Implement cropdetect filter.

Originally committed as revision 25447 to svn://svn.ffmpeg.org/ffmpeg/trunk

Changelog

@@ -45,6 +45,7 @@ version <next>:
 - Demuxer for Leitch/Harris' VR native stream format (LXF)
 - RTP depacketization of the X-QT QuickTime format
 - SAP (Session Announcement Protocol, RFC 2974) muxer
+- cropdetect filter
 
 
 version 0.6:

configure

@@ -1399,6 +1399,7 @@ udp_protocol_deps="network"
 
 # filters
 blackframe_filter_deps="gpl"
+cropdetect_filter_deps="gpl"
 frei0r_filter_deps="frei0r dlopen strtok_r"
 ocv_smooth_filter_deps="libopencv"
 yadif_filter_deps="gpl"

doc/filters.texi

@@ -190,6 +190,41 @@ crop=in_w-100:in_h-100:100:100
 "crop=in_w/2:in_h/2:y:10+10*sin(n/10)"
 @end example
 
+@section cropdetect
+
+Auto-detect crop size.
+
+Calculate necessary cropping parameters and prints the recommended
+parameters through the logging system. The detected dimensions
+correspond to the non-black area of the input video.
+
+It accepts the syntax:
+@example
+cropdetect[=@var{limit}:@var{round}[:@var{reset}]]
+@end example
+
+@table @option
+
+@item limit
+Threshold, which can be optionally specified from nothing (0) to
+everything (255), defaults to 24.
+
+@item round
+Value which the width/height should be divisible by, defaults to
+16. The offset is automatically adjusted to center the video. Use 2 to
+get only even dimensions (needed for 4:2:2 video). 16 is best when
+encoding to most video codecs.
+
+@item reset
+Counter that determines after how many frames cropdetect will reset
+the previously detected largest video area and start over to detect
+the current optimal crop area. Defaults to 0.
+
+This can be useful when channel logos distort the video area. 0
+indicates never reset and return the largest area encountered during
+playback.
+@end table
+
 @section drawbox
 
 Draw a colored box on the input image.

libavfilter/Makefile

@@ -23,6 +23,7 @@ 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-$(CONFIG_CROPDETECT_FILTER)             += vf_cropdetect.o
 OBJS-$(CONFIG_DRAWBOX_FILTER)                += vf_drawbox.o
 OBJS-$(CONFIG_FIFO_FILTER)                   += vf_fifo.o
 OBJS-$(CONFIG_FORMAT_FILTER)                 += vf_format.o

libavfilter/allfilters.c

@@ -43,6 +43,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER (ASPECT,      aspect,      vf);
     REGISTER_FILTER (BLACKFRAME,  blackframe,  vf);
     REGISTER_FILTER (CROP,        crop,        vf);
+    REGISTER_FILTER (CROPDETECT,  cropdetect,  vf);
     REGISTER_FILTER (DRAWBOX,     drawbox,     vf);
     REGISTER_FILTER (FIFO,        fifo,        vf);
     REGISTER_FILTER (FORMAT,      format,      vf);

libavfilter/avfilter.h

@@ -25,8 +25,8 @@
 #include "libavutil/avutil.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  1
-#define LIBAVFILTER_VERSION_MINOR 50
-#define LIBAVFILTER_VERSION_MICRO  1
+#define LIBAVFILTER_VERSION_MINOR 51
+#define LIBAVFILTER_VERSION_MICRO  0
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \

