lavfi: add nlmeans filter

Fixes Ticket #4910

5 files changed, 647 insertions, 2 deletions

diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 5cd10faabb..57a38d3754 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -220,6 +220,7 @@ OBJS-$(CONFIG_METADATA_FILTER)               += f_metadata.o
 OBJS-$(CONFIG_MINTERPOLATE_FILTER)           += vf_minterpolate.o motion_estimation.o
 OBJS-$(CONFIG_MPDECIMATE_FILTER)             += vf_mpdecimate.o
 OBJS-$(CONFIG_NEGATE_FILTER)                 += vf_lut.o
+OBJS-$(CONFIG_NLMEANS_FILTER)                += vf_nlmeans.o
 OBJS-$(CONFIG_NNEDI_FILTER)                  += vf_nnedi.o
 OBJS-$(CONFIG_NOFORMAT_FILTER)               += vf_format.o
 OBJS-$(CONFIG_NOISE_FILTER)                  += vf_noise.o
@@ -354,7 +355,7 @@ SKIPHEADERS-$(CONFIG_OPENCL)                 += opencl_internal.h deshake_opencl
 OBJS-$(CONFIG_SHARED)                        += log2_tab.o
 
 TOOLS     = graph2dot
-TESTPROGS = drawutils filtfmts formats
+TESTPROGS = drawutils filtfmts formats integral
 
 TOOLS-$(CONFIG_LIBZMQ) += zmqsend
 
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 47d95f5f6a..8f542fddb6 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -237,6 +237,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER(MINTERPOLATE,   minterpolate,   vf);
     REGISTER_FILTER(MPDECIMATE,     mpdecimate,     vf);
     REGISTER_FILTER(NEGATE,         negate,         vf);
+    REGISTER_FILTER(NLMEANS,        nlmeans,        vf);
     REGISTER_FILTER(NNEDI,          nnedi,          vf);
     REGISTER_FILTER(NOFORMAT,       noformat,       vf);
     REGISTER_FILTER(NOISE,          noise,          vf);
diff --git a/libavfilter/tests/integral.c b/libavfilter/tests/integral.c
new file mode 100644
index 0000000000..8a2286b54d
--- /dev/null
+++ b/libavfilter/tests/integral.c
@@ -0,0 +1,92 @@
+/*
+ * 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 "libavfilter/vf_nlmeans.c"
+
+static void display_integral(const uint32_t *ii, int w, int h, int lz_32)
+{
+    int x, y;
+
+    for (y = 0; y < h; y++) {
+        for (x = 0; x < w; x++)
+            printf(" %7x", ii[y*lz_32 + x]);
+        printf("\n");
+    }
+    printf("---------------\n");
+}
+
+int main(void)
+{
+    int ret = 0, xoff, yoff;
+
+    // arbitrary test source of size 6x4 and linesize=8
+    const int w = 6, h = 5, lz = 8;
+    static const uint8_t src[] = {
+        0xb0, 0x71, 0xfb, 0xd8, 0x01, 0xd9, /***/ 0x01, 0x02,
+        0x51, 0x8e, 0x41, 0x0f, 0x84, 0x58, /***/ 0x03, 0x04,
+        0xc7, 0x8d, 0x07, 0x70, 0x5c, 0x47, /***/ 0x05, 0x06,
+        0x09, 0x4e, 0xfc, 0x74, 0x8f, 0x9a, /***/ 0x07, 0x08,
+        0x60, 0x8e, 0x20, 0xaa, 0x95, 0x7d, /***/ 0x09, 0x0a,
+    };
+
+    const int e = 3;
+    const int ii_w = w+e*2, ii_h = h+e*2;
+
+    // align to 4 the linesize, "+1" is for the space of the left 0-column
+    const int ii_lz_32 = ((ii_w + 1) + 3) & ~3;
+
+    // "+1" is for the space of the top 0-line
+    uint32_t *ii  = av_mallocz_array(ii_h + 1, ii_lz_32 * sizeof(*ii));
+    uint32_t *ii2 = av_mallocz_array(ii_h + 1, ii_lz_32 * sizeof(*ii2));
+
+    uint32_t *ii_start  = ii  + ii_lz_32 + 1; // skip top 0-line and left 0-column
+    uint32_t *ii_start2 = ii2 + ii_lz_32 + 1; // skip top 0-line and left 0-column
+
+    if (!ii || !ii2)
+        return -1;
+
+    for (yoff = -e; yoff <= e; yoff++) {
+        for (xoff = -e; xoff <= e; xoff++) {
+            int x, y;
+
+            printf("xoff=%d yoff=%d\n", xoff, yoff);
+
+            compute_ssd_integral_image(ii_start, ii_lz_32,
+                                       src, lz, xoff, yoff, e, w, h);
