vf_scale: apply the same transform to the aspect during init that is applied per frame

Signed-off-by: Anton Khirnov <anton@khirnov.net>

libavfilter/vf_scale.c

@@ -218,6 +218,14 @@ static int config_props(AVFilterLink *outlink)
     if (!scale->sws)
         return AVERROR(EINVAL);
 
+
+    if (inlink->sample_aspect_ratio.num)
+        outlink->sample_aspect_ratio = av_mul_q((AVRational){outlink->h*inlink->w,
+                                                             outlink->w*inlink->h},
+                                                inlink->sample_aspect_ratio);
+    else
+        outlink->sample_aspect_ratio = inlink->sample_aspect_ratio;
+
     return 0;
 
 fail: