Fix off by one offset with fetch_timestamps, pts_parser_problem.mpg.

Patch by Wolfram Gloger, wmglo at dentm dot med dot uni-muenchen dot de.

Originally committed as revision 18959 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mpeg12.c

@@ -2226,7 +2226,7 @@ int ff_mpeg1_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size,
                 }
             }
             if(s && state == PICTURE_START_CODE){
-                ff_fetch_timestamp(s, i-4, 1);
+                ff_fetch_timestamp(s, i-3, 1);
             }
         }
     }

tests/seek.regression.ref

@@ -3601,9 +3601,9 @@ ret: 0 st: 0 dts:0.660000 pts:0.700000 pos:564 size:24921 flags:1
 ret: 0 st:-1 ts:-1.000000 flags:0
 ret: 0 st: 0 dts:0.043533 pts:-102481911520608.625000 pos:29328 size:21852 flags:1
 ret: 0 st:-1 ts:1.894167 flags:1
-ret: 0 st: 0 dts:1.879533 pts:-102481911520608.625000 pos:-1 size:14260 flags:0
+ret: 0 st: 0 dts:0.780000 pts:0.820000 pos:65800 size:14260 flags:0
 ret: 0 st: 0 ts:0.788333 flags:0
-ret: 0 st: 0 dts:0.788733 pts:-102481911520608.625000 pos:-1 size:16309 flags:0
+ret: 0 st: 0 dts:0.700000 pts:0.740000 pos:29328 size:16309 flags:0
 ret: 0 st: 0 ts:-0.317500 flags:1
 ret: 0 st: 0 dts:0.027333 pts:-102481911520608.625000 pos:48504 size:21852 flags:1
 ret: 0 st: 1 ts:2.576667 flags:0
@@ -3621,7 +3621,7 @@ ret: 0 st: 0 dts:1.037133 pts:-102481911520608.625000 pos:82344 size:8888 flags:
 ret: 0 st: 1 ts:-0.058333 flags:0
 ret: 0 st: 0 dts:0.043533 pts:-102481911520608.625000 pos:48504 size:21852 flags:1
 ret: 0 st: 1 ts:2.835833 flags:1
-ret: 0 st: 0 dts:2.819133 pts:-102481911520608.625000 pos:-1 size:12495 flags:0
+ret: 0 st: 0 dts:0.860000 pts:0.900000 pos:98512 size:12495 flags:0
 ret: 0 st:-1 ts:1.730004 flags:0
 ret: 0 st: 0 dts:1.755333 pts:-102481911520608.625000 pos:113176 size:852 flags:1
 ret: 0 st:-1 ts:0.624171 flags:1
@@ -3631,7 +3631,7 @@ ret: 0 st: 0 dts:0.043533 pts:-102481911520608.625000 pos:29328 size:21852 flags
 ret: 0 st: 0 ts:2.412500 flags:1
 ret: 0 st: 0 dts:2.408733 pts:-102481911520608.625000 pos:29328 size:9604 flags:1
 ret: 0 st: 1 ts:1.306667 flags:0
-ret: 0 st: 0 dts:1.317933 pts:-102481911520608.625000 pos:-1 size:14617 flags:0
+ret: 0 st: 0 dts:0.740000 pts:0.780000 pos:48504 size:14617 flags:0
 ret: 0 st: 1 ts:0.200844 flags:1
 ret: 0 st: 0 dts:0.200133 pts:-102481911520608.625000 pos:65800 size:18588 flags:1
 ret: 0 st:-1 ts:-0.904994 flags:0