+            display_integral(ii_start, ii_w, ii_h, ii_lz_32);
+
+            compute_unsafe_ssd_integral_image(ii_start2, ii_lz_32,
+                                              0, 0,
+                                              src, lz,
+                                              xoff, yoff, e, w, h,
+                                              ii_w, ii_h);
+            display_integral(ii_start2, ii_w, ii_h, ii_lz_32);
+
+            if (memcmp(ii, ii2, (ii_h+1) * ii_lz_32 * sizeof(*ii))) {
+                printf("Integral mismatch\n");
+                ret = 1;
+                goto end;
+            }
+        }
+    }
+
+end:
+    av_freep(&ii);
+    av_freep(&ii2);
+    return ret;
+}
diff --git a/libavfilter/version.h b/libavfilter/version.h
index 1a7a1b5686..93d249be10 100644
--- a/libavfilter/version.h
+++ b/libavfilter/version.h
@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   6
-#define LIBAVFILTER_VERSION_MINOR  62
+#define LIBAVFILTER_VERSION_MINOR  63
 #define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
diff --git a/libavfilter/vf_nlmeans.c b/libavfilter/vf_nlmeans.c
new file mode 100644
index 0000000000..2487813504
--- /dev/null
+++ b/libavfilter/vf_nlmeans.c
@@ -0,0 +1,551 @@
+/*
+ * Copyright (c) 2016 Clément Bœsch <u pkh me>
+ *
+ * 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
+ */
+
+/**
+ * @todo
+ * - SIMD for compute_safe_ssd_integral_image
+ * - SIMD for final weighted averaging
+ * - better automatic defaults? see "Parameters" @ http://www.ipol.im/pub/art/2011/bcm_nlm/
+ * - temporal support (probably doesn't need any displacement according to
+ *   "Denoising image sequences does not require motion estimation")
+ * - Bayer pixel format support for at least raw photos? (DNG support would be
+ *   handy here)
+ * - FATE test (probably needs visual threshold test mechanism due to the use
+ *   of floats)
+ */
+
+#include "libavutil/avassert.h"
+#include "libavutil/opt.h"
+#include "libavutil/pixdesc.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+
+struct weighted_avg {
+    double total_weight;
+    double sum;
+};
+
+#define WEIGHT_LUT_NBITS 9
+#define WEIGHT_LUT_SIZE  (1<<WEIGHT_LUT_NBITS)
+
+typedef struct {
+    const AVClass *class;
+    int nb_planes;
+    int chroma_w, chroma_h;
+    double pdiff_scale;                         // invert of the filtering parameter (sigma*10) squared
+    double sigma;                               // denoising strength
+    int patch_size,    patch_hsize;             // patch size and half size
+    int patch_size_uv, patch_hsize_uv;          // patch size and half size for chroma planes
+    int research_size,    research_hsize;       // research size and half size
+    int research_size_uv, research_hsize_uv;    // research size and half size for chroma planes
+    uint32_t *ii_orig;                          // integral image
+    uint32_t *ii;                               // integral image starting after the 0-line and 0-column
+    int ii_w, ii_h;                             // width and height of the integral image
+    int ii_lz_32;                               // linesize in 32-bit units of the integral image
+    struct weighted_avg *wa;                    // weighted average of every pixel
+    int wa_linesize;                            // linesize for wa in struct size unit
+    double weight_lut[WEIGHT_LUT_SIZE];         // lookup table mapping (scaled) patch differences to their associated weights
+    double pdiff_lut_scale;                     // scale factor for patch differences before looking into the LUT
