Apple DVD Studio Pro 4 - Manual (Page 504)

SPRM 5: Current Title Number in Video Title Set (VTS)
In projects created with DVD Studio Pro, the title number within the current Video Title
Set (VTS) number is 1 for all elements, except stories. Each story within a track is assigned
to a higher title number, starting with 2 (the track itself is number 1).
SPRM 6: Current Title PGC Number
In projects created with DVD Studio Pro, the Program Group Chains (PGC) number is 1
for all elements, except stories. Each story within a track is assigned a number, starting
with 2 (the track itself is number 1). This value matches the SPRM 5 value except in the
case where a track, story, or slideshow has not yet been played. In that case, it is set to
0.
SPRM 7: Current Part of Title Number
The Part of Title is the current chapter number of the track being played.
This SPRM is useful if you need to know the last or current chapter played for that track.
There may be reasons to jump to the beginning of the last chapter played from any menu,
not just resume to the last place in the video. An example of this would be a training film
that requires the viewer to resume watching the chapter from the beginning if they do
not watch the chapter in its entirety.
SPRM 8: Current Highlighted Button Number
This SPRM is the last button number of the current or last menu displayed. You can use
this SPRM to track the last button position that the viewer selected. The value is calculated
by multiplying the button number by 1024 (this SPRM uses bits 10 through 15 to count
the buttons).
The table below lists the button number and its value:
SPRM 8 value Button number
1024 1
2048 2
3072 3
4096 4
5120 5
6144 6
7168 7
8192 8
9216 9
10240 10
11264 11
504 Chapter 20 Creating Scripts