SCR and PTS values reset to zero every 17 secs

[ipanema]

I have several VOB files where the SCR and PTS timestamps reset to zero every 17 seconds or so. I know that SCR and PTS values will eventually wrap round, but that would take many hours to happen. This is happening every 17 seconds approx, and always at a GOP start.

Below is some abbreviated output from DGIndex which illustrates what is happening.

Any idea why they are encoded this way?


DGIndex Timestamps Dump

frame rate = 25.000000
leading B frames = 2
SCR 91545600, [3390ms]
SCR 91589486, [3392ms]
V PTS 330419 [3671ms]
V DTS 319619 [3551ms]
GOP start
Decode picture: temporal reference 2[I]
SCR 91633372, [3393ms]
SCR 91677257, [3395ms]
SCR 91721143, [3397ms]
SCR 91765029, [3398ms]
....
....
....
SCR 465276343, [17232ms]
SCR 465320229, [17234ms]
SCR 465408000, [17237ms]
SCR 0, [0ms] <<<<<<<<< RESET TO ZERO
SCR 43886, [1ms]
V PTS 31713 [352ms]
V DTS 20913 [232ms]
GOP start
Decode picture: temporal reference 2[I]
SCR 87771, [3ms]
SCR 131657, [4ms]
SCR 175543, [6ms]
....
....
....
SCR 466987886, [17295ms]
SCR 467031771, [17297ms]
SCR 467119543, [17300ms]
SCR 0, [0ms] <<<<<<<<< RESET TO ZERO
SCR 43885, [1ms]
V PTS 29701 [330ms]
V DTS 18901 [210ms]
GOP start
Decode picture: temporal reference 2[I]
SCR 87771, [3ms]
SCR 131657, [4ms]
SCR 175542, [6ms]
....
....
....
SCR 479583085, [17762ms]
SCR 479626971, [17763ms]
SCR 479670857, [17765ms]
SCR 0, [0ms] <<<<<<<<< RESET TO ZERO
SCR 43886, [1ms]
V PTS 29052 [322ms]
V DTS 18252 [202ms]
GOP start
Decode picture: temporal reference 2[I]
SCR 87772, [3ms]
SCR 131658, [4ms]
SCR 175543, [6ms]
...
...
...