+    int max_meaningful_diff;                    // maximum difference considered (if the patch difference is too high we ignore the pixel)
+} NLMeansContext;
+
+#define OFFSET(x) offsetof(NLMeansContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+static const AVOption nlmeans_options[] = {
+    { "s",  "denoising strength", OFFSET(sigma), AV_OPT_TYPE_DOUBLE, { .dbl = 1.0 }, 1.0, 30.0, FLAGS },
+    { "p",  "patch size",                   OFFSET(patch_size),    AV_OPT_TYPE_INT, { .i64 = 3*2+1 }, 0, 99, FLAGS },
+    { "pc", "patch size for chroma planes", OFFSET(patch_size_uv), AV_OPT_TYPE_INT, { .i64 = 0 },     0, 99, FLAGS },
+    { "r",  "research window",                   OFFSET(research_size),    AV_OPT_TYPE_INT, { .i64 = 7*2+1 }, 0, 99, FLAGS },
+    { "rc", "research window for chroma planes", OFFSET(research_size_uv), AV_OPT_TYPE_INT, { .i64 = 0 },     0, 99, FLAGS },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(nlmeans);
+
+static int query_formats(AVFilterContext *ctx)
+{
+    static const enum AVPixelFormat pix_fmts[] = {
+        AV_PIX_FMT_YUV410P, AV_PIX_FMT_YUV411P,
+        AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUV422P,
+        AV_PIX_FMT_YUV440P, AV_PIX_FMT_YUV444P,
+        AV_PIX_FMT_YUVJ444P, AV_PIX_FMT_YUVJ440P,
+        AV_PIX_FMT_YUVJ422P, AV_PIX_FMT_YUVJ420P,
+        AV_PIX_FMT_YUVJ411P,
+        AV_PIX_FMT_GRAY8, AV_PIX_FMT_GBRP,
+        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);
+}
+
+/*
+ * M is a discrete map where every entry contains the sum of all the entries
+ * in the rectangle from the top-left origin of M to its coordinate. In the
+ * following schema, "i" contains the sum of the whole map:
+ *
+ * M = +----------+-----------------+----+
+ *     |          |                 |    |
+ *     |          |                 |    |
+ *     |         a|                b|   c|
+ *     +----------+-----------------+----+
+ *     |          |                 |    |
+ *     |          |                 |    |
+ *     |          |        X        |    |
+ *     |          |                 |    |
+ *     |         d|                e|   f|
+ *     +----------+-----------------+----+
+ *     |          |                 |    |
+ *     |         g|                h|   i|
+ *     +----------+-----------------+----+
+ *
+ * The sum of the X box can be calculated with:
+ *    X = e-d-b+a
+ *
+ * See https://en.wikipedia.org/wiki/Summed_area_table
+ *
+ * The compute*_ssd functions compute the integral image M where every entry
+ * contains the sum of the squared difference of every corresponding pixels of
+ * two input planes of the same size as M.
+ */
+static inline int get_integral_patch_value(const uint32_t *ii, int ii_lz_32, int x, int y, int p)
+{
+    const int e = ii[(y + p    ) * ii_lz_32 + (x + p    )];
+    const int d = ii[(y + p    ) * ii_lz_32 + (x - p - 1)];
+    const int b = ii[(y - p - 1) * ii_lz_32 + (x + p    )];
+    const int a = ii[(y - p - 1) * ii_lz_32 + (x - p - 1)];
+    return e - d - b + a;
+}
+
+/**
+ * Compute squared difference of the safe area (the zone where s1 and s2
+ * overlap). It is likely the largest integral zone, so it is interesting to do
+ * as little checks as possible; contrary to the unsafe version of this
+ * function, we do not need any clipping here.
+ *
+ * The line above dst and the column to its left are always readable.
+ *
+ * This C version computes the SSD integral image using a scalar accumulator,
+ * while for SIMD implementation it is likely more interesting to use the
+ * two-loops algorithm variant.
