Operators

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We have already shown some examples of operators that can be used with GPRM registers. Most notably you may recognize the obvious

GPRM1 = 15

from previous pages. This is one of the many operators and it is called simply Assign operator. On the previous page you may also have read about Syntax normalization and that DVD-lab VM editor is quite open minded to various syntaxes, however it will always change the command into its native syntax

Operator Name

DVD-lab Syntax Example

Alternative syntax

Meaning

Assign

GPRM1 = 15

GPRM1 = GPRM2

GPRM1 = SPRM1

mov GPRM1, 15

GPRM1 mov 15

MOV(GPRM1, 15)

Assign value or value from register to another register

Swap

GPRM1 <-> GPRM2

swp GPRM1, GPRM2

GPRM1 swp GPRM2

SWP(GPRM1,15)

Swap the two registers

Addition

GPRM1 += 15

GPRM1 += GPRM2

add GPRM1, 15

GPRM1 add 15

ADD(GPRM1,15)

GPRM1 = GPRM1 + 15

Subtraction

GPRM1 -= 15

GPRM1 -= GPRM2

sub GPRM1, 15

GPRM1 sub 15

SUB(GPRM1,15)

GPRM1 = GPRM1 - 15

Multiply

GPRM1 *= 15

GPRM1 *= GPRM2

mul GPRM1, 15

GPRM1 mul 15

MUL(GPRM1,15)

GPRM1 = GPRM1 * 15

Divide

GPRM1 /= 15

GPRM1 /= GPRM2

div GPRM1, 15

GPRM1 div 15

DIV(GPRM1,15)

GPRM1 = GPRM1 / 15

Remainder

GPRM1 %= 15

GPRM1 %= GPRM2

mod GPRM1, 15

GPRM1 mod 15

MOD(GPRM1,15)

Remainder or modulo after division

GPRM1 = GPRM1 % 15

Random

GPRM1 rnd 15

GPRM1 rnd GPRM2

rnd GPRM1, 15

RND(GPRM1,15)

Random value between 0-15

AND

GPRM1 &= 15

GPRM1 &= GPRM2

and GPRM1, 15

GPRM1 and 15

AND(GPRM1,15)

Logical AND

OR

GPRM1 |= 15

GPRM1 |= GPRM2

or GPRM1, 15

GPRM1 or 15

OR(GPRM1,15)

Logical OR

XOR

GPRM1 ^= 15

GPRM1 ^= GPRM2

xor GPRM1, 15

GPRM1 xor 15

XOR(GPRM1,15)

Logical XOR

From the above table it is clear that the left side of an operator can only be a GPRM register. The right side of an operator can be another GPRM register, SPRM register or constant.

If Condition

To check the condition of GPRM registers there is a command if (.....) .....

Example used previously:

if (GPRM1 ==2 ) LinkPGCN 4

But there are more operands than just ==

Operator

DVD-lab Syntax Example

Meaning

==

if (GPRM1 == 15)

if (GPRM1 == GPRM2)

if (GPRM1 == SPRM2)

if GPRM is equal (make sure you type two equal signs == )

!=

if (GPRM1 != 15)

if (GPRM1 != GPRM2)

if (GPRM1 != SPRM2)

if GPRM is not equal

>=

if (GPRM1 >= 15)

if (GPRM1 >= GPRM2)

if (GPRM1 >= SPRM2)

if GPRM is greater or equal

>

if (GPRM1 > 15)

if (GPRM1 > GPRM2)

if (GPRM1 > SPRM2)

if GPRM is greater

<=

if (GPRM1 <= 15)

if (GPRM1 <= GPRM2)

if (GPRM1 <= SPRM2)

if GPRM is less or equal

<

if (GPRM1 < 15)

if (GPRM1 < GPRM2)

if (GPRM1 < SPRM2)

if GPRM is less

&

if (GPRM1 & 15)

if (GPRM1 & GPRM2)

if (GPRM1 & SPRM2)

if logical and is not zero

From the above table it is clear that the left side of an operator can only be a GPRM register. The right side of an operator can be another GPRM register, SPRM register or a constant.

Almost all other commands can be used with comparison (there are some exceptions), however you can not always compare GPRM to a constant value.

For example:

if (GPRM1==2) LinkPGCN 1

is valid, but

if (GPRM1==2) JumpSS VMGM 1

is not valid. You have to use two lines

GPRM2 = 2

if (GPRM1==GPRM2) JumpSS VMGM 1

Generally JumpSS type, CallSS type and Set type (SetHL_BTN for example) can't be used together in comparison with a constant.

Combination Condition commands

Because some places on a DVD allow only one line of commands (most notably for button and cell commands), the DVD specs allow for special combination commands. What this means is, they can have up to 3 commands on one line where one is a condition, the second is an operator and the last is a link. There are also three different ways to put them together. Note how the curly parenthesis differ on the first two lines:

•if (GPRM1 == GPRM2) { GPRM1 = 5 } LinkTopC (button 1)
•if (GPRM1 == GPRM2) { GPRM1 = 5, LinkTopC (button 1) }
•GPRM1 = 5, if (GPRM1 == GPRM2) LinkTopC (button 1)

The first is Condition then {operator} if condition is true and then link regardless the condition

Second is Condition then {operator and link} if condition is true

Third is operator, then condition and link if condition is true.

Unfortunately not all link commands can be used in this combo. Only link types of: LinkNoLink, LinkTopC,....,LinkTopPG, .....LinkTopPGC, .... LinkTailPGC

It is not very probable you would need to use this type of command.

Set combination commands

A few Set commands are allowed in combination with a Link (except in combination with a condition). These are useful for places such as Button in a menu.

SetHL_BTN GPRM1, LinkPGCN 1

Sets the highlighting register to value in GPRM1 and then Link to PGC 1

SetSTN (audio=1 subp=2:on angle=3 ) LinkPGCN 2

Set Audio/Subpicture/Angle Stream and then link to PGC 2. This can be used for example on menu to select subtitles and then immediately link to a different menu where the subtitles text is shown as selected.