[FFmpeg-devel] [PATCH] lavfi: add tdiff filter

[Stefano Sabatini]

TODO: bump minor
---
 Changelog                |   1 +
 doc/filters.texi         |   4 ++
 libavfilter/Makefile     |   1 +
 libavfilter/allfilters.c |   1 +
 libavfilter/vf_tdiff.c   | 131 +++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 138 insertions(+)
 create mode 100644 libavfilter/vf_tdiff.c

diff --git a/Changelog b/Changelog
index 5f38aea..41fdf18 100644
--- a/Changelog
+++ b/Changelog
@@ -15,6 +15,7 @@ version <next>:
 - ffserver supports codec private options
 - creating DASH compatible fragmented MP4, MPEG-DASH segmenting muxer
 - WebP muxer with animated WebP support
+- tdiff filter
 
 
 version 2.4:
diff --git a/doc/filters.texi b/doc/filters.texi
index 8c16c7a..9882da7 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -8394,6 +8394,10 @@ Useful for enlarging pixel art images without reducing sharpness.
 @section swapuv
 Swap U & V plane.
 
+ at section tdiff
+
+Show difference between consecutive frames.
+
 @section telecine
 
 Apply telecine process to the video.
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 2c56e38..3217c99 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -97,6 +97,7 @@ OBJS-$(CONFIG_BLACKDETECT_FILTER)            += vf_blackdetect.o
 OBJS-$(CONFIG_BLACKFRAME_FILTER)             += vf_blackframe.o
 OBJS-$(CONFIG_BLEND_FILTER)                  += vf_blend.o dualinput.o framesync.o
 OBJS-$(CONFIG_BOXBLUR_FILTER)                += vf_boxblur.o
+OBJS-$(CONFIG_CDIFF_FILTER)                  += vf_cdiff.o
 OBJS-$(CONFIG_CODECVIEW_FILTER)              += vf_codecview.o
 OBJS-$(CONFIG_COLORBALANCE_FILTER)           += vf_colorbalance.o
 OBJS-$(CONFIG_COLORCHANNELMIXER_FILTER)      += vf_colorchannelmixer.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 2352d44..4d065a9 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -201,6 +201,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER(SUBTITLES,      subtitles,      vf);
     REGISTER_FILTER(SUPER2XSAI,     super2xsai,     vf);
     REGISTER_FILTER(SWAPUV,         swapuv,         vf);
+    REGISTER_FILTER(TDIFF,          tdiff,          vf);
     REGISTER_FILTER(TELECINE,       telecine,       vf);
     REGISTER_FILTER(THUMBNAIL,      thumbnail,      vf);
     REGISTER_FILTER(TILE,           tile,           vf);
diff --git a/libavfilter/vf_tdiff.c b/libavfilter/vf_tdiff.c
new file mode 100644
index 0000000..82dceef
--- /dev/null
+++ b/libavfilter/vf_tdiff.c
@@ -0,0 +1,131 @@
+/*
+ * Copyright (c) 2014 Stefano Sabatini
+ *
+ * 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
+ * Consecutive frames diff filter.
+ */
+
+#include "libavutil/colorspace.h"
+#include "libavutil/common.h"
+#include "libavutil/opt.h"
+#include "libavutil/eval.h"
+#include "libavutil/pixdesc.h"
+#include "libavutil/parseutils.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+
+typedef struct {
+    const AVClass *class;
+    AVFrame *prev_frame;
+} TDiffContext;
+
+static int query_formats(AVFilterContext *ctx)
+{
+    static const enum AVPixelFormat pix_fmts[] = {
+        AV_PIX_FMT_GRAY8, AV_PIX_FMT_NONE
+    };
+
+    ff_set_common_formats(ctx, ff_make_format_list(pix_fmts));
+    return 0;
+}
+
+static int config_output(AVFilterLink *outlink)
+{
+    outlink->flags |= FF_LINK_FLAG_REQUEST_LOOP;
+    return 0;
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
+{
+    TDiffContext *tdiff = inlink->dst->priv;
+    AVFilterLink *outlink = inlink->dst->outputs[0];
+
+    if (tdiff->prev_frame) {
+        int i, j;
+
+        AVFrame *diff = ff_get_video_buffer(outlink, outlink->w, outlink->h);
+        av_frame_copy_props(frame, diff);
+        if (!diff) {
+            av_frame_free(&frame);
+            return AVERROR(ENOMEM);
+        }
+
+        /* compute difference with previous frame */
+        for (i = 0; i < frame->height; i++) {
+            uint8_t *pdiff = diff             ->data[0] + i * diff             ->linesize[0];
+            uint8_t *pprev = tdiff->prev_frame->data[0] + i * tdiff->prev_frame->linesize[0];
+            uint8_t *pthis = frame            ->data[0] + i * frame            ->linesize[0];
+            for (j = 0; j < frame->width; j++) {
+                *pdiff++ = abs(*pthis++ - *pprev++);
+            }
+        }
+
+        av_frame_free(&tdiff->prev_frame);
+        tdiff->prev_frame = frame;
+        return ff_filter_frame(outlink, diff);
+    }
+    tdiff->prev_frame = frame;
+    return 0;
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    TDiffContext *tdiff = ctx->priv;
+    av_freep(&tdiff->prev_frame);
+}
+
+static const AVOption tdiff_options[] = {
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(tdiff);
+
+static const AVFilterPad tdiff_inputs[] = {
+    {
+        .name           = "default",
+        .type           = AVMEDIA_TYPE_VIDEO,
+        .filter_frame   = filter_frame,
+        .needs_writable = 0,
+    },
+    { NULL }
+};
+
+static const AVFilterPad tdiff_outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+        .config_props  = config_output,
+    },
+    { NULL }
+};
+
+AVFilter ff_vf_tdiff = {
+    .name          = "tdiff",
+    .description   = NULL_IF_CONFIG_SMALL("Show difference with previous frame."),
+    .priv_size     = sizeof(TDiffContext),
+    .priv_class    = &tdiff_class,
+    .query_formats = query_formats,
+    .uninit        = uninit,
+    .inputs        = tdiff_inputs,
+    .outputs       = tdiff_outputs,
+};
-- 
1.8.3.2