+ */
+static void compute_safe_ssd_integral_image_c(uint32_t *dst, int dst_linesize_32,
+                                              const uint8_t *s1, int linesize1,
+                                              const uint8_t *s2, int linesize2,
+                                              int w, int h)
+{
+    int x, y;
+
+    for (y = 0; y < h; y++) {
+        uint32_t acc = dst[-1] - dst[-dst_linesize_32 - 1];
+
+        for (x = 0; x < w; x++) {
+            const int d  = s1[x] - s2[x];
+            acc += d * d;
+            dst[x] = dst[-dst_linesize_32 + x] + acc;
+        }
+        s1  += linesize1;
+        s2  += linesize2;
+        dst += dst_linesize_32;
+    }
+}
+
+/**
+ * Compute squared difference of an unsafe area (the zone nor s1 nor s2 could
+ * be readable).
+ *
+ * On the other hand, the line above dst and the column to its left are always
+ * readable.
+ *
+ * There is little point in having this function SIMDified as it is likely too
+ * complex and only handle small portions of the image.
+ *
+ * @param dst               integral image
+ * @param dst_linesize_32   integral image linesize (in 32-bit integers unit)
+ * @param startx            integral starting x position
+ * @param starty            integral starting y position
+ * @param src               source plane buffer
+ * @param linesize          source plane linesize
+ * @param offx              source offsetting in x
+ * @param offy              source offsetting in y
+ * @paran r                 absolute maximum source offsetting
+ * @param sw                source width
+ * @param sh                source height
+ * @param w                 width to compute
+ * @param h                 height to compute
+ */
+static inline void compute_unsafe_ssd_integral_image(uint32_t *dst, int dst_linesize_32,
+                                                     int startx, int starty,
+                                                     const uint8_t *src, int linesize,
+                                                     int offx, int offy, int r, int sw, int sh,
+                                                     int w, int h)
+{
+    int x, y;
+
+    for (y = starty; y < starty + h; y++) {
+        uint32_t acc = dst[y*dst_linesize_32 + startx - 1] - dst[(y-1)*dst_linesize_32 + startx - 1];
+        const int s1y = av_clip(y -  r,         0, sh - 1);
+        const int s2y = av_clip(y - (r + offy), 0, sh - 1);
+
+        for (x = startx; x < startx + w; x++) {
+            const int s1x = av_clip(x -  r,         0, sw - 1);
+            const int s2x = av_clip(x - (r + offx), 0, sw - 1);
+            const uint8_t v1 = src[s1y*linesize + s1x];
+            const uint8_t v2 = src[s2y*linesize + s2x];
+            const int d = v1 - v2;
+            acc += d * d;
+            dst[y*dst_linesize_32 + x] = dst[(y-1)*dst_linesize_32 + x] + acc;
+        }
+    }
+}
+
+/*
+ * Compute the sum of squared difference integral image
+ * http://www.ipol.im/pub/art/2014/57/
+ * Integral Images for Block Matching - Gabriele Facciolo, Nicolas Limare, Enric Meinhardt-Llopis
+ *
+ * @param ii                integral image of dimension (w+e*2) x (h+e*2) with
+ *                          an additional zeroed top line and column already
+ *                          "applied" to the pointer value
+ * @param ii_linesize_32    integral image linesize (in 32-bit integers unit)
+ * @param src               source plane buffer
+ * @param linesize          source plane linesize
+ * @param offx              x-offsetting ranging in [-e;e]
+ * @param offy              y-offsetting ranging in [-e;e]
+ * @param w                 source width
+ * @param h                 source height
+ * @param e                 research padding edge
+ */
+static void compute_ssd_integral_image(uint32_t *ii, int ii_linesize_32,
+                                       const uint8_t *src, int linesize, int offx, int offy,
+                                       int e, int w, int h)
