lavfi/cropdetect: Add new mode to detect crop-area based on motion vectors and edges

This filter allows crop detection even if the video is embedded in non-black areas.

2 files changed, 211 insertions, 2 deletions

diff --git a/libavfilter/version.h b/libavfilter/version.h
index 0946ee91e8..19a009c110 100644
--- a/libavfilter/version.h
+++ b/libavfilter/version.h
@@ -32,7 +32,7 @@
 #include "version_major.h"
 
 #define LIBAVFILTER_VERSION_MINOR  46
-#define LIBAVFILTER_VERSION_MICRO 100
+#define LIBAVFILTER_VERSION_MICRO 101
 
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
diff --git a/libavfilter/vf_cropdetect.c b/libavfilter/vf_cropdetect.c
index b887b9ecb1..e920e671ab 100644
--- a/libavfilter/vf_cropdetect.c
+++ b/libavfilter/vf_cropdetect.c
@@ -26,11 +26,14 @@
 #include "libavutil/imgutils.h"
 #include "libavutil/internal.h"
 #include "libavutil/opt.h"
+#include "libavutil/motion_vector.h"
+#include "libavutil/qsort.h"
 
 #include "avfilter.h"
 #include "formats.h"
 #include "internal.h"
 #include "video.h"
+#include "edge_common.h"
 
 typedef struct CropDetectContext {
     const AVClass *class;
@@ -42,6 +45,16 @@ typedef struct CropDetectContext {
     int frame_nb;
     int max_pixsteps[4];
     int max_outliers;
+    int mode;
+    int window_size;
+    int mv_threshold;
+    float   low, high;
+    uint8_t low_u8, high_u8;
+    uint8_t  *filterbuf;
+    uint8_t  *tmpbuf;
+    uint16_t *gradients;
+    char     *directions;
+    int      *bboxes[4];
 } CropDetectContext;
 
 static const enum AVPixelFormat pix_fmts[] = {
@@ -61,6 +74,17 @@ static const enum AVPixelFormat pix_fmts[] = {
     AV_PIX_FMT_NONE
 };
 
+enum CropMode {
+    MODE_BLACK,
+    MODE_MV_EDGES,
+    MODE_NB
+};
+
+static int comp(const int *a,const int *b)
+{
+    return FFDIFFSIGN(*a, *b);
+}
+
 static int checkline(void *ctx, const unsigned char *src, int stride, int len, int bpp)
 {
     int total = 0;
@@ -116,11 +140,43 @@ static int checkline(void *ctx, const unsigned char *src, int stride, int len, i
     return total;
 }
 
+static int checkline_edge(void *ctx, const unsigned char *src, int stride, int len, int bpp)
+{
+    const uint16_t *src16 = (const uint16_t *)src;
+
+    switch (bpp) {
+    case 1:
+        while (--len >= 0) {
+            if (src[0]) return 0;
+            src += stride;
+        }
+        break;
+    case 2:
+        stride >>= 1;
+        while (--len >= 0) {
+            if (src16[0]) return 0;
+            src16 += stride;
+        }
+        break;
+    case 3:
+    case 4:
+        while (--len >= 0) {
+            if (src[0] || src[1] || src[2]) return 0;
+            src += stride;
+        }
+        break;
+    }
+
+    return 1;
+}
+
 static av_cold int init(AVFilterContext *ctx)
 {
     CropDetectContext *s = ctx->priv;
 
     s->frame_nb = -1 * s->skip;
+    s->low_u8   = s->low  * 255. + .5;
+    s->high_u8  = s->high * 255. + .5;
 
     av_log(ctx, AV_LOG_VERBOSE, "limit:%f round:%d skip:%d reset_count:%d\n",
            s->limit, s->round, s->skip, s->reset_count);
@@ -128,11 +184,27 @@ static av_cold int init(AVFilterContext *ctx)
     return 0;
 }
 
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    CropDetectContext *s = ctx->priv;
+
+    av_freep(&s->tmpbuf);
+    av_freep(&s->filterbuf);
+    av_freep(&s->gradients);
+    av_freep(&s->directions);
+    av_freep(&s->bboxes[0]);
+    av_freep(&s->bboxes[1]);
+    av_freep(&s->bboxes[2]);
+    av_freep(&s->bboxes[3]);
+}
+
 static int config_input(AVFilterLink *inlink)
 {
     AVFilterContext *ctx = inlink->dst;
     CropDetectContext *s = ctx->priv;
     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
+    const int bufsize = inlink->w * inlink->h;
+    int bpp;
 
     av_image_fill_max_pixsteps(s->max_pixsteps, NULL, desc);
 
@@ -144,6 +216,21 @@ static int config_input(AVFilterLink *inlink)
     s->x2 = 0;
     s->y2 = 0;
 
