[FFmpeg-devel] [PATCH] lavfi: add blackdetect filter
Stefano Sabatini
stefasab at gmail.com
Fri Mar 2 16:46:20 CET 2012
Address trac ticket #901.
---
doc/filters.texi | 50 ++++++++++
libavfilter/Makefile | 1 +
libavfilter/allfilters.c | 1 +
libavfilter/vf_blackdetect.c | 209 ++++++++++++++++++++++++++++++++++++++++++
4 files changed, 261 insertions(+), 0 deletions(-)
create mode 100644 libavfilter/vf_blackdetect.c
diff --git a/doc/filters.texi b/doc/filters.texi
index 238401a..b5e8954 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -761,6 +761,56 @@ video, use the command:
ass=sub.ass
@end example
+ at section blackdetect
+
+Detect black video intervals 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 start, end and
+duration of the detected black interval expressed in seconds.
+
+In order to display the output lines, you need to set the loglevel at
+least to the AV_LOG_INFO value.
+
+This filter accepts a list of options in the form of
+ at var{key}=@var{value} pairs separated by ":". A description of the
+accepted options follows.
+
+ at table @option
+ at item min_black_duration, d
+Set the minimum detected black duration expressed in seconds. It must
+be a non-negative floating point number.
+
+Default value is 2.0 seconds.
+
+ at item picture_black_ratio_th, pic_th
+Set the threshold for considering a picture "black".
+Express the minimum value for the ratio:
+ at example
+ at var{nb_black_pixels} / @var{nb_pixels}
+ at end example
+
+for which a picture is considered black.
+Default value is 0.98.
+
+ at item pixel_black_th, pix_th
+Set the threshold for considering a pixel "black".
+
+Express the maximum pixel luminance value for which a pixel is
+considered "black". The value is scaled according to the pixel format
+luminance range, following the equation below:
+ at example
+ at var{absolute_threshold} = @var{minimum_luminance_value} + @var{pixel_black_th} * @var{luminance_range}
+ at end example
+
+Default value is 0.10.
+ at end table
+
+The following example sets the maximum pixel threshold to the minimum
+value, and detects only black intervals of 2 or more seconds:
+ at example
+blackdetect=d=2:pix_th=0.00
+ at end example
+
@section blackframe
Detect frames that are (almost) completely black. Can be useful to
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 6e7379c..df3a27f 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -48,6 +48,7 @@ OBJS-$(CONFIG_ABUFFERSINK_FILTER) += sink_buffer.o
OBJS-$(CONFIG_ANULLSINK_FILTER) += asink_anullsink.o
OBJS-$(CONFIG_ASS_FILTER) += vf_ass.o
+OBJS-$(CONFIG_BLACKDETECT_FILTER) += vf_blackdetect.o
OBJS-$(CONFIG_BLACKFRAME_FILTER) += vf_blackframe.o
OBJS-$(CONFIG_BOXBLUR_FILTER) += vf_boxblur.o
OBJS-$(CONFIG_COPY_FILTER) += vf_copy.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 487738a..f6230be 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -56,6 +56,7 @@ void avfilter_register_all(void)
REGISTER_FILTER (ANULLSINK, anullsink, asink);
REGISTER_FILTER (ASS, ass, vf);
+ REGISTER_FILTER (BLACKDETECT, blackdetect, vf);
REGISTER_FILTER (BLACKFRAME, blackframe, vf);
REGISTER_FILTER (BOXBLUR, boxblur, vf);
REGISTER_FILTER (COPY, copy, vf);
diff --git a/libavfilter/vf_blackdetect.c b/libavfilter/vf_blackdetect.c
new file mode 100644
index 0000000..63336cd
--- /dev/null
+++ b/libavfilter/vf_blackdetect.c
@@ -0,0 +1,209 @@
+/*
+ * Copyright (c) 2012 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
+ * Video black detector, loosely based on blackframe with extended
+ * syntax and features
+ */
+
+#include <float.h>
+#include "libavutil/opt.h"
+#include "libavutil/timestamp.h"
+#include "avfilter.h"
+#include "internal.h"
+
+typedef struct {
+ const AVClass *class;
+ double min_black_duration_time; ///< minimum duration of detected black, in seconds
+ double min_black_duration; ///< minimum duration of detected black, in seconds
+ int64_t black_start; ///< pts start time of the first black picture
+ int64_t black_end; ///< pts end time of the last black picture
+ int black_started;
+
+ double picture_black_ratio_th;
+ double pixel_black_th;
+ unsigned int pixel_black_th_i;
+
+ unsigned int frame_count; ///< frame number
+ unsigned int nb_black_pixels; ///< number of black pixels counted so far
+} BlackDetectContext;
+
+#define OFFSET(x) offsetof(BlackDetectContext, x)
+static const AVOption blackdetect_options[] = {
+ { "d", "set minimum detected black duration in seconds", OFFSET(min_black_duration_time), AV_OPT_TYPE_DOUBLE, {.dbl=2}, 0, FLT_MAX},
+ { "min_black_duration", "set minimum detected black duration in seconds", OFFSET(min_black_duration_time), AV_OPT_TYPE_DOUBLE, {.dbl=2}, 0, FLT_MAX},
