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Subject: Re: [LCtalk] Feature request...?
From: Matthijs van Duin
Date: Sun, 11 Jan 2004 01:59:28 +0100

On Sun, Jan 11, 2004 at 01:20:44AM +0100, Fokko van Duin wrote:
At 11:27 -0500 10-01-2004, Eric Cornwell wrote:
Are you planning to support Art-Net? Or ACN?

We have looked to three protocols, including Art-Net and ACN, but for what we want I understood that those protocols are not really suited. The problem with those protocols seems to be that they assume only DMX (fixture) distribution, while we also need a protocol to have full control of a box.

Actually, the exact reasons are slightly different, though the basic idea is the correct. ACN and Art-Net don't really fit our needs because they are for controller-slave communication, while we need host-controller and controller-controller communication.

ACN is meant as a replacement for DMX, and is very fixture-oriented. It is also pretty ugly here and there (XML for fixture descriptors.. blegh)

Art-Net is basically just a pure DMX-512 over Ethernet transport, and also puts very awkward restrictions on the IP layer. It doesn't support more than 512 channels, which makes sense when sending DMX-512 to a dumb endpoint.

In our case however the data ends up in a layer and goes through the patcher and post-processing again. It can be quite useful to broadcast, for example, 800 channels to 3 devices, and have them pick up to 512 channels to be sent to DMX out.

Also, for controller->host, we need to indicate which layer the data comes from (a concept unknown to other protocols of course) and deal with things like disabled channels.

Finally, by making a protocol tuned to the task we need it to perform, there is less overhead and complexity. In particular, we want to minimize the burden on the LanBox, as it's still only a small device. (ACN in constast appears to assume a controller with plenty of memory and computing power - witness the use of XML)

--
Matthijs van Duin  --  May the Forth be with you!

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