avfilter: add entropy filter

Signed-off-by: Paul B Mahol <onemda@gmail.com>

Changelog

@@ -31,6 +31,7 @@ version <next>:
 - Dropped support for building for Windows XP. The minimum supported Windows
   version is Windows Vista.
 - deconvolve video filter
+- entropy video filter
 
 
 version 3.4:

doc/filters.texi

@@ -8220,6 +8220,20 @@ Set pal8 output pixel format. This option does not work with codebook
 length greater than 256.
 @end table
 
+@section entropy
+
+Measure graylevel entropy in histogram of color channels of video frames.
+
+It accepts the following parameters:
+
+@table @option
+@item mode
+Can be either @var{normal} or @var{diff}. Default is @var{normal}.
+
+@var{diff} mode measures entropy of histogram delta values, absolute differences
+between neighbour histogram values.
+@end table
+
 @section fade
 
 Apply a fade-in/out effect to the input video.

libavfilter/Makefile

@@ -184,6 +184,7 @@ OBJS-$(CONFIG_DRAWGRID_FILTER)               += vf_drawbox.o
 OBJS-$(CONFIG_DRAWTEXT_FILTER)               += vf_drawtext.o
 OBJS-$(CONFIG_EDGEDETECT_FILTER)             += vf_edgedetect.o
 OBJS-$(CONFIG_ELBG_FILTER)                   += vf_elbg.o
+OBJS-$(CONFIG_ENTROPY_FILTER)                += vf_entropy.o
 OBJS-$(CONFIG_EQ_FILTER)                     += vf_eq.o
 OBJS-$(CONFIG_EROSION_FILTER)                += vf_neighbor.o
 OBJS-$(CONFIG_EXTRACTPLANES_FILTER)          += vf_extractplanes.o

libavfilter/allfilters.c

@@ -194,6 +194,7 @@ static void register_all(void)
     REGISTER_FILTER(DRAWTEXT,       drawtext,       vf);
     REGISTER_FILTER(EDGEDETECT,     edgedetect,     vf);
     REGISTER_FILTER(ELBG,           elbg,           vf);
+    REGISTER_FILTER(ENTROPY,        entropy,        vf);
     REGISTER_FILTER(EQ,             eq,             vf);
     REGISTER_FILTER(EROSION,        erosion,        vf);
     REGISTER_FILTER(EXTRACTPLANES,  extractplanes,  vf);

libavfilter/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   7
-#define LIBAVFILTER_VERSION_MINOR   8
+#define LIBAVFILTER_VERSION_MINOR   9
 #define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \

