Port MPlayer blackframe filter.

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Subject: [FFmpeg-devel] [PATCH] Port MPlayer blackframe filter.
Date: Sun, 26 Sep 2010 01:10:40 +0200

Originally committed as revision 25214 to svn://svn.ffmpeg.org/ffmpeg/trunk

Changelog

@@ -41,6 +41,7 @@ version <next>:
 - make the crop filter accept parametric expressions
 - make ffprobe accept AVFormatContext options
 - yadif filter
+- blackframe filter
 
 
 version 0.6:

configure

@@ -1401,6 +1401,7 @@ tcp_protocol_deps="network"
 udp_protocol_deps="network"
 
 # filters
+blackframe_filter_deps="gpl"
 ocv_smooth_filter_deps="libopencv"
 yadif_filter_deps="gpl"
 

doc/filters.texi

@@ -71,6 +71,27 @@ build.
 
 Below is a description of the currently available video filters.
 
+@section blackframe
+
+Detect frames that are (almost) completely black. Can be useful to
+detect chapter transitions or commercials. Output lines consist of
+the frame number of the detected frame, the percentage of blackness,
+the position in the file if known or -1 and the timestamp in seconds.
+
+In order to display the output lines, you need to set the loglevel at
+least to the AV_LOG_INFO value.
+
+The filter accepts the syntax:
+@example
+blackframe[=@var{amount}:[@var{threshold}]]
+@end example
+
+@var{amount} is the percentage of the pixels that have to be below the
+threshold, and defaults to 98.
+
+@var{threshold} is the threshold below which a pixel value is
+considered black, and defaults to 32.
+
 @section crop
 
 Crop the input video to @var{out_w}:@var{out_h}:@var{x}:@var{y}.

libavfilter/Makefile

@@ -21,6 +21,7 @@ OBJS-$(CONFIG_ANULLSRC_FILTER)               += asrc_anullsrc.o
 OBJS-$(CONFIG_ANULLSINK_FILTER)              += asink_anullsink.o
 
 OBJS-$(CONFIG_ASPECT_FILTER)                 += vf_aspect.o
+OBJS-$(CONFIG_BLACKFRAME_FILTER)             += vf_blackframe.o
 OBJS-$(CONFIG_CROP_FILTER)                   += vf_crop.o
 OBJS-$(CONFIG_FIFO_FILTER)                   += vf_fifo.o
 OBJS-$(CONFIG_FORMAT_FILTER)                 += vf_format.o

libavfilter/allfilters.c

@@ -41,6 +41,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER (ANULLSINK,   anullsink,   asink);
 
     REGISTER_FILTER (ASPECT,      aspect,      vf);
+    REGISTER_FILTER (BLACKFRAME,  blackframe,  vf);
     REGISTER_FILTER (CROP,        crop,        vf);
     REGISTER_FILTER (FIFO,        fifo,        vf);
     REGISTER_FILTER (FORMAT,      format,      vf);

libavfilter/avfilter.h

@@ -25,7 +25,7 @@
 #include "libavutil/avutil.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  1
-#define LIBAVFILTER_VERSION_MINOR 45
+#define LIBAVFILTER_VERSION_MINOR 46
 #define LIBAVFILTER_VERSION_MICRO  0
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \

libavfilter/vf_blackframe.c

@@ -0,0 +1,129 @@
+/*
+ * Copyright (C) 2010 Stefano Sabatini
+ * Copyright (C) 2006 Ivo van Poorten
+ * Copyright (C) 2006 Julian Hall
+ * Copyright (C) 2002-2003 Brian J. Murrell
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU 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
+ * Search for black frames to detect scene transitions.
+ * Ported from MPlayer libmpcodecs/vf_blackframe.c.
+ */
+
+#include "avfilter.h"
+
+typedef struct {
+    unsigned int bamount; ///< black amount
+    unsigned int bthresh; ///< black threshold
+    unsigned int frame;   ///< frame number
+    unsigned int nblack;  ///< number of black pixels counted so far
+} BlackFrameContext;
+
+static int query_formats(AVFilterContext *ctx)
+{
+    static const enum PixelFormat pix_fmts[] = {
+        PIX_FMT_YUV410P, PIX_FMT_YUV420P, PIX_FMT_GRAY8, PIX_FMT_NV12,
+        PIX_FMT_NV21, PIX_FMT_YUV444P, PIX_FMT_YUV422P, PIX_FMT_YUV411P,
+        PIX_FMT_NONE
+    };
+
+    avfilter_set_common_formats(ctx, avfilter_make_format_list(pix_fmts));
+    return 0;
+}
+
+static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
+{
+    BlackFrameContext *blackframe = ctx->priv;
+
+    blackframe->bamount = 98;
+    blackframe->bthresh = 32;
+    blackframe->nblack = 0;
+    blackframe->frame = 0;
+
+    if (args)
+        sscanf(args, "%u:%u", &blackframe->bamount, &blackframe->bthresh);
+
+    av_log(ctx, AV_LOG_INFO, "bamount:%u bthresh:%u\n",
+           blackframe->bamount, blackframe->bthresh);
+
+    if (blackframe->bamount > 100 || blackframe->bthresh > 255) {
+        av_log(ctx, AV_LOG_ERROR, "Too big value for bamount (max is 100) or bthresh (max is 255)\n");
+        return AVERROR(EINVAL);
+    }
+
+    return 0;
+}
+
+static void draw_slice(AVFilterLink *inlink, int y, int h, int slice_dir)
+{
+    AVFilterContext *ctx = inlink->dst;
+    BlackFrameContext *blackframe = ctx->priv;
+    AVFilterBufferRef *picref = inlink->cur_buf;
+    int x, i;
+    uint8_t *p = picref->data[0] + y * picref->linesize[0];
+
+    for (i = 0; i < h; i++) {
+        for (x = 0; x < inlink->w; x++)
+            blackframe->nblack += p[x] < blackframe->bthresh;
+        p += picref->linesize[0];
+    }
+
+    avfilter_draw_slice(ctx->outputs[0], y, h, slice_dir);
+}
+
+static void end_frame(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    BlackFrameContext *blackframe = ctx->priv;
+    AVFilterBufferRef *picref = inlink->cur_buf;
+    int pblack = 0;
+
+    pblack = blackframe->nblack * 100 / (inlink->w * inlink->h);
+    if (pblack >= blackframe->bamount)
+        av_log(ctx, AV_LOG_INFO, "frame:%u pblack:%u pos:%"PRId64" pts:%f\n",
+               blackframe->frame, pblack, picref->pos,
+               picref->pts == AV_NOPTS_VALUE ? -1 : (double)picref->pts / AV_TIME_BASE);
+
+    blackframe->frame++;
+    blackframe->nblack = 0;
+    avfilter_end_frame(inlink->dst->outputs[0]);
+}
+
+AVFilter avfilter_vf_blackframe = {
+    .name        = "blackframe",
+    .description = NULL_IF_CONFIG_SMALL("Detect frames that are (almost) black."),
+
+    .priv_size = sizeof(BlackFrameContext),
+    .init      = init,
+
+    .query_formats = query_formats,
+
+    .inputs    = (AVFilterPad[]) {{ .name = "default",
+                                    .type             = AVMEDIA_TYPE_VIDEO,
+                                    .draw_slice       = draw_slice,
+                                    .get_video_buffer = avfilter_null_get_video_buffer,
+                                    .start_frame      = avfilter_null_start_frame,
+                                    .end_frame        = end_frame, },
+                                  { .name = NULL}},
+
+    .outputs   = (AVFilterPad[]) {{ .name             = "default",
+                                    .type             = AVMEDIA_TYPE_VIDEO },
+                                  { .name = NULL}},
+};