diff --git a/doc/filters.texi b/doc/filters.texi
index 5e7326d2f2..4a28c1f828 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -21731,6 +21731,21 @@ Threshold used depends also on each decomposition coefficients.
 Default is universal.
 @end table
 
+@section varblur
+Apply variable blur filter by using 2nd video stream to set blur radius.
+
+This filter accepts the following options:
+
+@table @option
+@item min_r
+Set min allowed radius. By default is 0. Allowed range is from 0 to 254.
+@item max_r
+Set max allowed radius. By default is 8. Allowed range is from 1 to 255.
+@item planes
+@item planes
+Set which planes to process. By default all are used.
+@end table
+
 @section vectorscope
 
 Display 2 color component values in the two dimensional graph (which is called
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index da2c8b7a5e..358f121cb4 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -486,6 +486,7 @@ OBJS-$(CONFIG_UNTILE_FILTER)                 += vf_untile.o
 OBJS-$(CONFIG_USPP_FILTER)                   += vf_uspp.o qp_table.o
 OBJS-$(CONFIG_V360_FILTER)                   += vf_v360.o
 OBJS-$(CONFIG_VAGUEDENOISER_FILTER)          += vf_vaguedenoiser.o
+OBJS-$(CONFIG_VARBLUR_FILTER)                += vf_varblur.o framesync.o
 OBJS-$(CONFIG_VECTORSCOPE_FILTER)            += vf_vectorscope.o
 OBJS-$(CONFIG_VFLIP_FILTER)                  += vf_vflip.o
 OBJS-$(CONFIG_VFRDET_FILTER)                 += vf_vfrdet.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 81e1b0965b..409ab5d3c4 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -463,6 +463,7 @@ extern const AVFilter ff_vf_untile;
 extern const AVFilter ff_vf_uspp;
 extern const AVFilter ff_vf_v360;
 extern const AVFilter ff_vf_vaguedenoiser;
+extern const AVFilter ff_vf_varblur;
 extern const AVFilter ff_vf_vectorscope;
 extern const AVFilter ff_vf_vflip;
 extern const AVFilter ff_vf_vfrdet;
diff --git a/libavfilter/vf_varblur.c b/libavfilter/vf_varblur.c
new file mode 100644
index 0000000000..8ac568f55e
--- /dev/null
+++ b/libavfilter/vf_varblur.c
@@ -0,0 +1,362 @@
+/*
+ * Copyright (c) 2021 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 "libavutil/imgutils.h"
+#include "libavutil/opt.h"
+#include "libavutil/pixdesc.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "framesync.h"
+#include "internal.h"
+#include "video.h"
+
+typedef struct VarBlurContext {
+    const AVClass *class;
+    FFFrameSync fs;
+
+    int min_radius;
+    int max_radius;
+    int planes;
+
+    int depth;
+    int planewidth[4];
+    int planeheight[4];
+
+    AVFrame *sat;
+    int nb_planes;
+
+    int (*blur_plane)(AVFilterContext *s, void *arg,
+                      int jobnr, int nb_jobs);
+} VarBlurContext;
+
+#define OFFSET(x) offsetof(VarBlurContext, x)
+#define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_RUNTIME_PARAM
+
+static const AVOption varblur_options[] = {
+    { "min_r",  "set min blur radius",  OFFSET(min_radius), AV_OPT_TYPE_INT,   {.i64=0},     0, 254, FLAGS },
+    { "max_r",  "set max blur radius",  OFFSET(max_radius), AV_OPT_TYPE_INT,   {.i64=8},     1, 255, FLAGS },
+    { "planes", "set planes to filter", OFFSET(planes),     AV_OPT_TYPE_INT,   {.i64=0xF},   0, 0xF, FLAGS },
+    { NULL }
+};
+
+FRAMESYNC_DEFINE_CLASS(varblur, VarBlurContext, fs);
+
+static const enum AVPixelFormat pix_fmts[] = {
+    AV_PIX_FMT_YUVA444P, AV_PIX_FMT_YUV444P, AV_PIX_FMT_YUV440P,
+    AV_PIX_FMT_YUVJ444P, AV_PIX_FMT_YUVJ440P,
+    AV_PIX_FMT_YUVA422P, AV_PIX_FMT_YUV422P, AV_PIX_FMT_YUVA420P, AV_PIX_FMT_YUV420P,
+    AV_PIX_FMT_YUVJ422P, AV_PIX_FMT_YUVJ420P,
+    AV_PIX_FMT_YUVJ411P, AV_PIX_FMT_YUV411P, AV_PIX_FMT_YUV410P,
+    AV_PIX_FMT_YUV420P9, AV_PIX_FMT_YUV422P9, AV_PIX_FMT_YUV444P9,
+    AV_PIX_FMT_YUV420P10, AV_PIX_FMT_YUV422P10, AV_PIX_FMT_YUV444P10,
+    AV_PIX_FMT_YUV420P12, AV_PIX_FMT_YUV422P12, AV_PIX_FMT_YUV444P12, AV_PIX_FMT_YUV440P12,
+    AV_PIX_FMT_YUV420P14, AV_PIX_FMT_YUV422P14, AV_PIX_FMT_YUV444P14,
