avfilter/window_func: add tukey window function

Signed-off-by: Paul B Mahol <onemda@gmail.com>

doc/filters.texi

@@ -14535,6 +14535,7 @@ It accepts the following values:
 @item nuttall
 @item lanczos
 @item gauss
+@item tukey
 @end table
 Default is @code{hanning}.
 
@@ -14678,6 +14679,7 @@ It accepts the following values:
 @item nuttall
 @item lanczos
 @item gauss
+@item tukey
 @end table
 
 Default value is @code{hann}.

libavfilter/avf_showfreqs.c

@@ -111,6 +111,7 @@ static const AVOption showfreqs_options[] = {
         { "nuttall",  "Nuttall",          0, AV_OPT_TYPE_CONST, {.i64=WFUNC_NUTTALL},  0, 0, FLAGS, "win_func" },
         { "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" },
     { "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

@@ -123,6 +123,7 @@ static const AVOption showspectrum_options[] = {
         { "nuttall",  "Nuttall",          0, AV_OPT_TYPE_CONST, {.i64=WFUNC_NUTTALL},  0, 0, FLAGS, "win_func" },
         { "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" },
     { "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" },
@@ -826,6 +827,7 @@ static const AVOption showspectrumpic_options[] = {
         { "nuttall",  "Nuttall",          0, AV_OPT_TYPE_CONST, {.i64=WFUNC_NUTTALL},  0, 0, FLAGS, "win_func" },
         { "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" },
     { "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

@@ -104,6 +104,18 @@ void ff_generate_window_func(float *lut, int N, int win_func, float *overlap)
             lut[n] = exp(-0.5 * SQR((n-(N-1)/2)/(0.4*(N-1)/2.f)));
         *overlap = 0.75;
         break;
+    case WFUNC_TUKEY:
+        for (n = 0; n < N; n++) {
+            float M = (N-1)/2.;
+
+            if (FFABS(n - M) >= 0.3 * M) {
+                lut[n] = 0.5 * (1 + cos((M_PI*(FFABS(n - M) - 0.3 * M))/((1 - 0.3) * M)));
+            } else {
+                lut[n] = 1;
+            }
+        }
+        *overlap = 0.33;
+        break;
     default:
         av_assert0(0);
     }

libavfilter/window_func.h

@@ -25,7 +25,7 @@
 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, NB_WFUNC };
+                      WFUNC_BHANN, WFUNC_LANCZOS, WFUNC_GAUSS, WFUNC_TUKEY, NB_WFUNC };
 
 void ff_generate_window_func(float *lut, int N, int win_func, float *overlap);