diff --git a/doc/filters.texi b/doc/filters.texi
index 9dfe95f40d..325753c8f4 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -5817,6 +5817,40 @@ Convert M/S signal to L/R:
 @end example
 @end itemize
 
+@section stereoupmix
+Upmix stereo audio.
+
+This filter upmixes stereo audio using adaptive panning method.
+
+The filter accepts the following options:
+
+@table @option
+@item upmix
+Set the upmix mode. Can be one of the following:
+@table @samp
+@item 2.1
+@item 3.0
+@item 3.1
+@item 4.0
+@item 4.1
+@item 5.0
+@item 5.1
+@end table
+Default value is @var{5.1}.
+
+@item center
+Set the center audio strength. Allowed range is from 0.0 to 1.0.
+Default value is 0.5.
+
+@item ambience
+Set the ambience audio strength. Allowed range is from 0.0 to 1.0.
+Default value is 0.5.
+@end table
+
+@subsection Commands
+
+This filter supports the all above options except @code{upmix} as @ref{commands}.
+
 @section stereowiden
 
 This filter enhance the stereo effect by suppressing signal common to both
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 1af85a71a0..a9d76a1eaf 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -145,6 +145,7 @@ OBJS-$(CONFIG_SILENCEREMOVE_FILTER)          += af_silenceremove.o
 OBJS-$(CONFIG_SOFALIZER_FILTER)              += af_sofalizer.o
 OBJS-$(CONFIG_SPEECHNORM_FILTER)             += af_speechnorm.o
 OBJS-$(CONFIG_STEREOTOOLS_FILTER)            += af_stereotools.o
+OBJS-$(CONFIG_STEREOUPMIX_FILTER)            += af_stereoupmix.o
 OBJS-$(CONFIG_STEREOWIDEN_FILTER)            += af_stereowiden.o
 OBJS-$(CONFIG_SUPEREQUALIZER_FILTER)         += af_superequalizer.o
 OBJS-$(CONFIG_SURROUND_FILTER)               += af_surround.o
diff --git a/libavfilter/af_stereoupmix.c b/libavfilter/af_stereoupmix.c
new file mode 100644
index 0000000000..813f21b088
--- /dev/null
+++ b/libavfilter/af_stereoupmix.c
@@ -0,0 +1,352 @@
+/*
+ * Copyright (c) 2020 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/avassert.h"
+#include "libavutil/channel_layout.h"
+#include "libavutil/opt.h"
+#include "avfilter.h"
+#include "audio.h"
+#include "formats.h"
+
+enum UpmixMode {
+    UPMIX_2_1,
+    UPMIX_3_0,
+    UPMIX_3_1,
+    UPMIX_4_0,
+    UPMIX_4_1,
+    UPMIX_5_0,
+    UPMIX_5_1,
+    NB_UPMIX
+};
+
+typedef struct StereoUpmixContext {
+    const AVClass *class;
+
+    int upmix;
+    float center;
+    float ambience;
+
+    uint64_t out_layout;
+
+    float fl, fr;
+    float y;
+    float pk;
+    float wl, wr;
+
+    float a[2];
+    float b[3];
+    float z[2];
+} StereoUpmixContext;
+
+#define OFFSET(x) offsetof(StereoUpmixContext, x)
+#define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
+#define TFLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_RUNTIME_PARAM
+
+static const AVOption stereoupmix_options[] = {
+    { "upmix",  "set upmix mode",      OFFSET(upmix),  AV_OPT_TYPE_INT,   {.i64=UPMIX_5_1}, 0, NB_UPMIX-1, FLAGS, "upmix" },
+    { "2.1",    NULL,                  0,              AV_OPT_TYPE_CONST, {.i64=UPMIX_2_1}, 0,          0, FLAGS, "upmix" },
+    { "3.0",    NULL,                  0,              AV_OPT_TYPE_CONST, {.i64=UPMIX_3_0}, 0,          0, FLAGS, "upmix" },
+    { "3.1",    NULL,                  0,              AV_OPT_TYPE_CONST, {.i64=UPMIX_3_1}, 0,          0, FLAGS, "upmix" },
+    { "4.0",    NULL,                  0,              AV_OPT_TYPE_CONST, {.i64=UPMIX_4_0}, 0,          0, FLAGS, "upmix" },
+    { "4.1",    NULL,                  0,              AV_OPT_TYPE_CONST, {.i64=UPMIX_4_1}, 0,          0, FLAGS, "upmix" },
+    { "5.0",    NULL,                  0,              AV_OPT_TYPE_CONST, {.i64=UPMIX_5_0}, 0,          0, FLAGS, "upmix" },
+    { "5.1",    NULL,                  0,              AV_OPT_TYPE_CONST, {.i64=UPMIX_5_1}, 0,          0, FLAGS, "upmix" },
+    { "center", "set center strength", OFFSET(center), AV_OPT_TYPE_FLOAT, {.dbl=0.5},       0,          1, TFLAGS },
