vsrc_buffer: Reinit scale filter when an existing filter is used.

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

libavfilter/vsrc_buffer.c

@@ -84,6 +84,8 @@ int av_vsrc_buffer_add_frame2(AVFilterContext *buffer_filter, AVFrame *frame,
             scale->outputs[0]->time_base = scale->inputs[0]->time_base;
 
             scale->outputs[0]->format= c->pix_fmt;
+        } else if(!strcmp(scale->filter->name, "scale")) {
+            scale->filter->init(scale, c->sws_param, NULL);
         }
 
         c->pix_fmt= scale->inputs[0]->format= pix_fmt;