+    bpp            = s->max_pixsteps[0];
+    s->window_size = FFMAX(s->reset_count, 15);
+    s->tmpbuf      = av_malloc(bufsize);
+    s->filterbuf   = av_malloc(bufsize * s->max_pixsteps[0]);
+    s->gradients   = av_calloc(bufsize, sizeof(*s->gradients));
+    s->directions  = av_malloc(bufsize);
+    s->bboxes[0]   = av_malloc(s->window_size * sizeof(*s->bboxes[0]));
+    s->bboxes[1]   = av_malloc(s->window_size * sizeof(*s->bboxes[1]));
+    s->bboxes[2]   = av_malloc(s->window_size * sizeof(*s->bboxes[2]));
+    s->bboxes[3]   = av_malloc(s->window_size * sizeof(*s->bboxes[3]));
+
+    if (!s->tmpbuf    || !s->filterbuf || !s->gradients || !s->directions ||
+        !s->bboxes[0] || !s->bboxes[1] || !s->bboxes[2] || !s->bboxes[3])
+        return AVERROR(ENOMEM);
+
     return 0;
 }
 
@@ -155,11 +242,28 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
     AVFilterContext *ctx = inlink->dst;
     CropDetectContext *s = ctx->priv;
     int bpp = s->max_pixsteps[0];
-    int w, h, x, y, shrink_by;
+    int w, h, x, y, shrink_by, i;
     AVDictionary **metadata;
     int outliers, last_y;
     int limit = lrint(s->limit);
 
+    const int inw = inlink->w;
+    const int inh = inlink->h;
+    uint8_t *tmpbuf     = s->tmpbuf;
+    uint8_t *filterbuf  = s->filterbuf;
+    uint16_t *gradients = s->gradients;
+    int8_t *directions  = s->directions;
+    const AVFrameSideData *sd = NULL;
+    int scan_w, scan_h, bboff;
+
+    void (*sobel)(int w, int h, uint16_t *dst, int dst_linesize,
+                  int8_t *dir, int dir_linesize,
+                  const uint8_t *src, int src_linesize, int src_stride) = (bpp == 2) ? &ff_sobel_16 : &ff_sobel_8;
+    void (*gaussian_blur)(int w, int h,
+                          uint8_t *dst, int dst_linesize,
+                          const uint8_t *src, int src_linesize, int src_stride) = (bpp == 2) ? &ff_gaussian_blur_16 : &ff_gaussian_blur_8;
+
+
     // ignore first s->skip frames
     if (++s->frame_nb > 0) {
         metadata = &frame->metadata;
@@ -185,11 +289,109 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
                 last_y = y INC;\
         }
 
+        if (s->mode == MODE_BLACK) {
         FIND(s->y1,                 0,               y < s->y1, +1, frame->linesize[0], bpp, frame->width);
         FIND(s->y2, frame->height - 1, y > FFMAX(s->y2, s->y1), -1, frame->linesize[0], bpp, frame->width);
         FIND(s->x1,                 0,               y < s->x1, +1, bpp, frame->linesize[0], frame->height);
         FIND(s->x2,  frame->width - 1, y > FFMAX(s->x2, s->x1), -1, bpp, frame->linesize[0], frame->height);
+        } else { // MODE_MV_EDGES
+            sd = av_frame_get_side_data(frame, AV_FRAME_DATA_MOTION_VECTORS);
+            s->x1 = 0;
+            s->y1 = 0;
+            s->x2 = inw - 1;
+            s->y2 = inh - 1;
+
+            if (!sd) {
+                av_log(ctx, AV_LOG_WARNING, "Cannot detect: no motion vectors available");
+            } else {
+                // gaussian filter to reduce noise
+                gaussian_blur(inw, inh,
+                              filterbuf,  inw*bpp,
+                              frame->data[0], frame->linesize[0], bpp);
+
+                // compute the 16-bits gradients and directions for the next step
+                sobel(inw, inh, gradients, inw, directions, inw, filterbuf, inw*bpp, bpp);
+
+                // non_maximum_suppression() will actually keep & clip what's necessary and
+                // ignore the rest, so we need a clean output buffer
+                memset(tmpbuf, 0, inw * inh);
+                ff_non_maximum_suppression(inw, inh, tmpbuf, inw, directions, inw, gradients, inw);
+
+
+                // keep high values, or low values surrounded by high values
+                ff_double_threshold(s->low_u8, s->high_u8, inw, inh,
+                                    tmpbuf, inw, tmpbuf, inw);
+
+                // scan all MVs and store bounding box
+                s->x1 = inw - 1;
+                s->y1 = inh - 1;
+                s->x2 = 0;
+                s->y2 = 0;
+                for (i = 0; i < sd->size / sizeof(AVMotionVector); i++) {
+                    const AVMotionVector *mv = (const AVMotionVector*)sd->data + i;
+                    const int mx = mv->dst_x - mv->src_x;
+                    const int my = mv->dst_y - mv->src_y;
+
+                    if (mv->dst_x >= 0 && mv->dst_x < inw &&
+                        mv->dst_y >= 0 && mv->dst_y < inh &&
+                        mv->src_x >= 0 && mv->src_x < inw &&
+                        mv->src_y >= 0 && mv->src_y < inh &&
+                        mx * mx + my * my >= s->mv_threshold * s->mv_threshold) {
+                        s->x1 = mv->dst_x < s->x1 ? mv->dst_x : s->x1;
+                        s->y1 = mv->dst_y < s->y1 ? mv->dst_y : s->y1;
+                        s->x2 = mv->dst_x > s->x2 ? mv->dst_x : s->x2;
+                        s->y2 = mv->dst_y > s->y2 ? mv->dst_y : s->y2;
+                    }
+                }
+
+                // assert x1<x2, y1<y2
+                if (s->x1 > s->x2) FFSWAP(int, s->x1, s->x2);
+                if (s->y1 > s->y2) FFSWAP(int, s->y1, s->y2);
+
+                // scan outward looking for 0-edge-lines in edge image
+                scan_w = s->x2 - s->x1;
+                scan_h = s->y2 - s->y1;
+
+#define FIND_EDGE(DST, FROM, NOEND, INC, STEP0, STEP1, LEN)             \
+    for (last_y = y = FROM; NOEND; y = y INC) {                         \
+        if (checkline_edge(ctx, tmpbuf + STEP0 * y, STEP1, LEN, bpp)) { \
+            if (last_y INC == y) {                                      \
+                DST = y;                                                \
+                break;                                                  \
+            } else                                                      \
+                last_y = y;                                             \
+        }                                                               \
+    }                                                                   \
+    if (!(NOEND)) {                                                     \
+        DST = y -(INC);                                                 \
+    }
 
