Some versions of Isadora’s ArtNet Send and ArtNet Receive actors (ArtNet Send <= 1.0.5 and ArtNet Receive <= 1.0.6) have a known limitation when more than four Art-Net universe values are used at the same time.

Testing with ArtNet Send 1.0.5 shows that up to four universe addresses can be active within each subnet at the same time.

The individual universe values are not restricted to 0–3. Any of the 16 available AN Universe values within a subnet may be used. The limitation is on how many different universe addresses are active in that subnet at once.

If you are new to Art-Net addressing, see:

[Using Art-Net Addressing in Isadora]

That article explains how Isadora’s universe input relates to the AN subnet and AN universe values shown on the actor.

Important

This is a limitation of the affected Isadora ArtNet actor, not a limitation of Art-Net itself.

TroikaTronix plans to address this behavior in a future actor update. This article will be updated when corrected versions become available.

Understanding the Limitation

Each ArtNet Send actor has a universe input.

Isadora converts this number into:

• AN subnet
• AN universe

For example:

Each subnet contains 16 possible AN Universe values, numbered 0–15.

With the affected ArtNet Send actor, testing shows that only four of those universe addresses can be active within the same subnet at one time.

The Universe Values Themselves Are Not Restricted

It is important to distinguish between:

• which AN Universe numbers are allowed, and
• how many can be active at once.

For example, these four addresses can all be valid within subnet 0:

0, 1, 2, 3

But there is nothing special about those particular numbers.

A different set of four may also be used, such as:

8, 9, 10, 15

or:

2, 5, 10, 14

The important rule is:

Do not use more than four active Art-Net universe addresses within the same AN subnet.

What Happens When a Fifth Universe Is Added?

Suppose five ArtNet Send actors are configured with:

0, 1, 2, 3, 4

All five addresses belong to:

AN subnet 0

The first four actors can initialize successfully, but the fifth may report:

ready = off

The problem is not that AN Universe 4 is invalid.

If 4 is used by itself, or as one of no more than four addresses in that subnet, it can be used normally.

The problem occurs because five addresses are being requested within the same subnet.

Using Additional Subnets

To use more than four Art-Net universe addresses, distribute them across additional AN subnets.

For example:

This gives four addresses in subnet 0 and four more in subnet 1.

You can continue the same pattern into additional subnets:

0–3
16–19
32–35
48–51
64–67

and so on.

This pattern is easy to remember, but it is only one possible arrangement.

For example, the following would also stay within the four-address-per-subnet limit:

4, 7, 10, 15

then:

20, 23, 26, 31

The important point is the number of active addresses in each subnet, not the specific AN Universe numbers chosen.

A Simple Eight-Universe Setup

A straightforward way to configure eight Art-Net universes is:

This keeps each subnet within the four-address limit.

Remember to Configure the Receiving Equipment

Changing the Isadora universe input changes the actual Art-Net address being transmitted.

For example:

universe = 4

means:

AN subnet = 0
AN universe = 4

while:

universe = 16

means:

AN subnet = 1
AN universe = 0

These are different Art-Net addresses.

If you move an Isadora universe into another subnet to stay within the four-address limit, the receiving Art-Net hardware or software must also be configured for the new address.

Checking the ready Output

The ArtNet Send actor provides a:

ready

output.

When:

ready = on

the actor has successfully initialized and is ready to transmit Art-Net.

If:

ready = off

check how many ArtNet Send addresses are already active in the same AN subnet.

If more than four are being used, move one or more addresses to another subnet.

Example Troubleshooting

Suppose you have:

8, 9, 10, 11, 12

All five values belong to:

AN subnet 0

This exceeds the four-address-per-subnet limit.

You could instead use:

8, 9, 10, 11, 24

because:

8, 9, 10, 11

belong to subnet 0, while:

24

corresponds to:

AN subnet = 1
AN universe = 8

The receiving equipment for that fifth universe must also be changed to subnet 1, universe 8.

Current Version Status

This behavior has been reproduced with:

ArtNet Send 1.0.5

Testing shows that:

• Any AN Universe value from 0–15 can normally be selected within a subnet.
• Up to four Art-Net universe addresses can be active within that subnet.
• Attempting to create a fifth address within the same subnet may result in ready = off.
• Additional addresses can be created by using another AN subnet.

A future version of the ArtNet actor is expected to improve this behavior.

Once corrected versions are released, this article will be updated to identify:

• the first fixed version,
• which older versions are affected,
• and whether existing Isadora projects require any changes.

Additional Known Issue: AN Subnet 2

During testing of ArtNet Send 1.0.5, an additional issue was observed specifically with:

AN subnet 2

This corresponds to Isadora universe values:

32–47

Unlike the other tested subnets, subnet 2 did not always allow a fourth Art-Net universe address to be created normally.

Testing showed:

• The first three addresses in subnet 2 generally initialized correctly.
• Adding a fourth address could result in ready = off.
• In one test, universe = 37 was able to initialize as the fourth address while several neighboring values could not.
• Universe values that initially failed could sometimes be used successfully by changing the address of an actor that had already initialized.

Recommendation

Do not treat 37 as a special or preferred universe number.

If you encounter unexpected ready = off behavior while using subnet 2, try using another Art-Net subnet instead.

Other tested subnets, including subnets 0, 1, 4, and 5, followed the expected four-address-per-subnet behavior.

TroikaTronix is investigating the subnet 2 behavior separately.

Quick Reference

Maximum observed per subnet

Four active Art-Net universe addresses

Available AN Universe values

Any value from:

0–15

Example valid subnet 0 setup

0, 4, 8, 12

Example that exceeds the limit

0, 1, 2, 3, 4

Add more universes

Use another subnet.

For example:

0, 1, 2, 3

then:

16, 17, 18, 19

Status to check

ready = on

Additional warning

AN subnet 2 (32–47) has shown an additional allocation issue in ArtNet Send 1.0.5. If you encounter inconsistent behavior there, use another subnet until an updated actor is available.