avfilter/window_func: add dolph window

doc/filters.texi

@@ -16518,6 +16518,7 @@ It accepts the following values:
 @item lanczos
 @item gauss
 @item tukey
+@item dolph
 @end table
 Default is @code{hanning}.
 
@@ -16665,6 +16666,7 @@ It accepts the following values:
 @item lanczos
 @item gauss
 @item tukey
+@item dolph
 @end table
 
 Default value is @code{hann}.
@@ -16808,6 +16810,7 @@ It accepts the following values:
 @item lanczos
 @item gauss
 @item tukey
+@item dolph
 @end table
 Default value is @code{hann}.
 

libavfilter/avf_showfreqs.c

@@ -112,6 +112,7 @@ static const AVOption showfreqs_options[] = {
         { "lanczos",  "Lanczos",          0, AV_OPT_TYPE_CONST, {.i64=WFUNC_LANCZOS},  0, 0, FLAGS, "win_func" },
         { "gauss",    "Gauss",            0, AV_OPT_TYPE_CONST, {.i64=WFUNC_GAUSS},    0, 0, FLAGS, "win_func" },
         { "tukey",    "Tukey",            0, AV_OPT_TYPE_CONST, {.i64=WFUNC_TUKEY},    0, 0, FLAGS, "win_func" },
+        { "dolph",    "Dolph-Chebyshev",  0, AV_OPT_TYPE_CONST, {.i64=WFUNC_DOLPH},    0, 0, FLAGS, "win_func" },
     { "overlap",  "set window overlap", OFFSET(overlap), AV_OPT_TYPE_FLOAT, {.dbl=1.}, 0., 1., FLAGS },
     { "averaging", "set time averaging", OFFSET(avg), AV_OPT_TYPE_INT, {.i64=1}, 0, INT32_MAX, FLAGS },
     { "colors", "set channels colors", OFFSET(colors), AV_OPT_TYPE_STRING, {.str = "red|green|blue|yellow|orange|lime|pink|magenta|brown" }, 0, 0, FLAGS },

libavfilter/avf_showspectrum.c

@@ -133,6 +133,7 @@ static const AVOption showspectrum_options[] = {
         { "lanczos",  "Lanczos",          0, AV_OPT_TYPE_CONST, {.i64=WFUNC_LANCZOS},  0, 0, FLAGS, "win_func" },
         { "gauss",    "Gauss",            0, AV_OPT_TYPE_CONST, {.i64=WFUNC_GAUSS},    0, 0, FLAGS, "win_func" },
         { "tukey",    "Tukey",            0, AV_OPT_TYPE_CONST, {.i64=WFUNC_TUKEY},    0, 0, FLAGS, "win_func" },
+        { "dolph",    "Dolph-Chebyshev",  0, AV_OPT_TYPE_CONST, {.i64=WFUNC_DOLPH},    0, 0, FLAGS, "win_func" },
     { "orientation", "set orientation", OFFSET(orientation), AV_OPT_TYPE_INT, {.i64=VERTICAL}, 0, NB_ORIENTATIONS-1, FLAGS, "orientation" },
         { "vertical",   NULL, 0, AV_OPT_TYPE_CONST, {.i64=VERTICAL},   0, 0, FLAGS, "orientation" },
         { "horizontal", NULL, 0, AV_OPT_TYPE_CONST, {.i64=HORIZONTAL}, 0, 0, FLAGS, "orientation" },
@@ -942,6 +943,7 @@ static const AVOption showspectrumpic_options[] = {
         { "lanczos",  "Lanczos",          0, AV_OPT_TYPE_CONST, {.i64=WFUNC_LANCZOS},  0, 0, FLAGS, "win_func" },
         { "gauss",    "Gauss",            0, AV_OPT_TYPE_CONST, {.i64=WFUNC_GAUSS},    0, 0, FLAGS, "win_func" },
         { "tukey",    "Tukey",            0, AV_OPT_TYPE_CONST, {.i64=WFUNC_TUKEY},    0, 0, FLAGS, "win_func" },
+        { "dolph",    "Dolph-Chebyshev",  0, AV_OPT_TYPE_CONST, {.i64=WFUNC_DOLPH},    0, 0, FLAGS, "win_func" },
     { "orientation", "set orientation", OFFSET(orientation), AV_OPT_TYPE_INT, {.i64=VERTICAL}, 0, NB_ORIENTATIONS-1, FLAGS, "orientation" },
         { "vertical",   NULL, 0, AV_OPT_TYPE_CONST, {.i64=VERTICAL},   0, 0, FLAGS, "orientation" },
         { "horizontal", NULL, 0, AV_OPT_TYPE_CONST, {.i64=HORIZONTAL}, 0, 0, FLAGS, "orientation" },

libavfilter/window_func.c

@@ -116,6 +116,18 @@ void ff_generate_window_func(float *lut, int N, int win_func, float *overlap)
         }
         *overlap = 0.33;
         break;
+    case WFUNC_DOLPH: {
+        double b = cosh(acosh(pow(10., 3)) / (N-1)), sum, t, c, norm = 0;
+        int j;
+        for (c = 1 - 1 / (b*b), n = (N-1) / 2; n >= 0; --n) {
+            for (sum = !n, b = t = j = 1; j <= n && sum != t; b *= (n-j) * (1./j), ++j)
+                t = sum, sum += (b *= c * (N - n - j) * (1./j));
+            sum /= (N - 1 - n), sum /= (norm = norm ? norm : sum);
+            lut[n] = sum;
+            lut[N - 1 - n] = sum;
+        }
+        *overlap = 0.5;}
+        break;
     default:
         av_assert0(0);
     }

libavfilter/window_func.h

@@ -25,7 +25,8 @@
 enum WindowFunc     { WFUNC_RECT, WFUNC_HANNING, WFUNC_HAMMING, WFUNC_BLACKMAN,
                       WFUNC_BARTLETT, WFUNC_WELCH, WFUNC_FLATTOP,
                       WFUNC_BHARRIS, WFUNC_BNUTTALL, WFUNC_SINE, WFUNC_NUTTALL,
-                      WFUNC_BHANN, WFUNC_LANCZOS, WFUNC_GAUSS, WFUNC_TUKEY, NB_WFUNC };
+                      WFUNC_BHANN, WFUNC_LANCZOS, WFUNC_GAUSS, WFUNC_TUKEY,
+                      WFUNC_DOLPH, NB_WFUNC };
 
 void ff_generate_window_func(float *lut, int N, int win_func, float *overlap);