diff --git a/doc/filters.texi b/doc/filters.texi
index 426cb158da..38698b6542 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -13382,6 +13382,28 @@ By default value is 0.
 
 The @code{hysteresis} filter also supports the @ref{framesync} options.
 
+@section identity
+
+Obtain the identity score between two input videos.
+
+This filter takes two input videos.
+
+Both input videos must have the same resolution and pixel format for
+this filter to work correctly. Also it assumes that both inputs
+have the same number of frames, which are compared one by one.
+
+The obtained per component, average, min and max identity score is printed through
+the logging system.
+
+The filter stores the calculated identity scores of each frame in frame metadata.
+
+In the below example the input file @file{main.mpg} being processed is compared
+with the reference file @file{ref.mpg}.
+
+@example
+ffmpeg -i main.mpg -i ref.mpg -lavfi identity -f null -
+@end example
+
 @section idet
 
 Detect video interlacing type.
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index fba103ff80..346ed6f15c 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -299,6 +299,7 @@ OBJS-$(CONFIG_HWMAP_FILTER)                  += vf_hwmap.o
 OBJS-$(CONFIG_HWUPLOAD_CUDA_FILTER)          += vf_hwupload_cuda.o
 OBJS-$(CONFIG_HWUPLOAD_FILTER)               += vf_hwupload.o
 OBJS-$(CONFIG_HYSTERESIS_FILTER)             += vf_hysteresis.o framesync.o
+OBJS-$(CONFIG_IDENTITY_FILTER)               += vf_identity.o
 OBJS-$(CONFIG_IDET_FILTER)                   += vf_idet.o
 OBJS-$(CONFIG_IL_FILTER)                     += vf_il.o
 OBJS-$(CONFIG_INFLATE_FILTER)                += vf_neighbor.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index d2d543f917..4bd8eabd28 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -283,6 +283,7 @@ extern AVFilter ff_vf_hwmap;
 extern AVFilter ff_vf_hwupload;
 extern AVFilter ff_vf_hwupload_cuda;
 extern AVFilter ff_vf_hysteresis;
+extern AVFilter ff_vf_identity;
 extern AVFilter ff_vf_idet;
 extern AVFilter ff_vf_il;
 extern AVFilter ff_vf_inflate;
diff --git a/libavfilter/vf_identity.c b/libavfilter/vf_identity.c
new file mode 100644
index 0000000000..02dda392b3
--- /dev/null
+++ b/libavfilter/vf_identity.c
@@ -0,0 +1,372 @@
+/*
+ * 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
+ */
+
+/**
+ * @file
+ * Caculate the Identity between two input videos.
+ */
+
+#include "libavutil/avstring.h"
+#include "libavutil/opt.h"
+#include "libavutil/pixdesc.h"
+#include "avfilter.h"
+#include "drawutils.h"
+#include "formats.h"
+#include "framesync.h"
+#include "internal.h"
+#include "video.h"
+
+typedef struct IdentityContext {
+    const AVClass *class;
+    FFFrameSync fs;
+    double score, min_score, max_score, score_comp[4];
+    uint64_t nb_frames;
+    int is_rgb;
+    uint8_t rgba_map[4];
+    char comps[4];
+    int nb_components;
+    int nb_threads;
+    int planewidth[4];
+    int planeheight[4];
+    uint64_t **scores;
+    unsigned (*filter_line)(const uint8_t *buf, const uint8_t *ref, int w);
+} IdentityContext;
+
+#define OFFSET(x) offsetof(IdentityContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+
+static const AVOption identity_options[] = {
+    { NULL }
+};
+
+FRAMESYNC_DEFINE_CLASS(identity, IdentityContext, fs);
+
+static unsigned identity_line_8bit(const uint8_t *main_line,  const uint8_t *ref_line, int outw)