+    { "ambience", "set ambience strength", OFFSET(ambience), AV_OPT_TYPE_FLOAT, {.dbl=0.5}, 0,          1, TFLAGS },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(stereoupmix);
+
+static av_cold int init(AVFilterContext *ctx)
+{
+    StereoUpmixContext *s = ctx->priv;
+
+    s->wl = s->wr = M_SQRT1_2;
+
+    switch (s->upmix) {
+    case UPMIX_2_1:
+        s->out_layout = AV_CH_LAYOUT_2POINT1;
+        break;
+    case UPMIX_3_0:
+        s->out_layout = AV_CH_LAYOUT_SURROUND;
+        break;
+    case UPMIX_3_1:
+        s->out_layout = AV_CH_LAYOUT_3POINT1;
+        break;
+    case UPMIX_4_0:
+        s->out_layout = AV_CH_LAYOUT_4POINT0;
+        break;
+    case UPMIX_4_1:
+        s->out_layout = AV_CH_LAYOUT_4POINT1;
+        break;
+    case UPMIX_5_0:
+        s->out_layout = AV_CH_LAYOUT_5POINT0_BACK;
+        break;
+    case UPMIX_5_1:
+        s->out_layout = AV_CH_LAYOUT_5POINT1_BACK;
+        break;
+    default:
+        av_assert0(0);
+    }
+
+    return 0;
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+    StereoUpmixContext *s = ctx->priv;
+    AVFilterFormats *formats = NULL;
+    AVFilterChannelLayouts *layouts = NULL;
+    int ret;
+
+    ret = ff_add_format(&formats, AV_SAMPLE_FMT_FLT);
+    if (ret)
+        return ret;
+    ret = ff_set_common_formats(ctx, formats);
+    if (ret)
+        return ret;
+
+    layouts = NULL;
+    ret = ff_add_channel_layout(&layouts, s->out_layout);
+    if (ret)
+        return ret;
+
+    ret = ff_channel_layouts_ref(layouts, &ctx->outputs[0]->incfg.channel_layouts);
+    if (ret)
+        return ret;
+
+    layouts = NULL;
+    ret = ff_add_channel_layout(&layouts, AV_CH_LAYOUT_STEREO);
+    if (ret)
+        return ret;
+
+    ret = ff_channel_layouts_ref(layouts, &ctx->inputs[0]->outcfg.channel_layouts);
+    if (ret)
+        return ret;
+
+    formats = ff_all_samplerates();
+    if (!formats)
+        return AVERROR(ENOMEM);
+    return ff_set_common_samplerates(ctx, formats);
+}
+
+static void upmix(AVFilterContext *ctx, AVFrame *out, AVFrame *in)
+{
+    StereoUpmixContext *s = ctx->priv;
+    const float center = s->center;
+    const float ambience = s->ambience;
+    const float *src = (const float *)in->data[0];
+    const float b0 = s->b[0];
+    const float b1 = s->b[1];
+    const float b2 = s->b[2];
+    const float a1 = s->a[0];
+    const float a2 = s->a[1];
+    float *dst = (float *)out->data[0];
+    float wl = s->wl, wr = s->wr;
+    float fl = s->fl, fr = s->fr;
+    float pk = s->pk;
+    float y = s->y;
+    float z0 = s->z[0];
+    float z1 = s->z[1];
+
+    for (int n = 0; n < in->nb_samples; n++) {
+        float nwl, nwr;
+        float clr, cl, cr;
+        float slr, sl, sr;
+        float beta, gamma, q;
+        float ro = 0.001f;
+        float sing, cosb, sinb;
+        float FL, FR, FC, LFE, SL, SR, SC;
+        float mid, side;
+        float g, ig2, gg;
+
+        nwl = wl + ro * y * (fl - wl * y);
+        nwr = wr + ro * y * (fr - wr * y);
+        fl = src[n * 2    ];
+        fr = src[n * 2 + 1];
+        y = nwl * fl + nwr * fr;
+        q = nwr * fl - nwl * fr;
+        pk = pk + ro * (2.f * fl * fr - (fl * fl + fr * fr) * pk);
+        av_assert0(pk >= -1.f && pk <= 1.f);
+        beta = asinf(1.f - fmaxf(pk, 0.f));
+        gamma = acosf(1.f + fminf(pk, 0.f));
+        cosb = cosf(beta);
+        sinb = sinf(beta);
+        sing = sinf(gamma);
+        g = cosb * cosb;
+        gg = sinb * sinb;
+        ig2 = (1.f - g) * (1.f - g);
+
+        clr = (nwr * nwr - nwl * nwl) * cosb;
+        slr = (nwr * nwr - nwl * nwl) * sing;
+        cl = clr  < 0 ? -clr : 0.f;
+        cr = clr >= 0 ?  clr : 0.f;
+        sl = slr  < 0 ? -slr : 0.f;
+        sr = slr >= 0 ?  slr : 0.f;
+        mid = 0.5f * (fl + fr);
+        side = 0.5f * (fr - fl);
+        FC = cosb * nwl * nwr * y + gg * mid * center;
+        FL = cl * y + g * nwl * q + ig2 * fl;
+        FR = cr * y + g * nwr * q + ig2 * fr;
+        SC = sinb * q;
