Index: libmpdemux/demux_mpg.c
===================================================================
--- libmpdemux/demux_mpg.c	£¨ÐÞ¶©°æ 22356£©
+++ libmpdemux/demux_mpg.c	£¨¹¤×÷¿½±´£©
@@ -180,7 +180,8 @@
 
     //if seeking is allowed set has_valid_timestamps if appropriate
     if(demuxer->seekable
-       && demuxer->stream->type == STREAMTYPE_FILE 
+       && (demuxer->stream->type == STREAMTYPE_FILE ||
+           demuxer->stream->type == STREAMTYPE_VCD)
        && demuxer->movi_start != demuxer-> movi_end
     )
     {
@@ -195,7 +196,7 @@
       float first_pts = read_first_mpeg_pts_at_position(demuxer, demuxer->movi_start);
       if(first_pts != -1.0)
       {
-        float middle_pts = read_first_mpeg_pts_at_position(demuxer, (demuxer->movi_end - demuxer->movi_start)/2);
+        float middle_pts = read_first_mpeg_pts_at_position(demuxer, (demuxer->movi_end + demuxer->movi_start)/2);
         if(middle_pts != -1.0)
         {
           float final_pts = read_first_mpeg_pts_at_position(demuxer, demuxer->movi_end - TIMESTAMP_PROBE_LEN);