+{
+    // ii has a surrounding padding of thickness "e"
+    const int ii_w = w + e*2;
+    const int ii_h = h + e*2;
+
+    // we center the first source
+    const int s1x = e;
+    const int s1y = e;
+
+    // 2nd source is the frame with offsetting
+    const int s2x = e + offx;
+    const int s2y = e + offy;
+
+    // get the dimension of the overlapping rectangle where it is always safe
+    // to compare the 2 sources pixels
+    const int startx_safe = FFMAX(s1x, s2x);
+    const int starty_safe = FFMAX(s1y, s2y);
+    const int endx_safe   = FFMIN(s1x + w, s2x + w);
+    const int endy_safe   = FFMIN(s1y + h, s2y + h);
+
+    // top part where only one of s1 and s2 is still readable, or none at all
+    compute_unsafe_ssd_integral_image(ii, ii_linesize_32,
+                                      0, 0,
+                                      src, linesize,
+                                      offx, offy, e, w, h,
+                                      ii_w, starty_safe);
+
+    // fill the left column integral required to compute the central
+    // overlapping one
+    compute_unsafe_ssd_integral_image(ii, ii_linesize_32,
+                                      0, starty_safe,
+                                      src, linesize,
+                                      offx, offy, e, w, h,
+                                      startx_safe, endy_safe - starty_safe);
+
+    // main and safe part of the integral
+    av_assert1(startx_safe - s1x >= 0); av_assert1(startx_safe - s1x < w);
+    av_assert1(starty_safe - s1y >= 0); av_assert1(starty_safe - s1y < h);
+    av_assert1(startx_safe - s2x >= 0); av_assert1(startx_safe - s2x < w);
+    av_assert1(starty_safe - s2y >= 0); av_assert1(starty_safe - s2y < h);
+    compute_safe_ssd_integral_image_c(ii + starty_safe*ii_linesize_32 + startx_safe, ii_linesize_32,
+                                      src + (starty_safe - s1y) * linesize + (startx_safe - s1x), linesize,
+                                      src + (starty_safe - s2y) * linesize + (startx_safe - s2x), linesize,
+                                      endx_safe - startx_safe, endy_safe - starty_safe);
+
+    // right part of the integral
+    compute_unsafe_ssd_integral_image(ii, ii_linesize_32,
+                                      endx_safe, starty_safe,
+                                      src, linesize,
+                                      offx, offy, e, w, h,
+                                      ii_w - endx_safe, endy_safe - starty_safe);
+
+    // bottom part where only one of s1 and s2 is still readable, or none at all
+    compute_unsafe_ssd_integral_image(ii, ii_linesize_32,
+                                      0, endy_safe,
+                                      src, linesize,
+                                      offx, offy, e, w, h,
+                                      ii_w, ii_h - endy_safe);
+}
+
+static int config_input(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    NLMeansContext *s = ctx->priv;
+    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
+    const int e = FFMAX(s->research_hsize, s->research_hsize_uv)
+                + FFMAX(s->patch_hsize,    s->patch_hsize_uv);
+
+    s->chroma_w = FF_CEIL_RSHIFT(inlink->w, desc->log2_chroma_w);
+    s->chroma_h = FF_CEIL_RSHIFT(inlink->h, desc->log2_chroma_h);
+    s->nb_planes = av_pix_fmt_count_planes(inlink->format);
+
+    /* Allocate the integral image with extra edges of thickness "e"
+     *
+     *   +_+-------------------------------+
+     *   |0|0000000000000000000000000000000|
+     *   +-x-------------------------------+
+     *   |0|\    ^                         |
+     *   |0| ii  | e                       |
+     *   |0|     v                         |
+     *   |0|   +-----------------------+   |
+     *   |0|   |                       |   |
+     *   |0|<->|                       |   |
+     *   |0| e |                       |   |
