avfilter/vf_scdet: add filter to detect scene change

Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Limin Wang <lance.lmwang@gmail.com>

Changelog

@@ -66,6 +66,7 @@ version <next>:
 - asubboost filter
 - Pro Pinball Series Soundbank demuxer
 - pcm_rechunk bitstream filter
+- scdet filter
 
 
 version 4.2:

configure

@@ -3569,6 +3569,7 @@ sab_filter_deps="gpl swscale"
 scale2ref_filter_deps="swscale"
 scale_filter_deps="swscale"
 scale_qsv_filter_deps="libmfx"
+scdet_filter_select="scene_sad"
 select_filter_select="scene_sad"
 sharpness_vaapi_filter_deps="vaapi"
 showcqt_filter_deps="avcodec avformat swscale"

doc/filters.texi

@@ -16578,6 +16578,41 @@ Set the horizontal scrolling speed.
 Set the vertical scrolling speed.
 @end table
 
+@anchor{scdet}
+@section scdet
+
+Detect video scene change.
+
+This filter sets frame metadata with mafd between frame, the scene score, and
+forward the frame to the next filter, so they can use these metadata to detect
+scene change or others.
+
+In addition, this filter logs a message and sets frame metadata when it detects
+a scene change by @option{threshold}.
+
+@code{lavfi.scd.mafd} metadata keys are set with mafd for every frame.
+
+@code{lavfi.scd.score} metadata keys are set with scene change score for every frame
+to detect scene change.
+
+@code{lavfi.scd.time} metadata keys are set with current filtered frame time which
+detect scene change with @option{threshold}.
+
+The filter accepts the following options:
+
+@table @option
+@item threshold, t
+Set the scene change detection threshold as a percentage of maximum change. Good
+values are in the @code{[8.0, 14.0]} range. The range for @option{threshold} is
+@code{[0., 100.]}.
+
+Default value is @code{10.}.
+
+@item sc_pass, s
+Set the flag to pass scene change frames to the next filter. Default value is @code{0}
+You can enable it if you want to get snapshot of scene change frames only.
+@end table
+
 @anchor{selectivecolor}
 @section selectivecolor
 

libavfilter/Makefile

@@ -376,6 +376,7 @@ OBJS-$(CONFIG_SCALE_QSV_FILTER)              += vf_scale_qsv.o
 OBJS-$(CONFIG_SCALE_VAAPI_FILTER)            += vf_scale_vaapi.o scale_eval.o vaapi_vpp.o
 OBJS-$(CONFIG_SCALE_VULKAN_FILTER)           += vf_scale_vulkan.o vulkan.o
 OBJS-$(CONFIG_SCALE2REF_FILTER)              += vf_scale.o scale_eval.o
+OBJS-$(CONFIG_SCDET_FILTER)                  += vf_scdet.o
 OBJS-$(CONFIG_SCROLL_FILTER)                 += vf_scroll.o
 OBJS-$(CONFIG_SELECT_FILTER)                 += f_select.o
 OBJS-$(CONFIG_SELECTIVECOLOR_FILTER)         += vf_selectivecolor.o

libavfilter/allfilters.c

@@ -358,6 +358,7 @@ extern AVFilter ff_vf_scale_qsv;
 extern AVFilter ff_vf_scale_vaapi;
 extern AVFilter ff_vf_scale_vulkan;
 extern AVFilter ff_vf_scale2ref;
+extern AVFilter ff_vf_scdet;
 extern AVFilter ff_vf_scroll;
 extern AVFilter ff_vf_select;
 extern AVFilter ff_vf_selectivecolor;

libavfilter/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   7
-#define LIBAVFILTER_VERSION_MINOR  80
+#define LIBAVFILTER_VERSION_MINOR  81
 #define LIBAVFILTER_VERSION_MICRO 100
 
