[LCtalk] LanBox UDP disclosed

[Fokko van Duin]

Hello all,

Now that more people have discovered the unique possibilities with 
LanBox UP, it's maybe useful to disclose it's working a bit more in 
depth.

Transferring DMX data using the LanBox UDP protocol, has several 
options of which most people are not aware, but are very handy to 
know if you want to solve more complex setups.

First of all the sender has the option to send "announce" or "write" 
UDP packets. The MAX/Jitter video2DMX example, and the Isadora LanBox 
RGB actor, both have this option.

What is the difference between announce and write?

With announce (or publish) you send the packets to one or multiple 
(broadcast) IP destination(s), but without knowing whether the 
destination(s) will receive it. This is very effective for 
broadcasting (like TV), as any box can choose to pickup whatever the 
box want to receive (or not). This mode is mainly used to transfer 
multiple DMX universes to different LanBoxes, where each box grabs a 
universe from it.

With the "write" option, the destination IP(s) have no choice; they 
will receive those packets. This option is the default for the 
video2DMX demos for MAX (parm2 = 202) and Isadora, as it will always 
work, without any settings to do in the LanBox.


But where is the UDP DMX data going to in the LanBox?
That depends on the mode (announce or write), but also what the 
buffer ID is in the data packets which where sent. Default the ID is 
set to 254, which is the mixer. Again this is the default values as 
when a box is erased, there are no active channels so the mixer data 
will always be seen in LCedit and on your fixtures. As soon as you 
want to use the box also for other things like manual control, 
running cues, using DMX input, etc this UDP usage conflicts.

How can we get UDP data into a layer, so we can use HTP or transparent mode?
Simple by changing the buffer ID to a layer number (as with e.g. DMX 
input). So in 'write" mode with buffer ID = 1, all the UDP data is 
written into layer A, no settings needed?

No, as default there are no channels in a layer active, so there is 
nothing to write to (the same is true for DMX input). You -must- 
first activate the used channels, by e.g. setting them by hand to any 
value. Better is to make a cue with hold for ever, which has all used 
channels set to 0, and run that cue forever in the layer you want to 
write to, with UDP or DMX in. If you do a save LanBox data then, it 
will be correctly restored after power up.

Are you still with me?

Setting the buffer ID is correct for the "write" mode, but if you use 
the  announce/publish mode this won't work!  In the announce/publish 
mode you -must- use buffer ID 254, else the LanBox will ignore it. 
However.. in order to receive those packets, you must setup UDP 
receive for the LanBox in the Global settings. Besides the selected 
range, you can also set any layer (or mixer) as the ultimate 
destination. So also with broadcasted UDP data, you have control 
where it's going to.


Now if you combine all of above with Copy, HTP, LTP, transparent, and 
add mixer mode, you can image that you can create a complex mix of 
video (via UDP), cues, chases, manual sliders (via DMX input). And 
even then the box can broadcast that result to distribute it to other 
universes.

I am going on vacation, knowing for sure that you need at least a few 
weeks to figure out what this email was going about :-) Still, I will 
try to answer your questions during my vacation, if I have some 
internet access.


--
Fokko van Duin,
CDS advanced technology bv,
http://www.lanbox.com/