NOPs in pre-command section

[Ghitulescu]

From time to time I see several NOPs in a row before any other pre-command for a PGC.

While officially NOP doesn't do anything, I assume it does however something in this case, most probably a temporisation (a delay), as every command needs CPU time.

Why do they do this?

[mp3dom]

Because often you made a "general" project used for multi-purpose and then adjust accordingly. You made an authoring project for, let's say, movies with 4 languages but when you need to author a dvd with 3 languages, the logic behind need to be adjusted. For example the "GOTO <line>" command doesn't change if you delete some line (I'm referring to Scenarist) with the consequence that if you delete a line, you will point to another target. In that case it's better to "NOP"s the commands that you just don't need, to avoid shifts and mess up the programming. This is just an example (it could be applied to Cell commands for loops and other stuff).

[rik1138]

Abstraction layer authoring systems do this a lot too (like Spruce or DVD Studio). Much for the same reason, there's always 10 lines for this, 10 lines for that, and if all 10 aren't needed, they just pad them with NOPs. I don't think it causes any noticeable delay in playback though.