+                FIND_EDGE(s->y1, s->y1, y >=  0, -1, inw, bpp, scan_w);
+                FIND_EDGE(s->y2, s->y2, y < inh, +1, inw, bpp, scan_w);
+                FIND_EDGE(s->x1, s->x1, y >=  0, -1, bpp, inw, scan_h);
+                FIND_EDGE(s->x2, s->x2, y < inw, +1, bpp, inw, scan_h);
+
+                // queue bboxes
+                bboff = (s->frame_nb - 1) % s->window_size;
+                s->bboxes[0][bboff] = s->x1;
+                s->bboxes[1][bboff] = s->x2;
+                s->bboxes[2][bboff] = s->y1;
+                s->bboxes[3][bboff] = s->y2;
+
+                // sort queue
+                bboff = FFMIN(s->frame_nb, s->window_size);
+                AV_QSORT(s->bboxes[0], bboff, int, comp);
+                AV_QSORT(s->bboxes[1], bboff, int, comp);
+                AV_QSORT(s->bboxes[2], bboff, int, comp);
+                AV_QSORT(s->bboxes[3], bboff, int, comp);
+
+                // return median of window_size elems
+                s->x1 = s->bboxes[0][bboff/2];
+                s->x2 = s->bboxes[1][bboff/2];
+                s->y1 = s->bboxes[2][bboff/2];
+                s->y2 = s->bboxes[3][bboff/2];
+            }
+        }
 
         // round x and y (up), important for yuv colorspaces
         // make sure they stay rounded!
@@ -243,6 +445,12 @@ static const AVOption cropdetect_options[] = {
     { "skip",  "Number of initial frames to skip",                    OFFSET(skip),        AV_OPT_TYPE_INT, { .i64 = 2 },  0, INT_MAX, FLAGS },
     { "reset_count", "Recalculate the crop area after this many frames",OFFSET(reset_count),AV_OPT_TYPE_INT,{ .i64 = 0 },  0, INT_MAX, FLAGS },
     { "max_outliers", "Threshold count of outliers",                  OFFSET(max_outliers),AV_OPT_TYPE_INT, { .i64 = 0 },  0, INT_MAX, FLAGS },
+    { "mode", "set mode", OFFSET(mode), AV_OPT_TYPE_INT, {.i64=MODE_BLACK}, 0, MODE_NB-1, FLAGS, "mode" },
+        { "black",    "detect black pixels surrounding the video",     0, AV_OPT_TYPE_CONST, {.i64=MODE_BLACK},    INT_MIN, INT_MAX, FLAGS, "mode" },
+        { "mvedges",  "detect motion and edged surrounding the video", 0, AV_OPT_TYPE_CONST, {.i64=MODE_MV_EDGES}, INT_MIN, INT_MAX, FLAGS, "mode" },
+    { "high", "Set high threshold for edge detection",                OFFSET(high),        AV_OPT_TYPE_FLOAT, {.dbl=25/255.}, 0, 1, FLAGS },
+    { "low", "Set low threshold for edge detection",                  OFFSET(low),         AV_OPT_TYPE_FLOAT, {.dbl=15/255.}, 0, 1, FLAGS },
+    { "mv_threshold", "motion vector threshold when estimating video window size", OFFSET(mv_threshold), AV_OPT_TYPE_INT, {.i64=8}, 0, 100, FLAGS},
     { NULL }
 };
 
@@ -270,6 +478,7 @@ const AVFilter ff_vf_cropdetect = {
     .priv_size     = sizeof(CropDetectContext),
     .priv_class    = &cropdetect_class,
     .init          = init,
+    .uninit        = uninit,
     FILTER_INPUTS(avfilter_vf_cropdetect_inputs),
     FILTER_OUTPUTS(avfilter_vf_cropdetect_outputs),
     FILTER_PIXFMTS_ARRAY(pix_fmts),