+        SL = SC + sl * side * ambience;
+        SR = SC + sr * side * ambience;
+        LFE = FC * b0 + z0;
+        z0 = b1 * FC + z1 + a1 * LFE;
+        z1 = b2 * FC + a2 * LFE;
+
+        switch (s->upmix) {
+        case UPMIX_2_1:
+            dst[n * 3 + 0] = fl;
+            dst[n * 3 + 1] = fr;
+            dst[n * 3 + 2] = LFE;
+            break;
+        case UPMIX_3_0:
+            dst[n * 3 + 0] = fl;
+            dst[n * 3 + 1] = fr;
+            dst[n * 3 + 2] = FC;
+            break;
+        case UPMIX_3_1:
+            dst[n * 4 + 0] = fl;
+            dst[n * 4 + 1] = fr;
+            dst[n * 4 + 2] = FC;
+            dst[n * 4 + 3] = LFE;
+            break;
+        case UPMIX_4_0:
+            dst[n * 4 + 0] = FL;
+            dst[n * 4 + 1] = FR;
+            dst[n * 4 + 2] = FC;
+            dst[n * 4 + 3] = SC;
+            break;
+        case UPMIX_4_1:
+            dst[n * 5 + 0] = FL;
+            dst[n * 5 + 1] = FR;
+            dst[n * 5 + 2] = FC;
+            dst[n * 5 + 3] = LFE;
+            dst[n * 5 + 4] = SC;
+            break;
+        case UPMIX_5_0:
+            dst[n * 5 + 0] = FL;
+            dst[n * 5 + 1] = FR;
+            dst[n * 5 + 2] = FC;
+            dst[n * 5 + 3] = SL;
+            dst[n * 5 + 4] = SR;
+            break;
+        case UPMIX_5_1:
+            dst[n * 6 + 0] = FL;
+            dst[n * 6 + 1] = FR;
+            dst[n * 6 + 2] = FC;
+            dst[n * 6 + 3] = LFE;
+            dst[n * 6 + 4] = SL;
+            dst[n * 6 + 5] = SR;
+            break;
+        default:
+            av_assert0(0);
+        }
+
+        wl = nwl;
+        wr = nwr;
+    }
+
+    s->pk = pk;
+    s->y = y;
+
+    s->fl = fl;
+    s->fr = fr;
+
+    s->wl = wl;
+    s->wr = wr;
+
+    s->z[0] = z0;
+    s->z[1] = z1;
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+    AVFilterContext *ctx = inlink->dst;
+    AVFilterLink *outlink = ctx->outputs[0];
+    AVFrame *out;
+
+    out = ff_get_audio_buffer(outlink, in->nb_samples);
+    if (!out) {
+        av_frame_free(&in);
+        return AVERROR(ENOMEM);
+    }
+    av_frame_copy_props(out, in);
+
+    upmix(ctx, out, in);
+
+    av_frame_free(&in);
+    return ff_filter_frame(outlink, out);
+}
+
+static int config_output(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    StereoUpmixContext *s = ctx->priv;
+    double w0 = 2. * M_PI * 120. / outlink->sample_rate;
+    double alpha = sin(w0) / 2. * sqrt(2.);
+    double a0 = 1. + alpha;
+
+    s->a[0] = 2. * cos(w0);
+    s->a[1] = alpha - 1.;
+    s->b[0] = (1. - cos(w0)) / 2.;
+    s->b[1] =  1. - cos(w0);
+    s->b[2] = (1. - cos(w0)) / 2.;
+
+    s->a[0] /= a0;
+    s->a[1] /= a0;
+    s->b[0] /= a0;
+    s->b[1] /= a0;
+    s->b[2] /= a0;
+
+    return 0;
+}
+
+static const AVFilterPad inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_AUDIO,
+        .filter_frame = filter_frame,
+    },
+    { NULL }
+};
+
+static const AVFilterPad outputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_AUDIO,
+        .config_props = config_output,
+    },
+    { NULL }
+};
+
+AVFilter ff_af_stereoupmix = {
+    .name            = "stereoupmix",
+    .description     = NULL_IF_CONFIG_SMALL("Upmix stereo audio."),
+    .query_formats   = query_formats,
+    .priv_size       = sizeof(StereoUpmixContext),
+    .priv_class      = &stereoupmix_class,
+    .init            = init,
+    .inputs          = inputs,
+    .outputs         = outputs,
+    .process_command = ff_filter_process_command,
+};
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 16e1f08a29..bb96ca88ab 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -139,6 +139,7 @@ extern AVFilter ff_af_silenceremove;
 extern AVFilter ff_af_sofalizer;
 extern AVFilter ff_af_speechnorm;
 extern AVFilter ff_af_stereotools;
+extern AVFilter ff_af_stereoupmix;
 extern AVFilter ff_af_stereowiden;
 extern AVFilter ff_af_superequalizer;
 extern AVFilter ff_af_surround;