+{
+    unsigned score = 0;
+
+    for (int j = 0; j < outw; j++)
+        score += main_line[j] == ref_line[j];
+
+    return score;
+}
+
+static unsigned identity_line_16bit(const uint8_t *mmain_line, const uint8_t *rref_line, int outw)
+{
+    const uint16_t *main_line = (const uint16_t *)mmain_line;
+    const uint16_t *ref_line = (const uint16_t *)rref_line;
+    unsigned score = 0;
+
+    for (int j = 0; j < outw; j++)
+        score += main_line[j] == ref_line[j];
+
+    return score;
+}
+
+typedef struct ThreadData {
+    const uint8_t *main_data[4];
+    const uint8_t *ref_data[4];
+    int main_linesize[4];
+    int ref_linesize[4];
+    int planewidth[4];
+    int planeheight[4];
+    uint64_t **score;
+    int nb_components;
+} ThreadData;
+
+static
+int compute_images_identity(AVFilterContext *ctx, void *arg,
+                            int jobnr, int nb_jobs)
+{
+    IdentityContext *s = ctx->priv;
+    ThreadData *td = arg;
+    uint64_t *score = td->score[jobnr];
+
+    for (int c = 0; c < td->nb_components; c++) {
+        const int outw = td->planewidth[c];
+        const int outh = td->planeheight[c];
+        const int slice_start = (outh * jobnr) / nb_jobs;
+        const int slice_end = (outh * (jobnr+1)) / nb_jobs;
+        const int ref_linesize = td->ref_linesize[c];
+        const int main_linesize = td->main_linesize[c];
+        const uint8_t *main_line = td->main_data[c] + main_linesize * slice_start;
+        const uint8_t *ref_line = td->ref_data[c] + ref_linesize * slice_start;
+        uint64_t m = 0;
+
+        for (int i = slice_start; i < slice_end; i++) {
+            m += s->filter_line(main_line, ref_line, outw);
+            ref_line += ref_linesize;
+            main_line += main_linesize;
+        }
+        score[c] = m;
+    }
+
+    return 0;
+}
+
+static void set_meta(AVDictionary **metadata, const char *key, char comp, float d)
+{
+    char value[128];
+    snprintf(value, sizeof(value), "%f", d);
+    if (comp) {
+        char key2[128];
+        snprintf(key2, sizeof(key2), "%s%c", key, comp);
+        av_dict_set(metadata, key2, value, 0);
+    } else {
+        av_dict_set(metadata, key, value, 0);
+    }
+}
+
+static int do_identity(FFFrameSync *fs)
+{
+    AVFilterContext *ctx = fs->parent;
+    IdentityContext *s = ctx->priv;
+    AVFrame *master, *ref;
+    double comp_identity[4], score = 0.;
+    uint64_t comp_sum[4] = { 0 };
+    AVDictionary **metadata;
+    ThreadData td;
+    int ret;
+
+    ret = ff_framesync_dualinput_get(fs, &master, &ref);
+    if (ret < 0)
+        return ret;
+    if (ctx->is_disabled || !ref)
+        return ff_filter_frame(ctx->outputs[0], master);
+    metadata = &master->metadata;
+
+    td.nb_components = s->nb_components;
+    td.score = s->scores;
+    for (int c = 0; c < s->nb_components; c++) {
+        td.main_data[c] = master->data[c];
+        td.ref_data[c] = ref->data[c];
+        td.main_linesize[c] = master->linesize[c];
+        td.ref_linesize[c] = ref->linesize[c];
+        td.planewidth[c] = s->planewidth[c];
+        td.planeheight[c] = s->planeheight[c];
+    }
+
+    ctx->internal->execute(ctx, compute_images_identity, &td, NULL, FFMIN(s->planeheight[1], s->nb_threads));
+
+    for (int j = 0; j < s->nb_threads; j++) {
+        for (int c = 0; c < s->nb_components; c++)
+            comp_sum[c] += s->scores[j][c];