libavfilter/vf_entropy.c

@@ -0,0 +1,206 @@
+/*
+ * Copyright (c) 2017 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 "drawutils.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+
+typedef struct EntropyContext {
+    const AVClass *class;
+
+    int mode;
+
+    int nb_planes;
+    int planeheight[4];
+    int planewidth[4];
+    int depth;
+    int is_rgb;
+    uint8_t rgba_map[4];
+    char planenames[4];
+    int64_t *histogram;
+} EntropyContext;
+
+#define OFFSET(x) offsetof(EntropyContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+static const AVOption entropy_options[] = {
+    { "mode", "set kind of histogram entropy measurement",  OFFSET(mode), AV_OPT_TYPE_INT,   {.i64=0}, 0, 1, FLAGS, "mode" },
+    { "normal", NULL,                                       0,            AV_OPT_TYPE_CONST, {.i64=0}, 0, 0, FLAGS, "mode" },
+    { "diff",   NULL,                                       0,            AV_OPT_TYPE_CONST, {.i64=1}, 0, 0, FLAGS, "mode" },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(entropy);
+
+static int query_formats(AVFilterContext *ctx)
+{
+    static const enum AVPixelFormat pixfmts[] = {
+        AV_PIX_FMT_YUV444P, AV_PIX_FMT_YUV422P, AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUV411P,
+        AV_PIX_FMT_YUV440P,
+        AV_PIX_FMT_YUVJ422P, AV_PIX_FMT_YUVJ444P, AV_PIX_FMT_YUVJ420P, AV_PIX_FMT_YUVJ411P,
+        AV_PIX_FMT_YUVJ440P,
+        AV_PIX_FMT_YUV444P9, AV_PIX_FMT_YUV422P9, AV_PIX_FMT_YUV420P9,
+        AV_PIX_FMT_YUV444P10, AV_PIX_FMT_YUV422P10, AV_PIX_FMT_YUV420P10,
+        AV_PIX_FMT_YUV440P10,
+        AV_PIX_FMT_YUV444P12, AV_PIX_FMT_YUV422P12, AV_PIX_FMT_YUV420P12,
+        AV_PIX_FMT_YUV440P12,
+        AV_PIX_FMT_YUV444P14, AV_PIX_FMT_YUV422P14, AV_PIX_FMT_YUV420P14,
+        AV_PIX_FMT_YUV444P16, AV_PIX_FMT_YUV422P16, AV_PIX_FMT_YUV420P16,
+        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_GRAY8, AV_PIX_FMT_GRAY9, AV_PIX_FMT_GRAY10, AV_PIX_FMT_GRAY12, AV_PIX_FMT_GRAY16,
+        AV_PIX_FMT_NONE
+    };
+
+    AVFilterFormats *formats = ff_make_format_list(pixfmts);
+    if (!formats)
+        return AVERROR(ENOMEM);
+    return ff_set_common_formats(ctx, formats);
+}
+
+static int config_input(AVFilterLink *inlink)
+{
+    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
+    AVFilterContext *ctx = inlink->dst;
+    EntropyContext *s = ctx->priv;
+
+    s->nb_planes = desc->nb_components;
+
+    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->depth = desc->comp[0].depth;
+    s->is_rgb = ff_fill_rgba_map(s->rgba_map, inlink->format) >= 0;
+
+    s->planenames[0] = s->is_rgb ? 'R' : 'Y';
+    s->planenames[1] = s->is_rgb ? 'G' : 'U';
+    s->planenames[2] = s->is_rgb ? 'B' : 'V';
+    s->planenames[3] = 'A';
+
+    s->histogram = av_malloc_array(1 << s->depth, sizeof(*s->histogram));
+    if (!s->histogram)
+        return AVERROR(ENOMEM);
+
+    return 0;
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+    AVFilterContext *ctx = inlink->dst;
+    AVFilterLink *outlink = ctx->outputs[0];
+    EntropyContext *s = ctx->priv;
+    int plane, y, x;
+
+    for (plane = 0; plane < s->nb_planes; plane++) {
+        int cidx = s->is_rgb ? s->rgba_map[plane] : plane;
+        const uint8_t *src8 = in->data[plane];
+        const uint16_t *src16 = (const uint16_t *)in->data[plane];
+        float total = s->planewidth[plane] * s->planeheight[plane];
+        float entropy = 0;
+        char metabuf[128];
+        char key[128];
+
+        memset(s->histogram, 0, (1 << s->depth) * sizeof(*s->histogram));
+
+        if (s->depth <= 8) {
+            for (y = 0; y < s->planeheight[plane]; y++) {
+                for (x = 0; x < s->planewidth[plane]; x++) {
+                    s->histogram[src8[x]]++;
+                }
+
+                src8 += in->linesize[plane];
+            }
+        } else {
+            for (y = 0; y < s->planeheight[plane]; y++) {
+                for (x = 0; x < s->planewidth[plane]; x++) {
+                    s->histogram[src16[x]]++;
+                }
+
+                src16 += in->linesize[plane] / 2;
+            }
+        }
+
+        for (y = 0; y < 1 << s->depth; y++) {
+            if (s->mode == 0) {
+                if (s->histogram[y]) {
+                    float p = s->histogram[y] / total;
+                    entropy += -log2(p) * p;
+                }
+            } else if (s->mode == 1) {
+                if (y && (s->histogram[y] - s->histogram[y - 1]) != 0) {
+                    float p = FFABS(s->histogram[y] - s->histogram[y - 1]) / total;
+                    entropy += -log2(p) * p;
+                }
+            }
+        }
+
+        snprintf(key, sizeof(key), "lavfi.entropy.entropy.%s.%c", s->mode ? "diff" : "normal", s->planenames[cidx]);
+        snprintf(metabuf, sizeof(metabuf), "%f", entropy);
+        av_dict_set(&in->metadata, key, metabuf, 0);
+        snprintf(key, sizeof(key), "lavfi.entropy.normalized_entropy.%s.%c", s->mode ? "diff" : "normal", s->planenames[cidx]);
+        snprintf(metabuf, sizeof(metabuf), "%f", entropy / log2(1 << s->depth));
+        av_dict_set(&in->metadata, key, metabuf, 0);
+    }
+
+    return ff_filter_frame(outlink, in);
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    EntropyContext *s = ctx->priv;
+
+    av_freep(&s->histogram);
+}
+
+static const AVFilterPad inputs[] = {
+    {
+        .name           = "default",
+        .type           = AVMEDIA_TYPE_VIDEO,
+        .filter_frame   = filter_frame,
+        .config_props   = config_input,
+    },
+    { NULL }
+};
+
+static const AVFilterPad outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+    },
+    { NULL }
+};
+
+AVFilter ff_vf_entropy = {
+    .name           = "entropy",
+    .description    = NULL_IF_CONFIG_SMALL("Measure video frames entropy."),
+    .priv_size      = sizeof(EntropyContext),
+    .uninit         = uninit,
+    .query_formats  = query_formats,
+    .inputs         = inputs,
+    .outputs        = outputs,
+    .priv_class     = &entropy_class,
+    .flags          = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC,
+};