[FFmpeg-devel] [PATCH] Align overlaied video movie x/y and w/h sizes to chroma subsampling values.

[Stefano Sabatini]

Fix alignment bands when the input video size or position is not
chroma-aligned.
---
 libavfilter/vf_overlay.c |   21 ++++++++++++---------
 1 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/libavfilter/vf_overlay.c b/libavfilter/vf_overlay.c
index a170e81..5e73da2 100644
--- a/libavfilter/vf_overlay.c
+++ b/libavfilter/vf_overlay.c
@@ -58,7 +58,8 @@ enum var_name {
 #define OVERLAY 1
 
 typedef struct {
-    int x, y;                   ///< position of overlayed picture
+    int x, y;                   ///< chroma-aligned position of overlayed picture
+    int w, h;                   ///< chroma-aligned width and heigth of the overlaied video
 
     AVFilterBufferRef *overpicref;
 
@@ -129,31 +130,33 @@ static int config_input_overlay(AVFilterLink *inlink)
     var_values[VAR_PHI] = M_PHI;
     var_values[VAR_PI ] = M_PI;
 
+    over->w = ctx->inputs[OVERLAY]->w & ~((1 << over->hsub) - 1);
+    over->h = ctx->inputs[OVERLAY]->h & ~((1 << over->vsub) - 1);
+
     var_values[VAR_MAIN_W   ] = var_values[VAR_MW] = ctx->inputs[MAIN   ]->w;
     var_values[VAR_MAIN_H   ] = var_values[VAR_MH] = ctx->inputs[MAIN   ]->h;
-    var_values[VAR_OVERLAY_W] = var_values[VAR_OW] = ctx->inputs[OVERLAY]->w;
-    var_values[VAR_OVERLAY_H] = var_values[VAR_OH] = ctx->inputs[OVERLAY]->h;
+    var_values[VAR_OVERLAY_W] = var_values[VAR_OW] = over->w;
+    var_values[VAR_OVERLAY_H] = var_values[VAR_OH] = over->h;
 
     if ((ret = av_expr_parse_and_eval(&res, (expr = over->x_expr), var_names, var_values,
                                       NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0)
         goto fail;
-    over->x = res;
+    over->x = (int)res & ~((1 << over->hsub) - 1);
     if ((ret = av_expr_parse_and_eval(&res, (expr = over->y_expr), var_names, var_values,
                                       NULL, NULL, NULL, NULL, NULL, 0, ctx)))
         goto fail;
-    over->y = res;
+    over->y = (int)res & ~((1 << over->vsub) - 1);
     /* x may depend on y */
     if ((ret = av_expr_parse_and_eval(&res, (expr = over->x_expr), var_names, var_values,
                                       NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0)
         goto fail;
-    over->x = res;
+    over->x = (int)res & ~((1 << over->hsub) - 1);
 
     av_log(ctx, AV_LOG_INFO,
            "main w:%d h:%d fmt:%s overlay x:%d y:%d w:%d h:%d fmt:%s\n",
            ctx->inputs[MAIN]->w, ctx->inputs[MAIN]->h,
            av_pix_fmt_descriptors[ctx->inputs[MAIN]->format].name,
-           over->x, over->y,
-           ctx->inputs[OVERLAY]->w, ctx->inputs[OVERLAY]->h,
+           over->x, over->y, over->w, over->h,
            av_pix_fmt_descriptors[ctx->inputs[OVERLAY]->format].name);
 
     if (over->x < 0 || over->y < 0 ||
@@ -328,7 +331,7 @@ static void draw_slice(AVFilterLink *inlink, int y, int h, int slice_dir)
         !(over->x >= outpicref->video->w || over->y >= outpicref->video->h ||
           y+h < over->y || y >= over->y + over->overpicref->video->h)) {
         blend_slice(ctx, outpicref, over->overpicref, over->x, over->y,
-                    over->overpicref->video->w, over->overpicref->video->h,
+                    over->w, over->h,
                     y, outpicref->video->w, h);
     }
     avfilter_draw_slice(outlink, y, h, slice_dir);
-- 
1.7.2.3