+     *   |0|   |                       |   |
+     *   |0|   +-----------------------+   |
+     *   |0|                               |
+     *   |0|                               |
+     *   |0|                               |
+     *   +-+-------------------------------+
+     */
+    s->ii_w = inlink->w + e*2;
+    s->ii_h = inlink->h + e*2;
+
+    // align to 4 the linesize, "+1" is for the space of the left 0-column
+    s->ii_lz_32 = FFALIGN(s->ii_w + 1, 4);
+
+    // "+1" is for the space of the top 0-line
+    s->ii_orig = av_mallocz_array(s->ii_h + 1, s->ii_lz_32 * sizeof(*s->ii_orig));
+    if (!s->ii_orig)
+        return AVERROR(ENOMEM);
+
+    // skip top 0-line and left 0-column
+    s->ii = s->ii_orig + s->ii_lz_32 + 1;
+
+    // allocate weighted average for every pixel
+    s->wa_linesize = inlink->w;
+    s->wa = av_malloc_array(s->wa_linesize, inlink->h * sizeof(*s->wa));
+    if (!s->wa)
+        return AVERROR(ENOMEM);
+
+    return 0;
+}
+
+struct thread_data {
+    const uint8_t *src;
+    int src_linesize;
+    int startx, starty;
+    int endx, endy;
+    const uint32_t *ii_start;
+    int p;
+};
+
+static int nlmeans_slice(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)
+{
+    int x, y;
+    NLMeansContext *s = ctx->priv;
+    const struct thread_data *td = arg;
+    const uint8_t *src = td->src;
+    const int src_linesize = td->src_linesize;
+    const int process_h = td->endy - td->starty;
+    const int slice_start = (process_h *  jobnr   ) / nb_jobs;
+    const int slice_end   = (process_h * (jobnr+1)) / nb_jobs;
+    const int starty = td->starty + slice_start;
+    const int endy   = td->starty + slice_end;
+
+    for (y = starty; y < endy; y++) {
+        for (x = td->startx; x < td->endx; x++) {
+            const int patch_diff_sq = get_integral_patch_value(td->ii_start, s->ii_lz_32, x, y, td->p);
+            if (patch_diff_sq < s->max_meaningful_diff) {
+                struct weighted_avg *wa = &s->wa[y*s->wa_linesize + x];
+                const int weight_lut_idx = patch_diff_sq * s->pdiff_lut_scale;
+                const double weight = s->weight_lut[weight_lut_idx]; // exp(-patch_diff_sq * s->pdiff_scale)
+                wa->total_weight += weight;
+                wa->sum += weight * src[y*src_linesize + x];
+            }
+        }
+    }
+    return 0;
+}
+
+static int nlmeans_plane(AVFilterContext *ctx, int w, int h, int p, int r,
+                         uint8_t *dst, int dst_linesize,
+                         const uint8_t *src, int src_linesize)
+{
+    int x, y;
+    int offx, offy;
+    NLMeansContext *s = ctx->priv;
+    /* patches center points cover the whole research window so the patches
+     * themselves overflow the research window */
+    const int e = r + p;
+    /* focus an integral pointer on the centered image (s1) */
+    const uint32_t *centered_ii = s->ii + e*s->ii_lz_32 + e;
+
+    memset(s->wa, 0, s->wa_linesize * h * sizeof(*s->wa));
+
+    for (offy = -r; offy <= r; offy++) {
+        for (offx = -r; offx <= r; offx++) {
+            if (offx || offy) {
+                struct thread_data td = {
+                    .src          = src + offy*src_linesize + offx,
+                    .src_linesize = src_linesize,
+                    .startx       = FFMAX(0, -offx),
+                    .starty       = FFMAX(0, -offy),
+                    .endx         = FFMIN(w, w - offx),
+                    .endy         = FFMIN(h, h - offy),
+                    .ii_start     = centered_ii + offy*s->ii_lz_32 + offx,
+                    .p            = p,
+                };
+
+                compute_ssd_integral_image(s->ii, s->ii_lz_32,
+                                           src, src_linesize,
+                                           offx, offy, e, w, h);
+                ctx->internal->execute(ctx, nlmeans_slice, &td, NULL,
+                                       FFMIN(td.endy - td.starty, ff_filter_get_nb_threads(ctx)));