+ { "picture_black_ratio_th", "set the picture black ratio threshold", OFFSET(picture_black_ratio_th), AV_OPT_TYPE_DOUBLE, {.dbl=.98}, 0, 1},
+ { "pic_th", "set the picture black ratio threshold", OFFSET(picture_black_ratio_th), AV_OPT_TYPE_DOUBLE, {.dbl=.98}, 0, 1},
+ { "pixel_black_th", "set the pixel black threshold", OFFSET(pixel_black_th), AV_OPT_TYPE_DOUBLE, {.dbl=.10}, 0, 1},
+ { "pix_th", "set the pixel black threshold", OFFSET(pixel_black_th), AV_OPT_TYPE_DOUBLE, {.dbl=.10}, 0, 1},
+ { NULL },
+};
+
+static const char *blackdetect_get_name(void *ctx)
+{
+ return "blackdetect";
+}
+
+static const AVClass blackdetect_class = {
+ .class_name = "BlackDetectContext",
+ .item_name = blackdetect_get_name,
+ .option = blackdetect_options,
+};
+
+#define YUVJ_FORMATS \
+ PIX_FMT_YUVJ420P, PIX_FMT_YUVJ422P, PIX_FMT_YUVJ444P, PIX_FMT_YUVJ440P
+
+static enum PixelFormat yuvj_formats[] = {
+ YUVJ_FORMATS, PIX_FMT_NONE
+};
+
+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,
+ YUVJ_FORMATS,
+ PIX_FMT_NONE
+ };
+
+ avfilter_set_common_pixel_formats(ctx, avfilter_make_format_list(pix_fmts));
+ return 0;
+}
+
+static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
+{
+ int ret;
+ BlackDetectContext *blackdetect = ctx->priv;
+
+ blackdetect->class = &blackdetect_class;
+ av_opt_set_defaults(blackdetect);
+
+ if ((ret = av_set_options_string(blackdetect, args, "=", ":")) < 0) {
+ av_log(ctx, AV_LOG_ERROR, "Error parsing options string: '%s'\n", args);
+ return ret;
+ }
+
+ return 0;
+}
+
+static int config_input(AVFilterLink *inlink)
+{
+ AVFilterContext *ctx = inlink->dst;
+ BlackDetectContext *blackdetect = ctx->priv;
+
+ blackdetect->min_black_duration =
+ blackdetect->min_black_duration_time / av_q2d(inlink->time_base);
+
+ blackdetect->pixel_black_th_i = ff_fmt_is_in(inlink->format, yuvj_formats) ?
+ blackdetect->pixel_black_th * 255 :
+ 16 + blackdetect->pixel_black_th * (235 - 16);
+
+ av_log(blackdetect, AV_LOG_INFO,
+ "min_black_duration:%s pixel_black_th:%f pixel_black_th_i:%d picture_black_ratio_th:%f\n",
+ av_ts2timestr(blackdetect->min_black_duration, &inlink->time_base),
+ blackdetect->pixel_black_th, blackdetect->pixel_black_th_i,
+ blackdetect->picture_black_ratio_th);
+ return 0;
+}
+
+static void draw_slice(AVFilterLink *inlink, int y, int h, int slice_dir)
+{
+ AVFilterContext *ctx = inlink->dst;
+ BlackDetectContext *blackdetect = 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++)
+ blackdetect->nb_black_pixels += p[x] <= blackdetect->pixel_black_th_i;
+ p += picref->linesize[0];
+ }
+
+ avfilter_draw_slice(ctx->outputs[0], y, h, slice_dir);
+}
+
+static void end_frame(AVFilterLink *inlink)
+{
+ AVFilterContext *ctx = inlink->dst;
+ BlackDetectContext *blackdetect = ctx->priv;
+ AVFilterBufferRef *picref = inlink->cur_buf;
+ double picture_black_ratio = 0;
+
+ picture_black_ratio = (double)blackdetect->nb_black_pixels / (inlink->w * inlink->h);
+
+ av_log(ctx, AV_LOG_DEBUG,
+ "frame:%u picture_black_ratio:%f pos:%"PRId64" pts:%s t:%s type:%c\n",
+ blackdetect->frame_count, picture_black_ratio,
+ picref->pos, av_ts2str(picref->pts),
+ av_ts2timestr(blackdetect->black_start, &inlink->time_base),
+ av_get_picture_type_char(picref->video->pict_type));
+
+ if (picture_black_ratio >= blackdetect->picture_black_ratio_th) {
+ if (!blackdetect->black_started) {
+ /* black starts here */
+ blackdetect->black_started = 1;
+ blackdetect->black_start = picref->pts;
+ }
+ } else if (blackdetect->black_started) {
+ /* black ends here */
+ blackdetect->black_started = 0;
+ blackdetect->black_end = picref->pts;
+
+ if ((blackdetect->black_end - blackdetect->black_start) >= blackdetect->min_black_duration) {
+ av_log(blackdetect, AV_LOG_INFO,
+ "black_start:%s black_end:%s black_duration:%s\n",
+ av_ts2timestr(blackdetect->black_start, &inlink->time_base),
+ av_ts2timestr(blackdetect->black_end, &inlink->time_base),
+ av_ts2timestr(blackdetect->black_end - blackdetect->black_start, &inlink->time_base));
+ }
+ }
+
+ blackdetect->frame_count++;
+ blackdetect->nb_black_pixels = 0;
+ avfilter_end_frame(inlink->dst->outputs[0]);
+}
+
+AVFilter avfilter_vf_blackdetect = {
+ .name = "blackdetect",
+ .description = NULL_IF_CONFIG_SMALL("Detect frames that are (almost) black."),
+
+ .priv_size = sizeof(BlackDetectContext),
+ .init = init,
+ .query_formats = query_formats,
+
+ .inputs = (const AVFilterPad[]) {
+ { .name = "default",
+ .type = AVMEDIA_TYPE_VIDEO,
+ .config_props = config_input,
+ .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 = (const AVFilterPad[]) {
+ { .name = "default",
+ .type = AVMEDIA_TYPE_VIDEO },
+ { .name = NULL }
+ },
+};
--
1.7.5.4
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