 

libavfilter/vf_scdet.c

+/*
+ * 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
+ * video scene change detection filter
+ */
+
+#include "libavutil/avassert.h"
+#include "libavutil/imgutils.h"
+#include "libavutil/opt.h"
+#include "libavutil/pixdesc.h"
+#include "libavutil/timestamp.h"
+
+#include "avfilter.h"
+#include "filters.h"
+#include "scene_sad.h"
+
+typedef struct SCDetContext {
+    const AVClass *class;
+
+    ptrdiff_t width[4];
+    ptrdiff_t height[4];
+    int nb_planes;
+    int bitdepth;
+    ff_scene_sad_fn sad;
+    double prev_mafd;
+    double scene_score;
+    AVFrame *prev_picref;
+    double threshold;
+    int sc_pass;
+} SCDetContext;
+
+#define OFFSET(x) offsetof(SCDetContext, x)
+#define V AV_OPT_FLAG_VIDEO_PARAM
+#define F AV_OPT_FLAG_FILTERING_PARAM
+
+static const AVOption scdet_options[] = {
+    { "threshold",   "set scene change detect threshold",        OFFSET(threshold),  AV_OPT_TYPE_DOUBLE,   {.dbl = 10.},     0,  100., V|F },
+    { "t",           "set scene change detect threshold",        OFFSET(threshold),  AV_OPT_TYPE_DOUBLE,   {.dbl = 10.},     0,  100., V|F },
+    { "sc_pass",     "Set the flag to pass scene change frames", OFFSET(sc_pass),    AV_OPT_TYPE_BOOL,     {.dbl =  0  },    0,    1,  V|F },
+    { "s",           "Set the flag to pass scene change frames", OFFSET(sc_pass),    AV_OPT_TYPE_BOOL,     {.dbl =  0  },    0,    1,  V|F },
+    {NULL}
+};
+
+AVFILTER_DEFINE_CLASS(scdet);
+
+static int query_formats(AVFilterContext *ctx)
+{
+    static const enum AVPixelFormat pix_fmts[] = {
+            AV_PIX_FMT_RGB24, AV_PIX_FMT_BGR24, AV_PIX_FMT_RGBA,
+            AV_PIX_FMT_ABGR, AV_PIX_FMT_BGRA, AV_PIX_FMT_GRAY8,
+            AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUVJ420P,
+            AV_PIX_FMT_YUV422P, AV_PIX_FMT_YUVJ422P,
+            AV_PIX_FMT_YUV440P, AV_PIX_FMT_YUVJ440P,
+            AV_PIX_FMT_YUV444P, AV_PIX_FMT_YUVJ444P,
+            AV_PIX_FMT_YUV420P9, AV_PIX_FMT_YUV420P10, AV_PIX_FMT_YUV420P12,
+            AV_PIX_FMT_YUV422P9, AV_PIX_FMT_YUV422P10, AV_PIX_FMT_YUV422P12,
+            AV_PIX_FMT_YUV444P9, AV_PIX_FMT_YUV444P10, AV_PIX_FMT_YUV444P12,
+            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(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    SCDetContext *s = ctx->priv;
+    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
+    int is_yuv = !(desc->flags & AV_PIX_FMT_FLAG_RGB) &&
+        (desc->flags & AV_PIX_FMT_FLAG_PLANAR) &&
+        desc->nb_components >= 3;
+
+    s->bitdepth = desc->comp[0].depth;
+    s->nb_planes = is_yuv ? 1 : av_pix_fmt_count_planes(inlink->format);
+
+    for (int plane = 0; plane < 4; plane++) {
+        ptrdiff_t line_size = av_image_get_linesize(inlink->format, inlink->w, plane);
+        s->width[plane] = line_size >> (s->bitdepth > 8);
+        s->height[plane] = inlink->h >> ((plane == 1 || plane == 2) ? desc->log2_chroma_h : 0);
+    }
+
+    s->sad = ff_scene_sad_get_fn(s->bitdepth == 8 ? 8 : 16);
+    if (!s->sad)
+        return AVERROR(EINVAL);
+
+    return 0;
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    SCDetContext *s = ctx->priv;
+
+    av_frame_free(&s->prev_picref);
+}
+
+static double get_scene_score(AVFilterContext *ctx, AVFrame *frame)
+{
+    double ret = 0;
