libavfilter/vf_pad.c:266: error: Integer Overflow L2
  ([0, +oo] - 1):unsigned32 by call to `avfilter_unref_buffer`.

libavfilter/vf_pad.c:266:5: Call
264. {
265.     avfilter_end_frame(link->dst->outputs[0]);
266.     avfilter_unref_buffer(link->cur_pic);
         ^
267. }
268. 

libavfilter/avfilter.c:57:1: <LHS trace>
55. }
56. 
57. void avfilter_unref_buffer(AVFilterBufferRef *ref)
    ^
58. {
59.     if(!(--ref->buf->refcount))

libavfilter/avfilter.c:57:1: Parameter `ref->buf->refcount`
  55. }
  56. 
  57. void avfilter_unref_buffer(AVFilterBufferRef *ref)
      ^
  58. {
  59.     if(!(--ref->buf->refcount))

libavfilter/avfilter.c:59:10: Binary operation: ([0, +oo] - 1):unsigned32 by call to `avfilter_unref_buffer` 
  57. void avfilter_unref_buffer(AVFilterBufferRef *ref)
  58. {
  59.     if(!(--ref->buf->refcount))
               ^
  60.         ref->buf->free(ref->buf);
  61.     av_free(ref);
