Control/Dimming - ACN/RDM

[punktech]

i was just wondering what everyone here thought of these two new acronyms. i'm pretty excited, personally. i think they'll make like a lot easier. no more hanging in horrible positions to address oddly hung DMX devices!

[gafftaper]

It is very exciting but as I sort of ranted about a little too much 6 months ago don't get too excited just yet. It may be quite a while before it becomes a reality. These things take a long time for the industry to adopt and implement. The ability to do this has been there quite a while (Two of those five DMX lines just sitting waiting for someone to use them). Clearly there is a matter of market forces being read to pay for it and control consoles being ready to make use of it. Well we are slowly getting there and everyone wants to brag that their latest gear is ACN/RDM "READY" or "Compatible". However as we learned with P.C.'s being "Vista Ready"... that may not mean much.

So yeah it's cool... but I think we are going to have LED Source4's before RDM is something that is a full reality... so don't hold your breath.

[jfitzpat]

RDM seems like a sensible, incremental improvement that fits reasonably well in existing wiring and infrastructure.

ACN seems like a huge, rather vague, pipedream that seeks to solve a problem that I am not 100% sure even exists (I haven't lost much sleep over, say, multi-controller, multi target infrastructure).

Just my opinion.
-jjf

[CLEFFEL]

The thing I'm looking forward to the most with ACN is that it will consolidate the numerous E-DMX protocols out there into one (ala DMX in the 1980's). We're not looking at DMX being replaced, just the backbone really.

[BenFranske]

Except perhaps for large moving light fixtures which can sometimes use 20 or more DMX channels. That starts to eat away at the available DMX channels on your universe rather quickly. ACN is likely to be a boon to people who have to work in situations with many of these fixtures.

[jmabray]

RDM does not use the other two wires in the 5 pin dmx line. It sends packets at the start of the dmx stream over the same wires that DMX uses.

[TimMiller]

I think something needs to come into play soon. Using 4 DMX universes to control just 8 DL2's is a little rediculous. I think DMX needs to eventually have error correction. It would really help solve glitches every now and then.

[gafftaper]

The frustrating thing is that standard computer networking gear has had all the technology needed to solve all these problems for years. There's no reason you shouldn't be able to plug a dozen DL2's in via ethernet cable, have the network identify them, and then just use them without the constraints of DMX universes.

The technology is all there... and it's not even expensive anymore. It's just a matter of getting the manufacturers to sit down and agree on standards and start building to those standards... which again will take years.

[jfitzpat]

If I didn't make it clear above, the standards are two very different things.

RDM (Remote Device Management) is an attempt to standardize something that High End has already demonstrated. Namely, using the bi-directional capability of RS-485 to remotely obtain information about a DMX and configure it.

There is no new wiring or pairs. The standard outbound pair is used to send a non-valid DMX packet which is recognized as a discovery sequence. The controller then turns the RS-485 line around and listens while devices broadcast.

No new wiring, no significant cost of goods (you need to control the previously strapped T/R lines on your tranceiver and add a resistor bridge for proper termination), and some nice benefits - remote error check, addressing, etc.

Like I said, a nice incremental improvement.

ACN (Architecture for Control Networks) is an attempt to create a master controller of diverse sub control systems - all in the form of a TCP/IP protocol. I think it has three problems facing it.

First and foremost, it is a suprisingly high level standard. Once you start getting to high level, universal show control, there are a *lot* of design decisions, institutionalizing one path out of many makes wide adoption a more uphill battle. I thought it was very telling that RDM, which is a fairly incremental improvement to DMX-512 was initially a pretty tough fit for ACN. To me, that does not bode well for the standards ability to grow and adapt.

Second, when you examine it in a decision tree, the protocol is surprisingly complicated. So much so that most folks still assume that ACN will not widely replace the DMX-512 connector on fixtures, but be a "backbone" between smart nodes, with DMX-512A convertors to get to to actual lights. The worry is that ACN is too complicated to be targetted on simple fixtures.

