Only sliders have an identifying value which is constant, meaning it will always be '133769' (funny, I know) - so if you see this, you know that below it holds a slider note.
Note type values (W, A, D or S) are also constant, I don't know this off by heart but the note type for W is literally just the ASCII code for the W character, and so on for the others.
Unfortunately I don't remember completely how info.songdata is structured, but I think with a bit of tinkering it could be understood pretty fast. The song name and description is obvious and apart from them - if I'm not mistaken - the only other values are the difficulty, speed and offset. Their order I am unsure of.