libavfilter/vf_cropdetect.c

@@ -0,0 +1,214 @@
+/*
+ * Copyright (C) 2002 A'rpi
+ * 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
+ * border detection filter
+ * Ported from MPlayer libmpcodecs/vf_cropdetect.c.
+ */
+
+#include "libavcore/imgutils.h"
+#include "avfilter.h"
+
+typedef struct {
+    int x1, y1, x2, y2;
+    int limit;
+    int round;
+    int reset_count;
+    int frame_nb;
+    int max_pixsteps[4];
+} CropDetectContext;
+
+static int query_formats(AVFilterContext *ctx)
+{
+    static const enum PixelFormat pix_fmts[] = {
+        PIX_FMT_YUV420P, PIX_FMT_YUVJ420P,
+        PIX_FMT_YUV422P, PIX_FMT_YUVJ422P,
+        PIX_FMT_YUV444P, PIX_FMT_YUVJ444P,
+        PIX_FMT_YUV411P, PIX_FMT_GRAY8,
+        PIX_FMT_NV12,    PIX_FMT_NV21,
+        PIX_FMT_NONE
+    };
+
+    avfilter_set_common_formats(ctx, avfilter_make_format_list(pix_fmts));
+    return 0;
+}
+
+static int checkline(void *ctx, const unsigned char *src, int stride, int len, int bpp)
+{
+    int total = 0;
+    int div = len;
+
+    switch (bpp) {
+    case 1:
+        while (--len >= 0) {
+            total += src[0];
+            src += stride;
+        }
+        break;
+    case 3:
+    case 4:
+        while (--len >= 0) {
+            total += src[0] + src[1] + src[2];
+            src += stride;
+        }
+        div *= 3;
+        break;
+    }
+    total /= div;
+
+    av_log(ctx, AV_LOG_DEBUG, "total:%d\n", total);
+    return total;
+}
+
+static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
+{
+    CropDetectContext *cd = ctx->priv;
+
+    cd->limit = 24;
+    cd->round = 0;
+    cd->reset_count = 0;
+    cd->frame_nb = -2;
+
+    if (args)
+        sscanf(args, "%d:%d:%d", &cd->limit, &cd->round, &cd->reset_count);
+
+    av_log(ctx, AV_LOG_INFO, "limit:%d round:%d reset_count:%d\n",
+           cd->limit, cd->round, cd->reset_count);
+
+    return 0;
+}
+
+static int config_input(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    CropDetectContext *cd = ctx->priv;
+
+    av_image_fill_max_pixsteps(cd->max_pixsteps, NULL,
+                               &av_pix_fmt_descriptors[inlink->format]);
+
+    cd->x1 = inlink->w - 1;
+    cd->y1 = inlink->h - 1;
+    cd->x2 = 0;
+    cd->y2 = 0;
+
+    return 0;
+}
+
+static void end_frame(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    CropDetectContext *cd = ctx->priv;
+    AVFilterBufferRef *picref = inlink->cur_buf;
+    int bpp = cd->max_pixsteps[0];
+    int w, h, x, y, shrink_by;
+
+    // ignore first 2 frames - they may be empty
+    if (++cd->frame_nb > 0) {
+        // Reset the crop area every reset_count frames, if reset_count is > 0
+        if (cd->reset_count > 0 && cd->frame_nb > cd->reset_count) {
+            cd->x1 = picref->video->w-1;
+            cd->y1 = picref->video->h-1;
+            cd->x2 = 0;
+            cd->y2 = 0;
+            cd->frame_nb = 1;
+        }
+
+        for (y = 0; y < cd->y1; y++) {
+            if (checkline(ctx, picref->data[0] + picref->linesize[0] * y, bpp, picref->video->w, bpp) > cd->limit) {
+                cd->y1 = y;
+                break;
+            }
+        }
+
+        for (y = picref->video->h-1; y > cd->y2; y--) {
+            if (checkline(ctx, picref->data[0] + picref->linesize[0] * y, bpp, picref->video->w, bpp) > cd->limit) {
+                cd->y2 = y;
+                break;
+            }
+        }
+
+        for (y = 0; y < cd->x1; y++) {
+            if (checkline(ctx, picref->data[0] + bpp*y, picref->linesize[0], picref->video->h, bpp) > cd->limit) {
+                cd->x1 = y;
+                break;
+            }
+        }
+
+        for (y = picref->video->w-1; y > cd->x2; y--) {
+            if (checkline(ctx, picref->data[0] + bpp*y, picref->linesize[0], picref->video->h, bpp) > cd->limit) {
+                cd->x2 = y;
+                break;
+            }
+        }
+
+        // round x and y (up), important for yuv colorspaces
+        // make sure they stay rounded!
+        x = (cd->x1+1) & ~1;
+        y = (cd->y1+1) & ~1;
+
+        w = cd->x2 - x + 1;
+        h = cd->y2 - y + 1;
+
+        // w and h must be divisible by 2 as well because of yuv
+        // colorspace problems.
+        if (cd->round <= 1)
+            cd->round = 16;
+        if (cd->round % 2)
+            cd->round *= 2;
+
+        shrink_by = w % cd->round;
+        w -= shrink_by;
+        x += (shrink_by/2 + 1) & ~1;
+
+        shrink_by = h % cd->round;
+        h -= shrink_by;
+        y += (shrink_by/2 + 1) & ~1;
+
+        av_log(ctx, AV_LOG_INFO,
+               "x1:%d x2:%d y1:%d y2:%d w:%d h:%d x:%d y:%d pos:%"PRId64" pts:%f crop=%d:%d:%d:%d\n",
+               cd->x1, cd->x2, cd->y1, cd->y2, w, h, x, y, picref->pos,
+               picref->pts == AV_NOPTS_VALUE ? -1 : (double)picref->pts / AV_TIME_BASE,
+               w, h, x, y);
+    }
+
+    avfilter_end_frame(inlink->dst->outputs[0]);
+}
+
+AVFilter avfilter_vf_cropdetect = {
+    .name        = "cropdetect",
+    .description = NULL_IF_CONFIG_SMALL("Auto-detect crop size."),
+
+    .priv_size = sizeof(CropDetectContext),
+    .init      = init,
+
+    .query_formats = query_formats,
+
+    .inputs    = (AVFilterPad[]) {{ .name = "default",
+                                    .type             = AVMEDIA_TYPE_VIDEO,
+                                    .config_props     = config_input,
+                                    .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}},
+};