[PD] pdp usage questions

[james tittle]

I'm having alot of fun playing with pdp/pidip in Gem now that I've  
gotten everything stable on my system, but I'm still coming up with  
lots of questions where things don't work the way they seem...

...when using [pdp_trigger], is this the same as just drawing two  
connections from the same object?  Fr'instance, many examples have  
the two connections from the [pdp_gain] to [pdp_mul]'s inlets:   
what's this supposed to do?

...similarly, some objects accept a [chanmask $1< message, but it's  
not always clear which ones:  I assumed that chanmask 1/2/3  
corresponded to Y/U/V, but then I came across an example with  
chanmask 4, so what do these actually represent?

...is there an object that blends the Y from one packet with the CrCb  
from another?

...the bitwize (sic) operators are weird, too:  do they accept  
channel masks?  does [pdp_sign] just change the sign, and does  
[pdp_abs] just give absolutes of the channel values?

...finally (for now), is there any documentation for the matrix  
manipulators?  I haven't been able to get them to do anything, and  
[pdp_pointcloud] seems unfinished...

thanx for any insights,
james