Current industry trends
In the absence of a lighting industry standard Ethernet protocol, many
lighting control
and dimmer manufacturers have developed proprietary Ethernet protocol based on TCP/IP.
End equipment manufactures have not yet adapted their equipment for Ethernet. This branch of the lighting industry is more conservative in adopting new technologies and there is a lot of equipment out there (end equipment sales are estimated at 600 million USD a year). Since this end equipment is used for years, the control systems must continue supporting it.
A communal effort spearheaded by an ESTA (Entertainment Services and Technology Association) task force has been developing an Ethernet protocol that will be adopted as the industry standard. Even though this process involves a lot of politics, we all hope that outcome is as successful as the industry adoption of DMX512. The beginning of next year is the target date for publishing the Ethernet protocol specification for use in the entertainment lighting industry.
The bottom line
Standardization is always beneficial to industry and lining up with the rest of the communications industry can only expand the use of this technology in the entertainment field niche. Adopting an Ethernet protocol standard will allow us:
• Well-defined networks using inexpensive and existing equipment
• Effortlessly integrating new developments, such as Wireless Ethernet
• Using Ethernet for transmitting MIDI, SMPTE, ACN, video, and DMX
• Taking advantage of
broad
band technology
Although this section discusses communication technology and lighting in the modern theater, it applies to all venues - television studios, rock concert, discotheques, museums, large commercial spaces, weddings, and exhibitions.
Lighting systems include:
Lighting fixtures - automated and conventional
Control systems
Effects
Dimmers
Synchronization systems for managing sound to light systems
PCs for monitoring and offline programming
The automated fixture revolution
The development of the automated lighting fixtures in the early 1980's caused a revolution in entertainment lighting design. The fixtures were mechanically, electrically, and optically complex. Today these fixtures can have up to forty variables or parameters. Some examples of their functionality include:
Controlling the
beam
movement in the performance space and hall
Using
color mixing
or color subtraction for quality color production
Control
Automated lighting fixtures require a constant flow of information to control tens of parameters. When using a large number of these fixtures, the operator may find herself controlling thousands of variables.
How does an operator control all these variables? What kind of
interface
is needed to set values that, for each parameter, in each fixture and at each point in time, determine a certain behavior?
Only sophisticated control systems can allow us humans to control such a large number of parameters. To illustrate this point, I would have you consider how many parameters we control when driving a car (a most tricky business). The answer is two - speed and direction. So controlling intelligent fixtures in the theater is like driving hundreds of cars going in different directions at different speeds. See what I mean?
Computerized (digital) control boards, such as Compulite's Vector consoles, allow the operator to control all those thousands of parameters just as easily as you drive your car.
Principal uses of communication technology in the theater
In modern theater installations, we use network communication to supply:
Control for hundreds of fixtures that require refresh and updates at frequencies ranging from 40 Hz to 2.5MbPs for large installations.
Status reports that may include dimmer temperature,
lamp
status, over current, and breaker status. Compulite CMX was one of the first protocols to support this bi-directional communication.
Cabled and wireless remote control.
Emergency backup systems.
Synchronization between lighting systems and other media systems.
Servers used for network management, archiving, and monitoring.
Communication protocols
To fully understand the direction of networking in today's theater we should look at the development of communication in the lighting industry. The basic requirement has always been the ability to send a value from the control system to the end equipment.
The analog generation The first communication system was simple analog, transmitting information from the control
console
to the dimmers, over cables having 32 DC lines with current that varied from 0V to 10V. The dimmers, regulating the incoming voltage, sent 220V to the light fixtures.
The next
stage
was AMX192 (Analog Multiplexing), which was adopted as the industry standard by the USITT (US Institute of Theater Technology) in 1975. This protocol transmitted 192 values over four lines with current varying from 0V to 5V at the frequency of 20hz. This was a great improvement over simple analog communication.
One of the major problems with AMX192 was its sensitivity to noise. The introduction of D54 by the Strand Company largely solved this problem. D54 transmitted 384 values.
The digital generation DMX512 (Digital Multiplexing) protocol was developed by the USITT in 1986. DMX512 is a serial protocol based on RS485. It uses three lines that transmit 512 values at the frequency of 250KBPs and an update rate of 40Hz.
Some equipment manufacturers developed proprietary protocols. These were advanced protocols, but none of them succeeded in becoming accepted as standard. That honor belongs to DMX512, which is still the international industry standard protocol for lighting equipment.