+            }
+        }
+    }
+    for (y = 0; y < h; y++) {
+        for (x = 0; x < w; x++) {
+            struct weighted_avg *wa = &s->wa[y*s->wa_linesize + x];
+
+            // Also weight the centered pixel
+            wa->total_weight += 1.0;
+            wa->sum += 1.0 * src[y*src_linesize + x];
+
+            dst[y*dst_linesize + x] = av_clip_uint8(wa->sum / wa->total_weight);
+        }
+    }
+    return 0;
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+    int i;
+    AVFilterContext *ctx = inlink->dst;
+    NLMeansContext *s = ctx->priv;
+    AVFilterLink *outlink = ctx->outputs[0];
+
+    AVFrame *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 (i = 0; i < s->nb_planes; i++) {
+        const int w = i ? s->chroma_w          : inlink->w;
+        const int h = i ? s->chroma_h          : inlink->h;
+        const int p = i ? s->patch_hsize_uv    : s->patch_hsize;
+        const int r = i ? s->research_hsize_uv : s->research_hsize;
+        nlmeans_plane(ctx, w, h, p, r,
+                      out->data[i], out->linesize[i],
+                      in->data[i],  in->linesize[i]);
+    }
+
+    av_frame_free(&in);
+    return ff_filter_frame(outlink, out);
+}
+
+#define CHECK_ODD_FIELD(field, name) do {                       \
+    if (!(s->field & 1)) {                                      \
+        s->field |= 1;                                          \
+        av_log(ctx, AV_LOG_WARNING, name " size must be odd, "  \
+               "setting it to %d\n", s->field);                 \
+    }                                                           \
+} while (0)
+
+static av_cold int init(AVFilterContext *ctx)
+{
+    int i;
+    NLMeansContext *s = ctx->priv;
+    const double h = s->sigma * 10.;
+
+    s->pdiff_scale = 1. / (h * h);
+    s->max_meaningful_diff = -log(1/255.) / s->pdiff_scale;
+    s->pdiff_lut_scale = 1./s->max_meaningful_diff * WEIGHT_LUT_SIZE;
+    av_assert0((s->max_meaningful_diff - 1) * s->pdiff_lut_scale < FF_ARRAY_ELEMS(s->weight_lut));
+    for (i = 0; i < WEIGHT_LUT_SIZE; i++)
+        s->weight_lut[i] = exp(-i / s->pdiff_lut_scale * s->pdiff_scale);
+
+    CHECK_ODD_FIELD(research_size,   "Luma research window");
+    CHECK_ODD_FIELD(patch_size,      "Luma patch");
+
+    if (!s->research_size_uv) s->research_size_uv = s->research_size;
+    if (!s->patch_size_uv)    s->patch_size_uv    = s->patch_size;
+
+    CHECK_ODD_FIELD(research_size_uv, "Chroma research window");
+    CHECK_ODD_FIELD(patch_size_uv,    "Chroma patch");
+
+    s->research_hsize    = s->research_size    / 2;
+    s->research_hsize_uv = s->research_size_uv / 2;
+    s->patch_hsize       = s->patch_size       / 2;
+    s->patch_hsize_uv    = s->patch_size_uv    / 2;
+
+    av_log(ctx, AV_LOG_INFO, "Research window: %dx%d / %dx%d, patch size: %dx%d / %dx%d\n",
+           s->research_size, s->research_size, s->research_size_uv, s->research_size_uv,
+           s->patch_size,    s->patch_size,    s->patch_size_uv,    s->patch_size_uv);
+
+    return 0;
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    NLMeansContext *s = ctx->priv;
+    av_freep(&s->ii_orig);
+    av_freep(&s->wa);
+}
+
+static const AVFilterPad nlmeans_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .config_props = config_input,
+        .filter_frame = filter_frame,
+    },
+    { NULL }
+};
+
+static const AVFilterPad nlmeans_outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+    },
+    { NULL }
+};
+
+AVFilter ff_vf_nlmeans = {
+    .name          = "nlmeans",
+    .description   = NULL_IF_CONFIG_SMALL("Non-local means denoiser."),
+    .priv_size     = sizeof(NLMeansContext),
+    .init          = init,
+    .uninit        = uninit,
+    .query_formats = query_formats,
+    .inputs        = nlmeans_inputs,
+    .outputs       = nlmeans_outputs,
+    .priv_class    = &nlmeans_class,
+    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC | AVFILTER_FLAG_SLICE_THREADS,
+};