <= b) ? a : b; }

+

+static double MaxDouble(double a, double b)

+{ return (a >= b) ? a : b; }

+

+/* NOTE: This is the normalized (instead of just sin(x)/x) cardinal sine

+ *       function.

+ *       2 f_t sinc(2 f_t x)

+ *       f_t -- normalized transition frequency (0.5 is nyquist)

+ *       x   -- sample index (-N to N)

+ */

+static double Sinc(const double x)

+{

+    if(fabs(x) < 1e-15)

+        return 1.0;

+    return sin(M_PI * x) / (M_PI * x);

+}

+

+static double BesselI_0(const double x)

+{

+    double term, sum, last_sum, x2, y;

+    int i;

+

+    term = 1.0;

+    sum = 1.0;

+    x2 = x / 2.0;

+    i = 1;

+

+    do {

+        y = x2 / i;

+        i++;

+        last_sum = sum;

+        term *= y * y;

+        sum += term;

+    } while(sum != last_sum);

+

+    return sum;

+}

+

+/* NOTE: k is assumed normalized (-1 to 1)

+ *       beta is equivalent to 2 alpha

+ */

+static double Kaiser(const double b, const double k)

+{

+    if(!(k >= -1.0 && k <= 1.0))

+        return 0.0;

+    return BesselI_0(b * sqrt(1.0 - k*k)) / BesselI_0(b);

+}

+

+/* Calculates the (normalized frequency) transition width of the Kaiser window.

+ * Rejection is in dB.

+ */

+static double CalcKaiserWidth(const double rejection, const int order)

+{

+    double w_t = 2.0 * M_PI;

+

+    if(rejection > 21.0)

+       return (rejection - 7.95) / (order * 2.285 * w_t);

+    /* This enforces a minimum rejection of just above 21.18dB */

+    return 5.79 / (order * w_t);

+}

+

+static double CalcKaiserBeta(const double rejection)

+{

+    if(rejection > 50.0)

+       return 0.1102 * (rejection - 8.7);

+    else if(rejection >= 21.0)

+       return (0.5842 * pow(rejection - 21.0, 0.4)) +

+              (0.07886 * (rejection - 21.0));

+    return 0.0;

+}

+

+/* Generates the coefficient, delta, and index tables required by the bsinc resampler */

+static void BsiGenerateTables(FILE *output, const char *tabname, const double rejection, const int order)

+{

+    static double   filter[BSINC_SCALE_COUNT][BSINC_PHASE_COUNT + 1][BSINC_POINTS_MAX];

+    static double scDeltas[BSINC_SCALE_COUNT][BSINC_PHASE_COUNT    ][BSINC_POINTS_MAX];

+    static double phDeltas[BSINC_SCALE_COUNT][BSINC_PHASE_COUNT + 1][BSINC_POINTS_MAX];

+    static double spDeltas[BSINC_SCALE_COUNT][BSINC_PHASE_COUNT    ][BSINC_POINTS_MAX];

+    static int mt[BSINC_SCALE_COUNT];

+    static double at[BSINC_SCALE_COUNT];

+    const int num_points_min = order + 1;

+    double width, beta, scaleBase, scaleRange;

+    int si, pi, i;

+

+    memset(filter, 0, sizeof(filter));

+    memset(scDeltas, 0, sizeof(scDeltas));

+    memset(phDeltas, 0, sizeof(phDeltas));

+    memset(spDeltas, 0, sizeof(spDeltas));

+

+    /* Calculate windowing parameters.  The width describes the transition

+       band, but it may vary due to the linear interpolation between scales

+       of the filter.

+    */

+    width = CalcKaiserWidth(rejection, order);

+    beta = CalcKaiserBeta(rejection);

+    scaleBase = width / 2.0;

+    scaleRange = 1.0 - scaleBase;

+

+    // Determine filter scaling.

+    for(si = 0; si < BSINC_SCALE_COUNT; si++)

+    {

+        const double scale = scaleBase + (scaleRange * si / (BSINC_SCALE_COUNT - 1));

+        const double a = MinDouble(floor(num_points_min / (2.0 * scale)), num_points_min);

+        const int m = 2 * (int)a;

+

+        mt[si] = m;

+        at[si] = a;

+    }

+

+    /* Calculate the Kaiser-windowed Sinc filter coefficients for each scale

+       and phase.

+    */

+    for(si = 0; si < BSINC_SCALE_COUNT; si++)

+    {

+        const int m = mt[si];

+        const int o = num_points_min - (m / 2);

+        const int l = (m / 2) - 1;

+        const double a = at[si];

+        const double scale = scaleBase + (scaleRange * si / (BSINC_SCALE_COUNT - 1));

+        const double cutoff = (0.5 * scale) - (scaleBase * MaxDouble(0.5, scale));

+

+        for(pi = 0; pi <= BSINC_PHASE_COUNT; pi++)

+        {

+            const double phase = l + ((double)pi / BSINC_PHASE_COUNT);

+

+            for(i = 0; i < m; i++)

+            {

+                const double x = i - phase;

+                filter[si][pi][o + i] = Kaiser(beta, x / a) * 2.0 * cutoff * Sinc(2.0 * cutoff * x);

+            }

+        }

+    }

+

+    /* Linear interpolation between scales is simplified by pre-calculating

+       the delta (b - a) in: x = a + f (b - a)

+

+       Given a difference in points between scales, the destination points

+       will be 0, thus: x = a + f (-a)

+    */

+    for(si = 0; si < (BSINC_SCALE_COUNT - 1); si++)

+    {

+        const int m = mt[si];

+        const int o = num_points_min - (m / 2);

+

+        for(pi = 0; pi < BSINC_PHASE_COUNT; pi++)

+        {

+            for(i = 0; i < m; i++)

+                scDeltas[si][pi][o + i] = filter[si + 1][pi][o + i] - filter[si][pi][o + i];

+        }

+    }

+

+    // Linear interpolation between phases is also simplified.

+    for(si = 0; si < BSINC_SCALE_COUNT; si++)

+    {

+        const int m = mt[si];

+        const int o = num_points_min - (m / 2);

+

+        for(pi = 0; pi < BSINC_PHASE_COUNT; pi++)

+        {

+            for(i = 0; i < m; i++)

+                phDeltas[si][pi][o + i] = filter[si][pi + 1][o + i] - filter[si][pi][o + i];

+        }

+    }

+

+    /* This last simplification is done to complete the bilinear equation for

+       the combination of scale and phase.

+    */

+    for(si = 0; si < (BSINC_SCALE_COUNT - 1); si++)

+    {

+        const int m = mt[si];

+        const int o = num_points_min - (m / 2);

+

+        for(pi = 0; pi < BSINC_PHASE_COUNT; pi++)

+        {

+            for(i = 0; i < m; i++)

+                spDeltas[si][pi][o + i] = phDeltas[si + 1][pi][o + i] - phDeltas[si][pi][o + i];

+        }

+    }

+

+    // Make sure the number of points is a multiple of 4 (for SIMD).

+    for(si = 0; si < BSINC_SCALE_COUNT; si++)

+        mt[si] = (mt[si]+3) & ~3;

+

+    fprintf(output,

+"/* This %d%s order filter has a rejection of -%.0fdB, yielding a transition width\n"

+" * of ~%.3f (normalized frequency). Order increases when downsampling to a\n"

+" * limit of one octave, after which the quality of the filter (transition\n"

+" * width) suffers to reduce the CPU cost. The bandlimiting will cut all sound\n"

+" * after downsampling by ~%.2f octaves.\n"

+" */\n"

+"const BSincTable %s = {\n",

+            order, (((order%100)/10) == 1) ? "th" :

+                   ((order%10) == 1) ? "st" :

+                   ((order%10) == 2) ? "nd" :

+                   ((order%10) == 3) ? "rd" : "th",

+            rejection, width, log2(1.0/scaleBase), tabname);

+

+    /* The scaleBase is calculated from the Kaiser window transition width.

+       It represents the absolute limit to the filter before it fully cuts

+       the signal.  The limit in octaves can be calculated by taking the

+       base-2 logarithm of its inverse: log_2(1 / scaleBase)

+    */

+    fprintf(output, "    /* scaleBase */ %.9ef, /* scaleRange */ %.9ef,\n", scaleBase, 1.0 / scaleRange);

+

+    fprintf(output, "    /* m */ {");

+    fprintf(output, " %d", mt[0]);

+    for(si = 1; si < BSINC_SCALE_COUNT; si++)

+        fprintf(output, ", %d", mt[si]);

+    fprintf(output, " },\n");

+

+    fprintf(output, "    /* filterOffset */ {");

+    fprintf(output, " %d", 0);

+    i = mt[0]*4*BSINC_PHASE_COUNT;

+    for(si = 1; si < BSINC_SCALE_COUNT; si++)

+    {

+        fprintf(output, ", %d", i);

+        i += mt[si]*4*BSINC_PHASE_COUNT;

+    }

+

+    fprintf(output, " },\n");

+

+    // Calculate the table size.