Synchronization protocols
With the development of entertainment technology, the need for synchronization between lighting and music or lighting and video became apparent.
MIDI - A common synchronization protocol is
MIDI
(Musical
Instrument
Digital Interface) developed in the 1980's. By today's standards,
MIDI
is an antiquated serial protocol that is slow and transmits only very simple commands.
MSC - The limitations of
MIDI
led to the development of MSC (MIDI
Show
Control), which allows transmitting more complex commands, but suffers from the same weakness as MIDI.
MTC - A sub-protocol within MIDI, MTC (MIDI Time Code) is used to keep two devices that control a timed performance (for example, a sequencer and a video deck) in sync. MTC is essentially SMPTE adapted for
transmission
over MIDI.
SMPTE - This protocol is based on absolute time code values that are usually generated by audio video tapes. Many
lighting control
consoles can be programmed to execute commands triggered by this protocol. This system is usually employed in sound-and-light shows that do not require human intervention. Examples of this can be seen in museums and theme parks.
Ethernet
Ethernet was developed in 1976 by the Xerox Corporation to transfer data over LANs (Local Area Networks). There was no need for Ethernet in theater applications until the middle of the 1990's when more and more lighting designs began to feature large numbers of multi-parameter automated fixtures. This new reality required a method of transmitting massive amounts of information. Lighting crews found the need for increasingly more DMX lines that ran all over the theater. When the DMX512 standard was specified some 20 years ago by the USITT, the need for this amount of control channels had not been foreseen. So at last Ethernet entered the theater. Today we see many uses of Ethernet in entertainment technology: MIDI- over -Ethernet, SMPTE- over- Ethernet, and, of course, DMX- over -Ethernet.
ArtNet, developed by Artistic Licence, is a protocol for transmitting DMX data over IP based networks using UDP. Two examples of the advantages in moving to an IP based network are: a typical 10Mbps Ethernet connection carries 40 times as much data as a single DMX serial and hardware for IP based networks is more available and less expensive than that for the niche lighting market.
Compulite Systems DMX-over-Ethernet implementation
In 1996, Compulite Systems began developing Ethernet support for their lighting systems. This development was triggered by issues that arose during a project in Amsterdam, Holland. Compulite became a pioneer in DMX- over -Ethernet development, just as the company had pioneered the use of computers for
lighting control
two decades earlier.
Virtual Connectors (VCs) formed the basis of Compulite's DMX - over- Ethernet concept. This concept freed us from the limitations of physical DMX connectors by transmitting DMX signals as packets to different components on the LAN. Components are configured to "listen" to specific VCs. Each component can receive VCs, translate the Ethernet
transmission
to DMX512, and send the DMX512 signal on to the end equipment. Each component can also produce VCs, transmitting them via Ethernet protocol across the network via E-Port hubs.
How does this Virtual Connectors concept work? Using TCP/IP protocol, standard for all Ethernet LANs, each component on the network is assigned unique identifier (IP). A VC table is then set up, defining the VCs that the component transmits or receives. Sometimes the same VC or DMX signal is transmitted from more than one component. In this case, the component (such as dimmers or hubs) receiving these transmissions merges the data, translating it into DMX512 that is then sent to the end equipment.
A typical installation
Current industry trends
In the absence of a lighting industry standard Ethernet protocol, many
lighting control
and dimmer manufacturers have developed proprietary Ethernet protocol based on TCP/IP.
End equipment manufactures have not yet adapted their equipment for Ethernet. This branch of the lighting industry is more conservative in adopting new technologies and there is a lot of equipment out there (end equipment sales are estimated at 600 million USD a year). Since this end equipment is used for years, the control systems must continue supporting it.
A communal effort spearheaded by an ESTA (Entertainment Services and Technology Association) task force has been developing an Ethernet protocol that will be adopted as the industry standard. Even though this process involves a lot of politics, we all hope that outcome is as successful as the industry adoption of DMX512. The beginning of next year is the target date for publishing the Ethernet protocol specification for use in the entertainment lighting industry.
The bottom line Standardization is always beneficial to industry and lining up with the rest of the communications industry can only expand the use of this technology in the entertainment field niche. Adopting an Ethernet protocol standard will allow us:
Well-defined networks using inexpensive and existing equipment
Effortlessly integrating new developments, such as Wireless Ethernet
Using Ethernet for transmitting MIDI, SMPTE, ACN, video, and DMX
