avfilter/vf_maskedmerge: fix bug when copying >8bit plane(s)

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavfilter/maskedmerge.h

@@ -27,6 +27,7 @@
 typedef struct MaskedMergeContext {
     const AVClass *class;
     int width[4], height[4];
+    int linesize[4];
     int nb_planes;
     int planes;
     int half, depth;

libavfilter/vf_maskedmerge.c

@@ -91,7 +91,7 @@ static int process_frame(FFFrameSync *fs)
         for (p = 0; p < s->nb_planes; p++) {
             if (!((1 << p) & s->planes)) {
                 av_image_copy_plane(out->data[p], out->linesize[p], base->data[p], base->linesize[p],
-                                    s->width[p], s->height[p]);
+                                    s->linesize[p], s->height[p]);
                 continue;
             }
 
@@ -229,6 +229,9 @@ static int config_output(AVFilterLink *outlink)
     outlink->sample_aspect_ratio = base->sample_aspect_ratio;
     outlink->frame_rate = base->frame_rate;
 
+    if ((ret = av_image_fill_linesizes(s->linesize, outlink->format, outlink->w)) < 0)
+        return ret;
+
     if ((ret = ff_framesync_init(&s->fs, ctx, 3)) < 0)
         return ret;