+    AV_PIX_FMT_YUV420P16, AV_PIX_FMT_YUV422P16, AV_PIX_FMT_YUV444P16,
+    AV_PIX_FMT_YUVA420P9, AV_PIX_FMT_YUVA422P9, AV_PIX_FMT_YUVA444P9,
+    AV_PIX_FMT_YUVA420P10, AV_PIX_FMT_YUVA422P10, AV_PIX_FMT_YUVA444P10,
+    AV_PIX_FMT_YUVA422P12, AV_PIX_FMT_YUVA444P12,
+    AV_PIX_FMT_YUVA420P16, AV_PIX_FMT_YUVA422P16, AV_PIX_FMT_YUVA444P16,
+    AV_PIX_FMT_GBRP, AV_PIX_FMT_GBRP9, AV_PIX_FMT_GBRP10,
+    AV_PIX_FMT_GBRP12, AV_PIX_FMT_GBRP14, AV_PIX_FMT_GBRP16,
+    AV_PIX_FMT_GBRAP, AV_PIX_FMT_GBRAP10, AV_PIX_FMT_GBRAP12, AV_PIX_FMT_GBRAP16,
+    AV_PIX_FMT_GRAY8, AV_PIX_FMT_GRAY9, AV_PIX_FMT_GRAY10, AV_PIX_FMT_GRAY12, AV_PIX_FMT_GRAY14, AV_PIX_FMT_GRAY16,
+    AV_PIX_FMT_NONE
+};
+
+#define COMPUTE_SAT(type, stype, depth)              \
+static void compute_sat##depth(const uint8_t *ssrc,  \
+                               int linesize,         \
+                               int w, int h,         \
+                               const uint8_t *dstp,  \
+                               int dst_linesize)     \
+{                                                    \
+    const type *src = (const type *)ssrc;            \
+    stype *dst = (stype *)dstp;                      \
+                                                     \
+    linesize /= (depth / 8);                         \
+    dst_linesize /= (depth / 2);                     \
+    dst += dst_linesize;                             \
+                                                     \
+    for (int y = 0; y < h; y++) {                    \
+        stype sum = 0;                               \
+                                                     \
+        for (int x = 1; x < w; x++) {                \
+            sum += src[x - 1];                       \
+            dst[x] = sum + dst[x - dst_linesize];    \
+        }                                            \
+                                                     \
+        src += linesize;                             \
+        dst += dst_linesize;                         \
+    }                                                \
+}
+
+COMPUTE_SAT(uint8_t,  uint32_t, 8)
+COMPUTE_SAT(uint16_t, uint64_t, 16)
+
+typedef struct ThreadData {
+    uint8_t *dst;
+    int dst_linesize;
+    const uint8_t *rptr;
+    int rptr_linesize;
+    int w, h;
+    const uint8_t *ptr;
+    int ptr_linesize;
+} ThreadData;
+
+static float lerpf(float v0, float v1, float f)
+{
+    return v0 + (v1 - v0) * f;
+}
+
+#define BLUR_PLANE(type, stype, bits)                          \
+static int blur_plane##bits(AVFilterContext *ctx, void *arg,   \
+                             int jobnr, int nb_jobs)           \
+{                                                              \
+    VarBlurContext *s = ctx->priv;                             \
+    const int ddepth = s->depth;                               \
+    ThreadData *td = arg;                                      \
+    const int w = td->w, h = td->h;                            \
+    const int slice_start = (h * jobnr) / nb_jobs;             \
+    const int slice_end = (h * (jobnr+1)) / nb_jobs;           \
+    const int dst_linesize = td->dst_linesize / (bits / 8);    \
+    const int ptr_linesize = td->ptr_linesize / (bits / 2);    \
+    const int rptr_linesize = td->rptr_linesize / (bits / 8);  \
+    const type *rptr = (const type *)td->rptr + slice_start * rptr_linesize; \
+    type *dst = (type *)td->dst + slice_start * dst_linesize;  \
+    const stype *ptr = (stype *)td->ptr;                       \
+    const float minr = 2.f * s->min_radius + 1.f;              \
+    const float maxr = 2.f * s->max_radius + 1.f;              \
+    const float scaler = (maxr - minr) / ((1 << ddepth) - 1);  \
+                                                               \
+    for (int y = slice_start; y < slice_end; y++) {            \
+        for (int x = 0; x < w; x++) {                          \