+    SCDetContext *s = ctx->priv;
+    AVFrame *prev_picref = s->prev_picref;
+
+    if (prev_picref && frame->height == prev_picref->height
+                    && frame->width  == prev_picref->width) {
+        uint64_t sad = 0;
+        double mafd, diff;
+        uint64_t count = 0;
+
+        for (int plane = 0; plane < s->nb_planes; plane++) {
+            uint64_t plane_sad;
+            s->sad(prev_picref->data[plane], prev_picref->linesize[plane],
+                    frame->data[plane], frame->linesize[plane],
+                    s->width[plane], s->height[plane], &plane_sad);
+            sad += plane_sad;
+            count += s->width[plane] * s->height[plane];
+        }
+
+        emms_c();
+        mafd = (double)sad * 100. / count / (1ULL << s->bitdepth);
+        diff = fabs(mafd - s->prev_mafd);
+        ret  = av_clipf(FFMIN(mafd, diff), 0, 100.);
+        s->prev_mafd = mafd;
+        av_frame_free(&prev_picref);
+    }
+    s->prev_picref = av_frame_clone(frame);
+    return ret;
+}
+
+static int set_meta(SCDetContext *s, AVFrame *frame, const char *key, const char *value)
+{
+    return av_dict_set(&frame->metadata, key, value, 0);
+}
+
+static int activate(AVFilterContext *ctx)
+{
+    int ret;
+    AVFilterLink *inlink = ctx->inputs[0];
+    AVFilterLink *outlink = ctx->outputs[0];
+    SCDetContext *s = ctx->priv;
+    AVFrame *frame;
+
+    FF_FILTER_FORWARD_STATUS_BACK(outlink, inlink);
+
+    ret = ff_inlink_consume_frame(inlink, &frame);
+    if (ret < 0)
+        return ret;
+
+    if (frame) {
+        char buf[64];
+        s->scene_score = get_scene_score(ctx, frame);
+        snprintf(buf, sizeof(buf), "%0.3f", s->prev_mafd);
+        set_meta(s, frame, "lavfi.scd.mafd", buf);
+        snprintf(buf, sizeof(buf), "%0.3f", s->scene_score);
+        set_meta(s, frame, "lavfi.scd.score", buf);
+
+        if (s->scene_score > s->threshold) {
+            av_log(s, AV_LOG_INFO, "lavfi.scd.score: %.3f, lavfi.scd.time: %s\n",
+                    s->scene_score, av_ts2timestr(frame->pts, &inlink->time_base));
+            set_meta(s, frame, "lavfi.scd.time",
+                    av_ts2timestr(frame->pts, &inlink->time_base));
+        }
+        if (s->sc_pass) {
+            if (s->scene_score > s->threshold)
+                return ff_filter_frame(outlink, frame);
+            else {
+                av_frame_free(&frame);
+            }
+        } else
+            return ff_filter_frame(outlink, frame);
+    }
+
+    FF_FILTER_FORWARD_STATUS(inlink, outlink);
+    FF_FILTER_FORWARD_WANTED(outlink, inlink);
+
+    return FFERROR_NOT_READY;
+}
+
+static const AVFilterPad scdet_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .config_props = config_input,
+    },
+    { NULL }
+};
+
+static const AVFilterPad scdet_outputs[] = {
+    {
+        .name          = "default",
+        .type          = AVMEDIA_TYPE_VIDEO,
+    },
+    { NULL }
+};
+
+AVFilter ff_vf_scdet = {
+    .name          = "scdet",
+    .description   = NULL_IF_CONFIG_SMALL("Detect video scene change"),
+    .priv_size     = sizeof(SCDetContext),
+    .priv_class    = &scdet_class,
+    .uninit        = uninit,
+    .query_formats = query_formats,
+    .inputs        = scdet_inputs,
+    .outputs       = scdet_outputs,
+    .activate      = activate,
+};