avfilter/vf_mix: use time_base from framesync

libavfilter/vf_mix.c

@@ -217,7 +217,6 @@ static int config_output(AVFilterLink *outlink)
 {
     AVFilterContext *ctx = outlink->src;
     MixContext *s = ctx->priv;
-    AVRational time_base = ctx->inputs[0]->time_base;
     AVRational frame_rate = ctx->inputs[0]->frame_rate;
     AVFilterLink *inlink = ctx->inputs[0];
     int height = ctx->inputs[0]->h;
@@ -252,7 +251,6 @@ static int config_output(AVFilterLink *outlink)
 
     outlink->w          = width;
     outlink->h          = height;
-    outlink->time_base  = time_base;
     outlink->frame_rate = frame_rate;
 
     if ((ret = ff_framesync_init(&s->fs, ctx, s->nb_inputs)) < 0)
@@ -271,7 +269,10 @@ static int config_output(AVFilterLink *outlink)
         in[i].after  = (s->duration == 1 || (s->duration == 2 && i == 0)) ? EXT_STOP : EXT_INFINITY;
     }
 
-    return ff_framesync_configure(&s->fs);
+    ret = ff_framesync_configure(&s->fs);
+    outlink->time_base = s->fs.time_base;
+
+    return ret;
 }
 
 static av_cold void uninit(AVFilterContext *ctx)