+            const float radiusf = minr + (FFMAX(0.f, 2 * rptr[x] + 1 - minr)) * scaler; \
+            const int radius = floorf(radiusf);                \
+            const float factor = radiusf - radius;             \
+            const int nradius = radius + 1;                    \
+            const int l = FFMIN(radius, x);                    \
+            const int r = FFMIN(radius, w - x - 1);            \
+            const int t = FFMIN(radius, y);                    \
+            const int b = FFMIN(radius, h - y - 1);            \
+            const int nl = FFMIN(nradius, x);                  \
+            const int nr = FFMIN(nradius, w - x - 1);          \
+            const int nt = FFMIN(nradius, y);                  \
+            const int nb = FFMIN(nradius, h - y - 1);          \
+            stype tl = ptr[(y - t) * ptr_linesize + x - l];    \
+            stype tr = ptr[(y - t) * ptr_linesize + x + r];    \
+            stype bl = ptr[(y + b) * ptr_linesize + x - l];    \
+            stype br = ptr[(y + b) * ptr_linesize + x + r];    \
+            stype ntl = ptr[(y - nt) * ptr_linesize + x - nl]; \
+            stype ntr = ptr[(y - nt) * ptr_linesize + x + nr]; \
+            stype nbl = ptr[(y + nb) * ptr_linesize + x - nl]; \
+            stype nbr = ptr[(y + nb) * ptr_linesize + x + nr]; \
+            stype div = (l + r) * (t + b);                     \
+            stype ndiv = (nl + nr) * (nt + nb);                \
+            stype p0 = (br + tl - bl - tr) / div;              \
+            stype n0 = (nbr + ntl - nbl - ntr) / ndiv;         \
+                                                               \
+            dst[x] = av_clip_uintp2_c(lerpf(p0, n0, factor),   \
+                                      ddepth);                 \
+        }                                                      \
+                                                               \
+        rptr += rptr_linesize;                                 \
+        dst  += dst_linesize;                                  \
+    }                                                          \
+                                                               \
+    return 0;                                                  \
+}
+
+BLUR_PLANE(uint8_t,  uint32_t, 8)
+BLUR_PLANE(uint16_t, uint64_t, 16)
+
+static int blur_frame(AVFilterContext *ctx, AVFrame *in, AVFrame *radius)
+{
+    VarBlurContext *s = ctx->priv;
+    AVFilterLink *outlink = ctx->outputs[0];
+    ThreadData td;
+    AVFrame *out;
+
+    if (av_frame_is_writable(in)) {
+        out = in;
+    } else {
+        out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
+        if (!out) {
+            av_frame_free(&in);
+            return AVERROR(ENOMEM);
+        }
+        av_frame_copy_props(out, in);
+    }
+
+    for (int plane = 0; plane < s->nb_planes; plane++) {
+        const int height = s->planeheight[plane];
+        const int width = s->planewidth[plane];
+        const int linesize = in->linesize[plane];
+        const int dst_linesize = out->linesize[plane];
+        const uint8_t *rptr = radius->data[plane];
+        const int rptr_linesize = radius->linesize[plane];
+        uint8_t *ptr = s->sat->data[plane];
+        const int ptr_linesize = s->sat->linesize[plane];
+        const uint8_t *src = in->data[plane];
+        uint8_t *dst = out->data[plane];
+
+        if (!(s->planes & (1 << plane))) {
+            if (out != in)
+                av_image_copy_plane(out->data[plane], out->linesize[plane],
+                                    in->data[plane], in->linesize[plane],
+                                    width * ((s->depth + 7) / 8), height);
+            continue;
+        }
+
+        if (s->depth <= 8)
+            compute_sat8(src, linesize, width, height, ptr, ptr_linesize);
+        else
+            compute_sat16(src, linesize, width, height, ptr, ptr_linesize);
+
+        td.dst = dst;