+    }
+
+    for (int c = 0; c < s->nb_components; c++)
+        comp_identity[c] = comp_sum[c] / ((double)s->planewidth[c] * s->planeheight[c]);
+
+    for (int c = 0; c < s->nb_components; c++)
+        score += comp_identity[c];
+    score /= s->nb_components;
+
+    s->min_score = FFMIN(s->min_score, score);
+    s->max_score = FFMAX(s->max_score, score);
+
+    s->score += score;
+
+    for (int j = 0; j < s->nb_components; j++)
+        s->score_comp[j] += comp_identity[j];
+    s->nb_frames++;
+
+    for (int j = 0; j < s->nb_components; j++) {
+        int c = s->is_rgb ? s->rgba_map[j] : j;
+        set_meta(metadata, "lavfi.identity.identity.", s->comps[j], comp_identity[c]);
+    }
+    set_meta(metadata, "lavfi.identity.identity_avg", 0, score);
+
+    return ff_filter_frame(ctx->outputs[0], master);
+}
+
+static av_cold int init(AVFilterContext *ctx)
+{
+    IdentityContext *s = ctx->priv;
+
+    s->fs.on_event = do_identity;
+
+    return 0;
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+    static const enum AVPixelFormat pix_fmts[] = {
+        AV_PIX_FMT_GRAY8, AV_PIX_FMT_GRAY9, AV_PIX_FMT_GRAY10, AV_PIX_FMT_GRAY12, AV_PIX_FMT_GRAY14, AV_PIX_FMT_GRAY16,
+#define PF_NOALPHA(suf) AV_PIX_FMT_YUV420##suf,  AV_PIX_FMT_YUV422##suf,  AV_PIX_FMT_YUV444##suf
+#define PF_ALPHA(suf)   AV_PIX_FMT_YUVA420##suf, AV_PIX_FMT_YUVA422##suf, AV_PIX_FMT_YUVA444##suf
+#define PF(suf)         PF_NOALPHA(suf), PF_ALPHA(suf)
+        PF(P), PF(P9), PF(P10), PF_NOALPHA(P12), PF_NOALPHA(P14), PF(P16),
+        AV_PIX_FMT_YUV440P, AV_PIX_FMT_YUV411P, AV_PIX_FMT_YUV410P,
+        AV_PIX_FMT_YUVJ411P, AV_PIX_FMT_YUVJ420P, AV_PIX_FMT_YUVJ422P,
+        AV_PIX_FMT_YUVJ440P, AV_PIX_FMT_YUVJ444P,
+        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_NONE
+    };
+
+    AVFilterFormats *fmts_list = ff_make_format_list(pix_fmts);
+    if (!fmts_list)
+        return AVERROR(ENOMEM);
+    return ff_set_common_formats(ctx, fmts_list);
+}
+
+static int config_input_ref(AVFilterLink *inlink)
+{
+    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
+    AVFilterContext *ctx  = inlink->dst;
+    IdentityContext *s = ctx->priv;
+
+    s->nb_threads = ff_filter_get_nb_threads(ctx);
+    s->nb_components = desc->nb_components;
+    if (ctx->inputs[0]->w != ctx->inputs[1]->w ||
+        ctx->inputs[0]->h != ctx->inputs[1]->h) {
+        av_log(ctx, AV_LOG_ERROR, "Width and height of input videos must be same.\n");
+        return AVERROR(EINVAL);
+    }
+    if (ctx->inputs[0]->format != ctx->inputs[1]->format) {
+        av_log(ctx, AV_LOG_ERROR, "Inputs must be of same pixel format.\n");
+        return AVERROR(EINVAL);
+    }
+
+    s->is_rgb = ff_fill_rgba_map(s->rgba_map, inlink->format) >= 0;
+    s->comps[0] = s->is_rgb ? 'R' : 'Y' ;
+    s->comps[1] = s->is_rgb ? 'G' : 'U' ;
+    s->comps[2] = s->is_rgb ? 'B' : 'V' ;
+    s->comps[3] = 'A';
+
+    s->planeheight[1] = s->planeheight[2] = AV_CEIL_RSHIFT(inlink->h, desc->log2_chroma_h);
+    s->planeheight[0] = s->planeheight[3] = inlink->h;
+    s->planewidth[1]  = s->planewidth[2]  = AV_CEIL_RSHIFT(inlink->w, desc->log2_chroma_w);
+    s->planewidth[0]  = s->planewidth[3]  = inlink->w;
+
+    s->scores = av_calloc(s->nb_threads, sizeof(*s->scores));
+    if (!s->scores)
+        return AVERROR(ENOMEM);
+
+    for (int t = 0; t < s->nb_threads && s->scores; t++) {
