vsrc_mandelbrot: switch to filter_frame

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/vsrc_mandelbrot.c

@@ -387,11 +387,8 @@ static int request_frame(AVFilterLink *link)
     picref->pts = mb->pts++;
     picref->pos = -1;
 
-    ff_start_frame(link, avfilter_ref_buffer(picref, ~0));
     draw_mandelbrot(link->src, (uint32_t*)picref->data[0], picref->linesize[0]/4, picref->pts);
-    ff_draw_slice(link, 0, mb->h, 1);
-    ff_end_frame(link);
-    avfilter_unref_buffer(picref);
+    ff_filter_frame(link, picref);
 
     return 0;
 }