avfilter/avf_a3dscope,avf_showcwt: set video frame duration

libavfilter/avf_a3dscope.c

@@ -243,6 +243,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
     for (int y = 0; y < outlink->h; y++)
         memset(out->data[0] + y * out->linesize[0], 0, outlink->w * 4);
     out->pts = av_rescale_q(in->pts, inlink->time_base, outlink->time_base);
+    out->duration = 1;
 
     projection_matrix(s->fov, half_width / half_height, 0.1f, 1000000.f, s->projection_matrix);
     view_matrix(s->eye, s->zoom, s->roll, s->pitch, s->yaw, s->view_matrix);

libavfilter/avf_showcwt.c

@@ -869,6 +869,7 @@ static int output_frame(AVFilterContext *ctx)
         int64_t pts_offset = s->new_frame ? 0LL : av_rescale(s->ihop_index, s->hop_size, s->ihop_size);
 
         s->outpicref->pts = av_rescale_q(s->in_pts + pts_offset, inlink->time_base, outlink->time_base);
+        s->outpicref->duration = 1;
     }
 
     s->ihop_index++;