diff --git a/libavcodec/opusenc_psy.c b/libavcodec/opusenc_psy.c
index 7c356fc568..e6858f1856 100644
--- a/libavcodec/opusenc_psy.c
+++ b/libavcodec/opusenc_psy.c
@@ -507,7 +507,7 @@ av_cold int ff_opus_psy_init(OpusPsyContext *s, AVCodecContext *avctx,
             ret = AVERROR(ENOMEM);
             goto fail;
         }
-        ff_generate_window_func(s->window[i], 2*len, WFUNC_SINE, &tmp);
+        generate_window_func(s->window[i], 2*len, WFUNC_SINE, &tmp);
         if ((ret = ff_mdct15_init(&s->mdct[i], 0, i + 3, 68 << (CELT_BLOCK_NB - 1 - i))))
             goto fail;
     }
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 98acb51bcb..9eeb7d218f 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -37,7 +37,7 @@ OBJS-$(CONFIG_AECHO_FILTER)                  += af_aecho.o
 OBJS-$(CONFIG_AEMPHASIS_FILTER)              += af_aemphasis.o
 OBJS-$(CONFIG_AEVAL_FILTER)                  += aeval.o
 OBJS-$(CONFIG_AFADE_FILTER)                  += af_afade.o
-OBJS-$(CONFIG_AFFTFILT_FILTER)               += af_afftfilt.o window_func.o
+OBJS-$(CONFIG_AFFTFILT_FILTER)               += af_afftfilt.o
 OBJS-$(CONFIG_AFIR_FILTER)                   += af_afir.o
 OBJS-$(CONFIG_AFORMAT_FILTER)                += af_aformat.o
 OBJS-$(CONFIG_AGATE_FILTER)                  += af_agate.o
@@ -369,13 +369,13 @@ OBJS-$(CONFIG_APHASEMETER_FILTER)            += avf_aphasemeter.o
 OBJS-$(CONFIG_AVECTORSCOPE_FILTER)           += avf_avectorscope.o
 OBJS-$(CONFIG_CONCAT_FILTER)                 += avf_concat.o
 OBJS-$(CONFIG_SHOWCQT_FILTER)                += avf_showcqt.o lswsutils.o lavfutils.o
-OBJS-$(CONFIG_SHOWFREQS_FILTER)              += avf_showfreqs.o window_func.o
-OBJS-$(CONFIG_SHOWSPECTRUM_FILTER)           += avf_showspectrum.o window_func.o
-OBJS-$(CONFIG_SHOWSPECTRUMPIC_FILTER)        += avf_showspectrum.o window_func.o
+OBJS-$(CONFIG_SHOWFREQS_FILTER)              += avf_showfreqs.o
+OBJS-$(CONFIG_SHOWSPECTRUM_FILTER)           += avf_showspectrum.o
+OBJS-$(CONFIG_SHOWSPECTRUMPIC_FILTER)        += avf_showspectrum.o
 OBJS-$(CONFIG_SHOWVOLUME_FILTER)             += avf_showvolume.o
 OBJS-$(CONFIG_SHOWWAVES_FILTER)              += avf_showwaves.o
 OBJS-$(CONFIG_SHOWWAVESPIC_FILTER)           += avf_showwaves.o
-OBJS-$(CONFIG_SPECTRUMSYNTH_FILTER)          += vaf_spectrumsynth.o window_func.o
+OBJS-$(CONFIG_SPECTRUMSYNTH_FILTER)          += vaf_spectrumsynth.o
 
 # multimedia sources
 OBJS-$(CONFIG_AMOVIE_FILTER)                 += src_movie.o
diff --git a/libavfilter/af_afftfilt.c b/libavfilter/af_afftfilt.c
index d166fa4190..52755a1fb4 100644
--- a/libavfilter/af_afftfilt.c
+++ b/libavfilter/af_afftfilt.c
@@ -166,7 +166,7 @@ static int config_input(AVFilterLink *inlink)
                                       sizeof(*s->window_func_lut));
     if (!s->window_func_lut)
         return AVERROR(ENOMEM);
-    ff_generate_window_func(s->window_func_lut, s->window_size, s->win_func, &overlap);
+    generate_window_func(s->window_func_lut, s->window_size, s->win_func, &overlap);
     if (s->overlap == 1)
         s->overlap = overlap;
 
diff --git a/libavfilter/avf_showfreqs.c b/libavfilter/avf_showfreqs.c
index 068ff1fb88..22f28ec387 100644
--- a/libavfilter/avf_showfreqs.c
+++ b/libavfilter/avf_showfreqs.c
@@ -218,7 +218,7 @@ static int config_output(AVFilterLink *outlink)
                                       sizeof(*s->window_func_lut));
     if (!s->window_func_lut)
         return AVERROR(ENOMEM);
-    ff_generate_window_func(s->window_func_lut, s->win_size, s->win_func, &overlap);
+    generate_window_func(s->window_func_lut, s->win_size, s->win_func, &overlap);
     if (s->overlap == 1.)
         s->overlap = overlap;
     s->hop_size = (1. - s->overlap) * s->win_size;
diff --git a/libavfilter/avf_showspectrum.c b/libavfilter/avf_showspectrum.c
index 4317161d79..956f62f3ad 100644
--- a/libavfilter/avf_showspectrum.c
+++ b/libavfilter/avf_showspectrum.c
@@ -403,7 +403,7 @@ static int config_output(AVFilterLink *outlink)
                          sizeof(*s->window_func_lut));
         if (!s->window_func_lut)
             return AVERROR(ENOMEM);
-        ff_generate_window_func(s->window_func_lut, s->win_size, s->win_func, &overlap);
+        generate_window_func(s->window_func_lut, s->win_size, s->win_func, &overlap);
         if (s->overlap == 1)
             s->overlap = overlap;
         s->hop_size = (1. - s->overlap) * s->win_size;
diff --git a/libavfilter/vaf_spectrumsynth.c b/libavfilter/vaf_spectrumsynth.c
index ed191a3e34..fed2cbba03 100644
--- a/libavfilter/vaf_spectrumsynth.c
+++ b/libavfilter/vaf_spectrumsynth.c
@@ -210,7 +210,7 @@ static int config_output(AVFilterLink *outlink)
                                       sizeof(*s->window_func_lut));
     if (!s->window_func_lut)
         return AVERROR(ENOMEM);
-    ff_generate_window_func(s->window_func_lut, s->win_size, s->win_func, &overlap);
+    generate_window_func(s->window_func_lut, s->win_size, s->win_func, &overlap);
     if (s->overlap == 1)
         s->overlap = overlap;
     s->hop_size = (1 - s->overlap) * s->win_size;
diff --git a/libavfilter/window_func.c b/libavfilter/window_func.c
deleted file mode 100644
index acf1b20847..0000000000
--- a/libavfilter/window_func.c
+++ /dev/null
@@ -1,178 +0,0 @@
-/*
- * Copyright (c) 2015 Paul B Mahol
- *
- * This file is part of FFmpeg.
- *
- * FFmpeg is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; either
- * version 2.1 of the License, or (at your option) any later version.
