avformat: remove a workaround for broken timestamps

This modifies pts in situations other than what was intended, leading to
invalid timestamps.

Reverts commit 90bb394dcc

libavformat/utils.c

@@ -985,15 +985,6 @@ static void compute_pkt_fields(AVFormatContext *s, AVStream *st,
                 }
             }
 
-            if(pkt->pts != AV_NOPTS_VALUE && duration){
-                int64_t old_diff= FFABS(st->cur_dts - duration - pkt->pts);
-                int64_t new_diff= FFABS(st->cur_dts - pkt->pts);
-                if(old_diff < new_diff && old_diff < (duration>>3)){
-                    pkt->pts += duration;
-    //                av_log(NULL, AV_LOG_DEBUG, "id:%d old:%"PRId64" new:%"PRId64" dur:%d cur:%"PRId64" size:%d\n", pkt->stream_index, old_diff, new_diff, pkt->duration, st->cur_dts, pkt->size);
-                }
-            }
-
             /* presentation is not delayed : PTS and DTS are the same */
             if(pkt->pts == AV_NOPTS_VALUE)
                 pkt->pts = pkt->dts;