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sACN: Artistic Licence products

The sACN (streaming ACN) protocol is supported in Artistic Licence ethernet products. The differences between Art-Net and sACN lead to some minor clashes which this document seeks to clarify.

Universe numbering

In Art-Net, universes are called Port-Address and number from 0 to 32,767. There are 32,768 unique numbers.

In sACN, universes number from 1 to 63,999. There are 64,000 unique numbers. The standard reserves the values of 0 and 64,000 to 65,535 for future expansion.

Clearly there is the potential for confusion over the number ‘0’. If a universe is set to ‘0’ and the sACN protocol is selected, Artistic Licence products will use a universe value of ‘1’ instead.

Merging and arbitration

The sACN protocol uses a concept called Component Identifier (CID) as a method to optionally distinguish unique streams of data, and a concept called Priority as a method to define the priority of a stream.

 

The following table defines how sACN packets A & B are arbitrated or merged when directed to same universe.

CID Priority What happens?
A=B A=B Streams A and B are identical and are output as DMX.
A<>B A=B Streams A and B are from different controllers but have same priority. The streams will be merged using the LTP/HTP settings of the product. A maximum of two streams can be merged. If a third stream appears it will be ignored.
A=B A>B Streams A and B are from the same controller and A has higher priority. B is ignored and A is output. If A stream stops for more than a 5 second time out period, the lower priority stream will take over. If a stream with a higher priority that which is outputting is detected, the higher priority stream immediately takes precedence.
A=B A<B Streams A and B are from the same controller and B has higher priority. A is ignored and B is output. If A stream stops for more than a 5 second time out period, the lower priority stream will take over. If a stream with a higher priority that which is outputting is detected, the higher priority stream immediately takes precedence.
A<>B A>B Streams A and B are from different controllers and A has higher priority. B is ignored and A is output. If A stream stops for more than a 5 second time out period, the lower priority stream will take over. If a stream with a higher priority that which is outputting is detected, the higher priority stream immediately takes precedence.
A<>B A<B Streams A and B are from different controllers and B has higher priority. A is ignored and B is output. If A stream stops for more than a 5 second time out period, the lower priority stream will take over. If a stream with a higher priority that which is outputting is detected, the higher priority stream immediately takes precedence.