vf_fps: Replace use of deprecated AVFilterBufferRef by AVFrame

libavfilter/vf_fps.c

@@ -103,7 +103,7 @@ static av_cold void uninit(AVFilterContext *ctx)
 {
     FPSContext *s = ctx->priv;
     if (s->fifo) {
-        s->drop += av_fifo_size(s->fifo) / sizeof(AVFilterBufferRef*);
+        s->drop += av_fifo_size(s->fifo) / sizeof(AVFrame*);
         flush_fifo(s->fifo);
         av_fifo_free(s->fifo);
     }