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Art-Net II Protocol Release V1.4 Document Revision 1.4ao 26/8/2010

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Data Merging:
The Art-Net protocol allows multiple nodes or servers to transmit ArtDmx data to the same universe.
A node can detect this situation by comparing the IP addresses of received ArtDmx packets. If
ArtDmx packets addressed to the same Universe are received from different IP addresses, a
potential conflict exists.
The Node can legitimately handle this situation using one of two methods:
• Consider this to be an error condition and await user intervention.
• Automatically merge the data.
Nodes should document the approach that is implemented in the product user guide. The Merge
option is preferred as it provides a higher level of functionality.
Merge is implemented in either LTP or HTP mode as specified by the ArtAddress packet.
Merge mode is implemented as follows:
1. If ArtDmx is received from differing IP addresses, the data is HTP merged to the DMX
output. In this situation, ArtPollReply-GoodOutput-Bit3 is set. If Art-Poll-TalkToMe Bit 1 is
set, an ArtPollReply should be transmitted when merging commences.
2. Exit from Merge mode is handled as follows:
• If ArtAddress AcCancelMerge is received, the Next ArtDmx message received
ends Merge mode. The Node then discards any ArtDmx packets received from an
IP address that does not match the IP address of the ArtDmx packet that
terminated Merge mode.
• If either (but not both) sources of ArtDmx stop, the failed source is held in the
merge buffer for 10 seconds. If, during the 10 second timeout, the failed source
returns, Merge mode continues. If the failed source does not recover, at the end
of the timeout period, the Node exits Merge mode.
• If both sources of ArtDmx fail, the output holds the last merge result.

Merging is limited to two sources, any additional sources will be ignored by the Node.
The Merge implementation allows for the following two key modes of operation.
• Combined Control: Two Servers (Consoles) can operate on a network and merge data to
multiple Nodes.
• Backup: One Server (Console) can monitor the network for a failure of the primary Server.
If a failure occurs, it can use the ArtAddress AcCancelMerge command to take instant
control of the network.

When a node provides multiple DMX512 inputs, it is the responsibility of the Node to handle merging
of data. This is because the Node will have only one IP address. If this were not handled at the
Node, ArtDmx packets with identical IP addresses and identical universe numbers, but conflicting
level data would be transmitted to the network.