- *
- * FFmpeg 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
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with FFmpeg; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
- */
-
-#include <math.h>
-
-#include "libavutil/avassert.h"
-#include "window_func.h"
-
-void ff_generate_window_func(float *lut, int N, int win_func, float *overlap)
-{
-    int n;
-
-    switch (win_func) {
-    case WFUNC_RECT:
-        for (n = 0; n < N; n++)
-            lut[n] = 1.;
-        *overlap = 0.;
-        break;
-    case WFUNC_BARTLETT:
-        for (n = 0; n < N; n++)
-            lut[n] = 1.-fabs((n-(N-1)/2.)/((N-1)/2.));
-        *overlap = 0.5;
-        break;
-    case WFUNC_HANNING:
-        for (n = 0; n < N; n++)
-            lut[n] = .5*(1-cos(2*M_PI*n/(N-1)));
-        *overlap = 0.5;
-        break;
-    case WFUNC_HAMMING:
-        for (n = 0; n < N; n++)
-            lut[n] = .54-.46*cos(2*M_PI*n/(N-1));
-        *overlap = 0.5;
-        break;
-    case WFUNC_BLACKMAN:
-        for (n = 0; n < N; n++)
-            lut[n] = .42659-.49656*cos(2*M_PI*n/(N-1))+.076849*cos(4*M_PI*n/(N-1));
-        *overlap = 0.661;
-        break;
-    case WFUNC_WELCH:
-        for (n = 0; n < N; n++)
-            lut[n] = 1.-(n-(N-1)/2.)/((N-1)/2.)*(n-(N-1)/2.)/((N-1)/2.);
-        *overlap = 0.293;
-        break;
-    case WFUNC_FLATTOP:
-        for (n = 0; n < N; n++)
-            lut[n] = 1.-1.985844164102*cos( 2*M_PI*n/(N-1))+1.791176438506*cos( 4*M_PI*n/(N-1))-
-                        1.282075284005*cos( 6*M_PI*n/(N-1))+0.667777530266*cos( 8*M_PI*n/(N-1))-
-                        0.240160796576*cos(10*M_PI*n/(N-1))+0.056656381764*cos(12*M_PI*n/(N-1))-
-                        0.008134974479*cos(14*M_PI*n/(N-1))+0.000624544650*cos(16*M_PI*n/(N-1))-
-                        0.000019808998*cos(18*M_PI*n/(N-1))+0.000000132974*cos(20*M_PI*n/(N-1));
-        *overlap = 0.841;
-        break;
-    case WFUNC_BHARRIS:
-        for (n = 0; n < N; n++)
-            lut[n] = 0.35875-0.48829*cos(2*M_PI*n/(N-1))+0.14128*cos(4*M_PI*n/(N-1))-0.01168*cos(6*M_PI*n/(N-1));
-        *overlap = 0.661;
-        break;
-    case WFUNC_BNUTTALL:
-        for (n = 0; n < N; n++)
-            lut[n] = 0.3635819-0.4891775*cos(2*M_PI*n/(N-1))+0.1365995*cos(4*M_PI*n/(N-1))-0.0106411*cos(6*M_PI*n/(N-1));
-        *overlap = 0.661;
-        break;
-    case WFUNC_BHANN:
-        for (n = 0; n < N; n++)
-            lut[n] = 0.62-0.48*fabs(n/(double)(N-1)-.5)-0.38*cos(2*M_PI*n/(N-1));
-        *overlap = 0.5;
-        break;
-    case WFUNC_SINE:
-        for (n = 0; n < N; n++)
-            lut[n] = sin(M_PI*n/(N-1));
-        *overlap = 0.75;
-        break;
-    case WFUNC_NUTTALL:
-        for (n = 0; n < N; n++)
-            lut[n] = 0.355768-0.487396*cos(2*M_PI*n/(N-1))+0.144232*cos(4*M_PI*n/(N-1))-0.012604*cos(6*M_PI*n/(N-1));
-        *overlap = 0.663;
-        break;
-    case WFUNC_LANCZOS:
-#define SINC(x) (!(x)) ? 1 : sin(M_PI * (x))/(M_PI * (x));
-        for (n = 0; n < N; n++)
-            lut[n] = SINC((2.*n)/(N-1)-1);
-        *overlap = 0.75;
-        break;
-    case WFUNC_GAUSS:
-#define SQR(x) ((x)*(x))
-        for (n = 0; n < N; n++)
-            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;
-    case WFUNC_DOLPH: {
-        double b = cosh(7.6009022095419887 / (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;
-    case WFUNC_CAUCHY:
