avfilter/window_func: add dolph window

1 files changed, 12 insertions, 0 deletions

diff --git a/libavfilter/window_func.c b/libavfilter/window_func.c
index 9c6202aa18..1931c8ea65 100644
--- a/libavfilter/window_func.c
+++ b/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);
     }