Third, it is not clear to me what major problems that ACN solves when we have a very simple standard, like ArtNet (which already has provisions for RDM) now. Off the shelf 100BaseT NIC adapters easily support 24 universes at high update rates (above 25 Hz or so, more than 24 universes starts causing packet order reversals on some NIC chipsets, which most simple ArtNet receivers do not handle). Native ArtNet support continues to grow (I use ArtNet now to talk to two Media servers), and the standard is open. Sure, it is pretty lame, but it is simple, and ArtNet<>DMX512 adapters are becoming more and more plentiful and affordable.

I am not saying ArtNet and ACN are the same - they are not. ArtNet looks to address a specific problem - DMX wiring being a costly pain, and does so with simple existing LAN technology. ACN can be used to address the same problem, but comes with the complexity of a master control system. I could be wrong, but in my experience simple standards, even fairly lame ones like MIDI and DMX-512 often 'win'.

-jjf

[SteveB]

Originally Posted by jfitzpat

If I didn't make it clear above, the standards are two very different things.
RDM (Remote Device Management) is an attempt to standardize something that High End has already demonstrated. Namely, using the bi-directional capability of RS-485 to remotely obtain information about a DMX and configure it.
There is no new wiring or pairs. The standard outbound pair is used to send a non-valid DMX packet which is recognized as a discovery sequence. The controller then turns the RS-485 line around and listens while devices broadcast.
No new wiring, no significant cost of goods (you need to control the previously strapped T/R lines on your tranceiver and add a resistor bridge for proper termination), and some nice benefits - remote error check, addressing, etc.
Like I said, a nice incremental improvement.
ACN (Architecture for Control Networks) is an attempt to create a master controller of diverse sub control systems - all in the form of a TCP/IP protocol. I think it has three problems facing it.
First and foremost, it is a suprisingly high level standard. Once you start getting to high level, universal show control, there are a *lot* of design decisions, institutionalizing one path out of many makes wide adoption a more uphill battle. I thought it was very telling that RDM, which is a fairly incremental improvement to DMX-512 was initially a pretty tough fit for ACN. To me, that does not bode well for the standards ability to grow and adapt.
Second, when you examine it in a decision tree, the protocol is surprisingly complicated. So much so that most folks still assume that ACN will not widely replace the DMX-512 connector on fixtures, but be a "backbone" between smart nodes, with DMX-512A convertors to get to to actual lights. The worry is that ACN is too complicated to be targetted on simple fixtures.
Third, it is not clear to me what major problems that ACN solves when we have a very simple standard, like ArtNet (which already has provisions for RDM) now. Off the shelf 100BaseT NIC adapters easily support 24 universes at high update rates (above 25 Hz or so, more than 24 universes starts causing packet order reversals on some NIC chipsets, which most simple ArtNet receivers do not handle). Native ArtNet support continues to grow (I use ArtNet now to talk to two Media servers), and the standard is open. Sure, it is pretty lame, but it is simple, and ArtNet<>DMX512 adapters are becoming more and more plentiful and affordable.
I am not saying ArtNet and ACN are the same - they are not. ArtNet looks to address a specific problem - DMX wiring being a costly pain, and does so with simple existing LAN technology. ACN can be used to address the same problem, but comes with the complexity of a master control system. I could be wrong, but in my experience simple standards, even fairly lame ones like MIDI and DMX-512 often 'win'.
-jjf

This was very informative and well written. I think the issue with ArtNet is that it's a propriatary protocal, where as ACN is not, thus there's no potential *cost* for using ACN, as there might be with companies adopting, and then having to pay for continual usage of the ArtNet protocal. That's the general idea behind ACN, though I suspect you are correct in that, by being an all-things-for-everyone protocal, it's way too complex and doesn't readily solve a simple problem without a lot of effort by a lot of companies, namely how to get all those assorted consoles and appliance to be smarter in their interaction.

Big question is, why hasn't RDM taken off ?. Possibly as everyone is waiting for the next thing - ACN ?, with nobody wanting to commit to something simple, yet useful such as RDM, and then getting hammered on a bid for not being "ACN Ready".

SB