-        for (n = 0; n < N; n++) {
-            double x = 2 * ((n / (double)(N - 1)) - .5);
-
-            if (x <= -.5 || x >= .5) {
-                lut[n] = 0;
-            } else {
-                lut[n] = FFMIN(1, fabs(1/(1+4*16*x*x)));
-            }
-        }
-        *overlap = 0.75;
-        break;
-    case WFUNC_PARZEN:
-        for (n = 0; n < N; n++) {
-            double x = 2 * ((n / (double)(N - 1)) - .5);
-
-            if (x > 0.25 && x <= 0.5) {
-                lut[n] = -2 * powf(-1 + 2 * x, 3);
-            } else if (x >= -.5 && x < -.25) {
-                lut[n] = 2 * powf(1 + 2 * x, 3);
-            } else if (x >= -.25 && x < 0) {
-                lut[n] = 1 - 24 * x * x - 48 * x * x * x;
-            } else if (x >= 0 && x <= .25) {
-                lut[n] = 1 - 24 * x * x + 48 * x * x * x;
-            } else {
-                lut[n] = 0;
-            }
-        }
-        *overlap = 0.75;
-        break;
-    case WFUNC_POISSON:
-        for (n = 0; n < N; n++) {
-            double x = 2 * ((n / (double)(N - 1)) - .5);
-
-            if (x >= 0 && x <= .5) {
-                lut[n] = exp(-6*x);
-            } else if (x < 0 && x >= -.5) {
-                lut[n] = exp(6*x);
-            } else {
-                lut[n] = 0;
-            }
-        }
-        *overlap = 0.75;
-        break;
-    default:
-        av_assert0(0);
-    }
-}
diff --git a/libavfilter/window_func.h b/libavfilter/window_func.h
index 4611498d47..a94482c937 100644
--- a/libavfilter/window_func.h
+++ b/libavfilter/window_func.h
@@ -22,6 +22,9 @@
 #ifndef AVFILTER_WINDOW_FUNC_H
 #define AVFILTER_WINDOW_FUNC_H
 
+#include <math.h>
+#include "libavutil/avassert.h"
+
 enum WindowFunc     { WFUNC_RECT, WFUNC_HANNING, WFUNC_HAMMING, WFUNC_BLACKMAN,
                       WFUNC_BARTLETT, WFUNC_WELCH, WFUNC_FLATTOP,
                       WFUNC_BHARRIS, WFUNC_BNUTTALL, WFUNC_SINE, WFUNC_NUTTALL,
@@ -29,6 +32,159 @@ enum WindowFunc     { WFUNC_RECT, WFUNC_HANNING, WFUNC_HAMMING, WFUNC_BLACKMAN,
                       WFUNC_DOLPH, WFUNC_CAUCHY, WFUNC_PARZEN, WFUNC_POISSON,
                       NB_WFUNC };
 
-void ff_generate_window_func(float *lut, int N, int win_func, float *overlap);
+static inline void generate_window_func(float *lut, int N, int win_func,
+                                        float *overlap)
+{
+    int n;
+
+    switch (win_func) {
+    case WFUNC_RECT:
+        for (n = 0; n < N; n++)
+            lut[n] = 1.;
+        *overlap = 0.;
+        break;
+    case WFUNC_BARTLETT:
+        for (n = 0; n < N; n++)
+            lut[n] = 1.-fabs((n-(N-1)/2.)/((N-1)/2.));
+        *overlap = 0.5;
+        break;
+    case WFUNC_HANNING:
+        for (n = 0; n < N; n++)
+            lut[n] = .5*(1-cos(2*M_PI*n/(N-1)));
+        *overlap = 0.5;
+        break;
+    case WFUNC_HAMMING:
+        for (n = 0; n < N; n++)
+            lut[n] = .54-.46*cos(2*M_PI*n/(N-1));
+        *overlap = 0.5;
+        break;
+    case WFUNC_BLACKMAN:
+        for (n = 0; n < N; n++)
+            lut[n] = .42659-.49656*cos(2*M_PI*n/(N-1))+.076849*cos(4*M_PI*n/(N-1));
+        *overlap = 0.661;
+        break;
+    case WFUNC_WELCH:
+        for (n = 0; n < N; n++)
+            lut[n] = 1.-(n-(N-1)/2.)/((N-1)/2.)*(n-(N-1)/2.)/((N-1)/2.);
+        *overlap = 0.293;
+        break;
+    case WFUNC_FLATTOP:
+        for (n = 0; n < N; n++)