+    i = 0;

+    for(si = 0; si < BSINC_SCALE_COUNT; si++)

+        i += 4 * BSINC_PHASE_COUNT * mt[si];

+

+    fprintf(output, "\n    /* Tab (%d entries) */ {\n", i);

+    for(si = 0; si < BSINC_SCALE_COUNT; si++)

+    {

+        const int m = mt[si];

+        const int o = num_points_min - (m / 2);

+

+        for(pi = 0; pi < BSINC_PHASE_COUNT; pi++)

+        {

+            fprintf(output, "        /* %2d,%2d (%d) */", si, pi, m);

+            fprintf(output, "\n       ");

+            for(i = 0; i < m; i++)

+                fprintf(output, " %+14.9ef,", filter[si][pi][o + i]);

+            fprintf(output, "\n       ");

+            for(i = 0; i < m; i++)

+                fprintf(output, " %+14.9ef,", scDeltas[si][pi][o + i]);

+            fprintf(output, "\n       ");

+            for(i = 0; i < m; i++)

+                fprintf(output, " %+14.9ef,", phDeltas[si][pi][o + i]);

+            fprintf(output, "\n       ");

+            for(i = 0; i < m; i++)

+                fprintf(output, " %+14.9ef,", spDeltas[si][pi][o + i]);

+            fprintf(output, "\n");

+        }

+    }

+    fprintf(output, "    }\n};\n\n");

+}

+

+

+/* These methods generate a much simplified 4-point sinc interpolator using a

+ * Kaiser window. This is much simpler to process at run-time, but has notably

+ * more aliasing noise.

+ */

+

+/* Same as in alu.h! */

+#define FRACTIONBITS (12)

+#define FRACTIONONE  (1<<FRACTIONBITS)

+

+static void Sinc4GenerateTables(FILE *output, const double rejection)

+{

+    static double filter[FRACTIONONE][4];

+

+    const double width = CalcKaiserWidth(rejection, 3);

+    const double beta = CalcKaiserBeta(rejection);

+    const double scaleBase = width / 2.0;

+    const double scaleRange = 1.0 - scaleBase;

+    const double scale = scaleBase + scaleRange;

+    const double a = MinDouble(4.0, floor(4.0 / (2.0*scale)));

+    const int m = 2 * (int)a;

+    const int l = (m/2) - 1;

+    int pi;

+    for(pi = 0;pi < FRACTIONONE;pi++)

+    {

+        const double phase = l + ((double)pi / FRACTIONONE);

+        int i;

+

+        for(i = 0;i < m;i++)

+        {

+            double x = i - phase;

+            filter[pi][i] = Kaiser(beta, x / a) * Sinc(x);

+        }

+    }

+

+    fprintf(output, "alignas(16) static const float sinc4Tab[FRACTIONONE][4] = {\n");

+    for(pi = 0;pi < FRACTIONONE;pi++)

+        fprintf(output, "    { %+14.9ef, %+14.9ef, %+14.9ef, %+14.9ef },\n",

+                filter[pi][0], filter[pi][1], filter[pi][2], filter[pi][3]);

+    fprintf(output, "};\n\n");

+}

+

+

+int main(int argc, char *argv[])

+{

+    FILE *output;

+

+    if(argc > 2)

+    {

+        fprintf(stderr, "Usage: %s [output file]\n", argv[0]);

+        return 1;

+    }

+

+    if(argc == 2)

+    {

+        output = fopen(argv[1], "wb");

+        if(!output)

+        {

+            fprintf(stderr, "Failed to open %s for writing\n", argv[1]);

+            return 1;

+        }

+    }

+    else

+        output = stdout;

+

+    fprintf(output, "/* Generated by bsincgen, do not edit! */\n\n"

+"static_assert(BSINC_SCALE_COUNT == %d, \"Unexpected BSINC_SCALE_COUNT value!\");\n"

+"static_assert(BSINC_PHASE_COUNT == %d, \"Unexpected BSINC_PHASE_COUNT value!\");\n"

+"static_assert(FRACTIONONE == %d, \"Unexpected FRACTIONONE value!\");\n\n"

+"typedef struct BSincTable {\n"

+"    const float scaleBase, scaleRange;\n"

+"    const int m[BSINC_SCALE_COUNT];\n"

+"    const int filterOffset[BSINC_SCALE_COUNT];\n"

+"    alignas(16) const float Tab[];\n"

+"} BSincTable;\n\n", BSINC_SCALE_COUNT, BSINC_PHASE_COUNT, FRACTIONONE);

+    /* A 23rd order filter with a -60dB drop at nyquist. */

+    BsiGenerateTables(output, "bsinc24", 60.0, 23);

+    /* An 11th order filter with a -60dB drop at nyquist. */

+    BsiGenerateTables(output, "bsinc12", 60.0, 11);

+    Sinc4GenerateTables(output, 60.0);

+

+    if(output != stdout)

+        fclose(output);

+    output = NULL;

+

+    return 0;

+}