Extend the slice filter to make it issue slice height values randomly

[libav.git] / libavfilter / vf_slicify.c

diff --git a/libavfilter/vf_slicify.c b/libavfilter/vf_slicify.c
index 40824ce..e2ac594 100644 (file)
--- a/libavfilter/vf_slicify.c
+++ b/libavfilter/vf_slicify.c
@@ -24,10 +24,13 @@
  */
 
 #include "avfilter.h"
+#include "libavutil/pixdesc.h"
 
 typedef struct {
     int h;          ///< output slice height
     int vshift;     ///< vertical chroma subsampling shift
+    uint32_t lcg_state; ///< LCG state used to compute random slice height
+    int use_random_h;   ///< enable the use of random slice height values
 } SliceContext;
 
 static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
@@ -35,24 +38,21 @@ static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
     SliceContext *slice = ctx->priv;
 
     slice->h = 16;
-    if (args)
-        sscanf(args, "%d", &slice->h);
-
+    if (args) {
+        if (!strcmp(args, "random")) {
+            slice->use_random_h = 1;
+        } else {
+            sscanf(args, "%d", &slice->h);
+        }
+    }
     return 0;
 }
 
 static int config_props(AVFilterLink *link)
 {
     SliceContext *slice = link->dst->priv;
-    int tmp;
-
-    avcodec_get_chroma_sub_sample(link->format, &tmp, &slice->vshift);
-
-    /* ensure that slices play nice with chroma subsampling, and enforce
-     * a reasonable minimum size for the slices */
-    slice->h = FFMAX(8, slice->h & (-1 << slice->vshift));
 
-    av_log(link->dst, AV_LOG_INFO, "h:%d\n", slice->h);
+    slice->vshift = av_pix_fmt_descriptors[link->format].log2_chroma_h;
 
     return 0;
 }
@@ -65,6 +65,19 @@ static AVFilterPicRef *get_video_buffer(AVFilterLink *link, int perms,
 
 static void start_frame(AVFilterLink *link, AVFilterPicRef *picref)
 {
+    SliceContext *slice = link->dst->priv;
+
+    if (slice->use_random_h) {
+        slice->lcg_state = slice->lcg_state * 1664525 + 1013904223;
+        slice->h = 8 + (uint64_t)slice->lcg_state * 25 / UINT32_MAX;
+    }
+
+    /* ensure that slices play nice with chroma subsampling, and enforce
+     * a reasonable minimum size for the slices */
+    slice->h = FFMAX(8, slice->h & (-1 << slice->vshift));
+
+    av_log(link->dst, AV_LOG_DEBUG, "h:%d\n", slice->h);
+
     avfilter_start_frame(link->dst->outputs[0], picref);
 }
 
@@ -73,16 +86,24 @@ static void end_frame(AVFilterLink *link)
     avfilter_end_frame(link->dst->outputs[0]);
 }
 
-static void draw_slice(AVFilterLink *link, int y, int h)
+static void draw_slice(AVFilterLink *link, int y, int h, int slice_dir)
 {
     SliceContext *slice = link->dst->priv;
     int y2;
 
-    for (y2 = y; y2 + slice->h <= y + h; y2 += slice->h)
-        avfilter_draw_slice(link->dst->outputs[0], y2, slice->h);
+    if (slice_dir == 1) {
+        for (y2 = y; y2 + slice->h <= y + h; y2 += slice->h)
+            avfilter_draw_slice(link->dst->outputs[0], y2, slice->h, slice_dir);
+
+        if (y2 < y + h)
+            avfilter_draw_slice(link->dst->outputs[0], y2, y + h - y2, slice_dir);
+    } else if (slice_dir == -1) {
+        for (y2 = y + h; y2 - slice->h >= y; y2 -= slice->h)
+            avfilter_draw_slice(link->dst->outputs[0], y2 - slice->h, slice->h, slice_dir);
 
-    if (y2 < y + h)
-        avfilter_draw_slice(link->dst->outputs[0], y2, y + h - y2);
+        if (y2 > y)
+            avfilter_draw_slice(link->dst->outputs[0], y, y2 - y, slice_dir);
+    }
 }
 
 AVFilter avfilter_vf_slicify = {