always handle negative timestamp differences as timestamp discontinuity

Originally committed as revision 9984 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffmpeg.c

@@ -1922,8 +1922,9 @@ static int av_encode(AVFormatContext **output_files,
 
 //        fprintf(stderr, "next:%"PRId64" dts:%"PRId64" off:%"PRId64" %d\n", ist->next_pts, pkt.dts, input_files_ts_offset[ist->file_index], ist->st->codec->codec_type);
         if (pkt.dts != AV_NOPTS_VALUE && ist->next_pts != AV_NOPTS_VALUE) {
-            int64_t delta= av_rescale_q(pkt.dts, ist->st->time_base, AV_TIME_BASE_Q) - ist->next_pts;
-            if(FFABS(delta) > 1LL*dts_delta_threshold*AV_TIME_BASE && !copy_ts){
+            int64_t pkt_dts= av_rescale_q(pkt.dts, ist->st->time_base, AV_TIME_BASE_Q);
+            int64_t delta= pkt_dts - ist->next_pts;
+            if((FFABS(delta) > 1LL*dts_delta_threshold*AV_TIME_BASE || pkt_dts+1<ist->pts)&& !copy_ts){
                 input_files_ts_offset[ist->file_index]-= delta;
                 if (verbose > 2)
                     fprintf(stderr, "timestamp discontinuity %"PRId64", new offset= %"PRId64"\n", delta, input_files_ts_offset[ist->file_index]);