+        td.dst_linesize = dst_linesize;
+        td.ptr = ptr;
+        td.ptr_linesize = ptr_linesize;
+        td.rptr = rptr;
+        td.rptr_linesize = rptr_linesize;
+        td.w = width;
+        td.h = height;
+        ff_filter_execute(ctx, s->blur_plane, &td, NULL,
+                          FFMIN(height, ff_filter_get_nb_threads(ctx)));
+    }
+
+    if (out != in)
+        av_frame_free(&in);
+    return ff_filter_frame(outlink, out);
+}
+
+static int activate(AVFilterContext *ctx)
+{
+    VarBlurContext *s = ctx->priv;
+    return ff_framesync_activate(&s->fs);
+}
+
+static int varblur_frame(FFFrameSync *fs)
+{
+    AVFilterContext *ctx = fs->parent;
+    VarBlurContext *s = ctx->priv;
+    AVFrame *in, *radius;
+    int ret;
+
+    if (s->max_radius <= s->min_radius)
+        s->max_radius = s->min_radius + 1;
+
+    ret = ff_framesync_dualinput_get(fs, &in, &radius);
+    if (ret < 0)
+        return ret;
+    if (!radius)
+        return ff_filter_frame(ctx->outputs[0], in);
+    return blur_frame(ctx, in, radius);
+}
+
+static int config_output(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    AVFilterLink *inlink = ctx->inputs[0];
+    AVFilterLink *radiuslink = ctx->inputs[1];
+    VarBlurContext *s = ctx->priv;
+    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(outlink->format);
+    int ret;
+
+    if (inlink->w != radiuslink->w || inlink->h != radiuslink->h) {
+        av_log(ctx, AV_LOG_ERROR, "First input link %s parameters "
+               "(size %dx%d) do not match the corresponding "
+               "second input link %s parameters (size %dx%d)\n",
+               ctx->input_pads[0].name, inlink->w, inlink->h,
+               ctx->input_pads[1].name, radiuslink->w, radiuslink->h);
+        return AVERROR(EINVAL);
+    }
+
+    outlink->w = inlink->w;
+    outlink->h = inlink->h;
+    outlink->time_base = inlink->time_base;
+    outlink->sample_aspect_ratio = inlink->sample_aspect_ratio;
+    outlink->frame_rate = inlink->frame_rate;
+
+    s->depth = desc->comp[0].depth;
+    s->blur_plane = s->depth <= 8 ? blur_plane8 : blur_plane16;
+
+    s->planewidth[1]  = s->planewidth[2]  = AV_CEIL_RSHIFT(outlink->w, desc->log2_chroma_w);
+    s->planewidth[0]  = s->planewidth[3]  = outlink->w;
+    s->planeheight[1] = s->planeheight[2] = AV_CEIL_RSHIFT(outlink->h, desc->log2_chroma_h);
+    s->planeheight[0] = s->planeheight[3] = outlink->h;
+
+    s->nb_planes = av_pix_fmt_count_planes(outlink->format);
+
+    s->sat = ff_get_video_buffer(outlink, (outlink->w + 1) * 4 * ((s->depth + 7) / 8), outlink->h + 1);
+    if (!s->sat)
+        return AVERROR(ENOMEM);
+
+    s->fs.on_event = varblur_frame;
+    if ((ret = ff_framesync_init_dualinput(&s->fs, ctx)) < 0)
+        return ret;
+
+    ret = ff_framesync_configure(&s->fs);
+    outlink->time_base = s->fs.time_base;
+
+    return ret;
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    VarBlurContext *s = ctx->priv;
+
+    ff_framesync_uninit(&s->fs);
+    av_frame_free(&s->sat);
+}
+
+static const AVFilterPad varblur_inputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+    },
+    {
+        .name = "radius",
+        .type = AVMEDIA_TYPE_VIDEO,
+    },
+};
+
+static const AVFilterPad varblur_outputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .config_props = config_output,
+    },
+};
+
+const AVFilter ff_vf_varblur = {
+    .name          = "varblur",
+    .description   = NULL_IF_CONFIG_SMALL("Apply Variable Blur filter."),
+    .priv_size     = sizeof(VarBlurContext),
+    .priv_class    = &varblur_class,
+    .activate      = activate,
+    .preinit       = varblur_framesync_preinit,
+    .uninit        = uninit,
+    FILTER_INPUTS(varblur_inputs),
+    FILTER_OUTPUTS(varblur_outputs),
+    FILTER_PIXFMTS_ARRAY(pix_fmts),
+    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE_INTERNAL |
+                     AVFILTER_FLAG_SLICE_THREADS,
+    .process_command = ff_filter_process_command,
+};