+        s->scores[t] = av_calloc(s->nb_components, sizeof(*s->scores[0]));
+        if (!s->scores[t])
+            return AVERROR(ENOMEM);
+    }
+
+    s->min_score = +INFINITY;
+    s->max_score = -INFINITY;
+
+    s->filter_line = desc->comp[0].depth > 8 ? identity_line_16bit : identity_line_8bit;
+
+    return 0;
+}
+
+static int config_output(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    IdentityContext *s = ctx->priv;
+    AVFilterLink *mainlink = ctx->inputs[0];
+    int ret;
+
+    ret = ff_framesync_init_dualinput(&s->fs, ctx);
+    if (ret < 0)
+        return ret;
+    outlink->w = mainlink->w;
+    outlink->h = mainlink->h;
+    outlink->time_base = mainlink->time_base;
+    outlink->sample_aspect_ratio = mainlink->sample_aspect_ratio;
+    outlink->frame_rate = mainlink->frame_rate;
+    if ((ret = ff_framesync_configure(&s->fs)) < 0)
+        return ret;
+
+    outlink->time_base = s->fs.time_base;
+
+    if (av_cmp_q(mainlink->time_base, outlink->time_base) ||
+        av_cmp_q(ctx->inputs[1]->time_base, outlink->time_base))
+        av_log(ctx, AV_LOG_WARNING, "not matching timebases found between first input: %d/%d and second input %d/%d, results may be incorrect!\n",
+               mainlink->time_base.num, mainlink->time_base.den,
+               ctx->inputs[1]->time_base.num, ctx->inputs[1]->time_base.den);
+
+    return 0;
+}
+
+static int activate(AVFilterContext *ctx)
+{
+    IdentityContext *s = ctx->priv;
+    return ff_framesync_activate(&s->fs);
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    IdentityContext *s = ctx->priv;
+
+    if (s->nb_frames > 0) {
+        char buf[256];
+
+        buf[0] = 0;
+        for (int j = 0; j < s->nb_components; j++) {
+            int c = s->is_rgb ? s->rgba_map[j] : j;
+            av_strlcatf(buf, sizeof(buf), " %c:%f", s->comps[j], s->score_comp[c] / s->nb_frames);
+        }
+
+        av_log(ctx, AV_LOG_INFO, "Identity%s average:%f min:%f max:%f\n",
+               buf,
+               s->score / s->nb_frames,
+               s->min_score,
+               s->max_score);
+    }
+
+    ff_framesync_uninit(&s->fs);
+    for (int t = 0; t < s->nb_threads && s->scores; t++)
+        av_freep(&s->scores[t]);
+    av_freep(&s->scores);
+}
+
+static const AVFilterPad identity_inputs[] = {
+    {
+        .name         = "main",
+        .type         = AVMEDIA_TYPE_VIDEO,
+    },{
+        .name         = "reference",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .config_props = config_input_ref,
+    },
+    { NULL }
+};
+
+static const AVFilterPad identity_outputs[] = {
+    {
+        .name          = "default",
+        .type          = AVMEDIA_TYPE_VIDEO,
+        .config_props  = config_output,
+    },
+    { NULL }
+};
+
+AVFilter ff_vf_identity = {
+    .name          = "identity",
+    .description   = NULL_IF_CONFIG_SMALL("Calculate the Identity between two video streams."),
+    .preinit       = identity_framesync_preinit,
+    .init          = init,
+    .uninit        = uninit,
+    .query_formats = query_formats,
+    .activate      = activate,
+    .priv_size     = sizeof(IdentityContext),
+    .priv_class    = &identity_class,
+    .inputs        = identity_inputs,
+    .outputs       = identity_outputs,
+    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE_INTERNAL | AVFILTER_FLAG_SLICE_THREADS,
+};
