ArtTimeCode allows time code to be transported over the network. The data format is compatible with both longitudinal time code and MIDI time code. The four key types of Film, EBU, Drop Frame and SMPTE are also encoded.
Use of the packet is application specific but in general a single controller will broadcast the packet to the network.
The ArtTimeCode packet can be broadcast or unicast to the network. The decision on which to use is very much application specific. The most common implementation involves a single controller broadcasting to all other devices.
In some circumstances a controller may need the networks devices to be synchronised but with offset times. In this instance, the controller will unicast ArtTimeCode to the network devices.
The ID field is 8 bytes in length and contains the null terminated string of ASCII characters:
A r t – N e t
The purpose of the field is to identify the packet as an Art-Net protocol packet. All Art-Net packets start with this field. Receivers must check this field is correct and discard the packet if it is not.
The OpCode field is a 16-bit word transmitted low byte first. The OpCode identifies the packet type. In the ArtTimeCode packet this field is set to ‘OpTimeCode’.
The ProtVer field is a 16-bit word transmitted high byte first. It identifies the version of the Art-Net protocol. The protocol version is not related to Art-Net 1, II, 3 or 4. Only one protocol version has ever existed in production equipment which is 1410. Receivers should use the following good packet test:
ProtVer >= 14
The ProtVer may be increased in a future releases to identify significant functionality changes.
These fields are used to pad the length of this packet to match the ArtPoll header. They are transmitted as zero and never tested by receivers.
The Frames field is an 8-bit number that defines the number of frames encoded in the time. The value ranges from 010 to 2910, although not all values are legal for all types of time code. See table below.
The Seconds field is an 8-bit number that defines the number of seconds encoded in the time. The value ranges from 010 to 5910.
The Minutes field is an 8-bit number that defines the number of minutes encoded in the time. The value ranges from 010 to 5910.
The Hours field is an 8-bit number that defines the number of hours encoded in the time. The value ranges from 010 to 2310.
The Type field is an 8-bit number that defines the time base of the encoded time. The following table describes the options: