avfilter/vf_midequalizer: use time_base from framesync

Fixes non-monotonous timestamps.

libavfilter/vf_midequalizer.c

@@ -307,7 +307,6 @@ static int config_output(AVFilterLink *outlink)
 
     outlink->w = in0->w;
     outlink->h = in0->h;
-    outlink->time_base = in0->time_base;
     outlink->sample_aspect_ratio = in0->sample_aspect_ratio;
     outlink->frame_rate = in0->frame_rate;
 
@@ -326,7 +325,10 @@ static int config_output(AVFilterLink *outlink)
     s->fs.opaque   = s;
     s->fs.on_event = process_frame;
 
-    return ff_framesync_configure(&s->fs);
+    ret = ff_framesync_configure(&s->fs);
+    outlink->time_base = s->fs.time_base;
+
+    return ret;
 }
 
 static int activate(AVFilterContext *ctx)