+            lut[n] = 1.-1.985844164102*cos( 2*M_PI*n/(N-1))+1.791176438506*cos( 4*M_PI*n/(N-1))-
+            1.282075284005*cos( 6*M_PI*n/(N-1))+0.667777530266*cos( 8*M_PI*n/(N-1))-
+            0.240160796576*cos(10*M_PI*n/(N-1))+0.056656381764*cos(12*M_PI*n/(N-1))-
+            0.008134974479*cos(14*M_PI*n/(N-1))+0.000624544650*cos(16*M_PI*n/(N-1))-
+            0.000019808998*cos(18*M_PI*n/(N-1))+0.000000132974*cos(20*M_PI*n/(N-1));
+        *overlap = 0.841;
+        break;
+    case WFUNC_BHARRIS:
+        for (n = 0; n < N; n++)
+            lut[n] = 0.35875-0.48829*cos(2*M_PI*n/(N-1))+0.14128*cos(4*M_PI*n/(N-1))-0.01168*cos(6*M_PI*n/(N-1));
+        *overlap = 0.661;
+        break;
+    case WFUNC_BNUTTALL:
+        for (n = 0; n < N; n++)
+            lut[n] = 0.3635819-0.4891775*cos(2*M_PI*n/(N-1))+0.1365995*cos(4*M_PI*n/(N-1))-0.0106411*cos(6*M_PI*n/(N-1));
+        *overlap = 0.661;
+        break;
+    case WFUNC_BHANN:
+        for (n = 0; n < N; n++)
+            lut[n] = 0.62-0.48*fabs(n/(double)(N-1)-.5)-0.38*cos(2*M_PI*n/(N-1));
+        *overlap = 0.5;
+        break;
+    case WFUNC_SINE:
+        for (n = 0; n < N; n++)
+            lut[n] = sin(M_PI*n/(N-1));
+        *overlap = 0.75;
+        break;
+    case WFUNC_NUTTALL:
+        for (n = 0; n < N; n++)
+            lut[n] = 0.355768-0.487396*cos(2*M_PI*n/(N-1))+0.144232*cos(4*M_PI*n/(N-1))-0.012604*cos(6*M_PI*n/(N-1));
+        *overlap = 0.663;
+        break;
+    case WFUNC_LANCZOS:
+        #define SINC(x) (!(x)) ? 1 : sin(M_PI * (x))/(M_PI * (x));
+        for (n = 0; n < N; n++)
+            lut[n] = SINC((2.*n)/(N-1)-1);
+        *overlap = 0.75;
+        break;
+    case WFUNC_GAUSS:
+        #define SQR(x) ((x)*(x))
+        for (n = 0; n < N; n++)
+            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;
+    case WFUNC_DOLPH: {
+        double b = cosh(7.6009022095419887 / (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;
+    case WFUNC_CAUCHY:
+        for (n = 0; n < N; n++) {
+            double x = 2 * ((n / (double)(N - 1)) - .5);
+
+            if (x <= -.5 || x >= .5) {
+                lut[n] = 0;
+            } else {
+                lut[n] = FFMIN(1, fabs(1/(1+4*16*x*x)));
+            }
+        }
+        *overlap = 0.75;
+        break;
+    case WFUNC_PARZEN:
+        for (n = 0; n < N; n++) {
+            double x = 2 * ((n / (double)(N - 1)) - .5);
+
+            if (x > 0.25 && x <= 0.5) {
+                lut[n] = -2 * powf(-1 + 2 * x, 3);
+            } else if (x >= -.5 && x < -.25) {
+                lut[n] = 2 * powf(1 + 2 * x, 3);
+            } else if (x >= -.25 && x < 0) {
+                lut[n] = 1 - 24 * x * x - 48 * x * x * x;
+            } else if (x >= 0 && x <= .25) {
+                lut[n] = 1 - 24 * x * x + 48 * x * x * x;
+            } else {
+                lut[n] = 0;
+            }
+        }
+        *overlap = 0.75;
+        break;
+    case WFUNC_POISSON:
+        for (n = 0; n < N; n++) {
+            double x = 2 * ((n / (double)(N - 1)) - .5);
+
+            if (x >= 0 && x <= .5) {
+                lut[n] = exp(-6*x);
+            } else if (x < 0 && x >= -.5) {
+                lut[n] = exp(6*x);
+            } else {
+                lut[n] = 0;
+            }
+        }
+        *overlap = 0.75;
+        break;
+    default:
+        av_assert0(0);
+    }
+}
 
 #endif /* AVFILTER_WINDOW_FUNC_H */