History of the ARINC 818 Protocol
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Foundations of ARINC 818
Avionics programs required a new video protocol specifically to break the stranglehold of custom video protocols offered by cockpit display vendors. Each company offered a proprietary format and there were no COTS tools available to test or validate these custom protocols. The formal group that created the standard included participants from most aircraft OEMs and display vendors. They formed the Digital Video Subcommittee of ARINC.
Originally released in January of 2007, ARINC 818 added a standard for high-speed, uncompressed, deterministic, high-bandwidth, low-latency video to the ARINC family. Each of these attributes was carefully chosen. For example, compression adds latency and may result in loss of the level of detail found in avionics video. To compensate for the larger amounts of data to be transferred as a result of not utilizing compression, high bandwidth was included as another cornerstone characteristic of the ARINC 818 protocol.
As technology has advanced through the years, so has ARINC 818. Supplements preemptively included and expanded areas for potential growth, rather than waiting until there was a desperate need for them in the field
ARINC 818 Basics
ARINC 818 achieved an extremely flexible protocol by building on the existing Fiber Channel Audio Video (FC-AV) protocol, which was already being used in aerospace projects. This allowed users to define individual project requirements including resolution, link rates, and pixel packing modes in an Interface Control Document (ICD), and choose to add individual features such as channel-bonding, multiple streams on a single link, additional ancillary data, and choosing a synchronization class. ICDs only need to align with the parameter ranges defined in the standard and must match other devices that communicate directly within a system. By allowing variation in parameters and feature selection on a project-by-project basis, the extent of certification efforts could be minimized to include only necessary elements.
While the ARINC 818 standard uses a simplified implementation of the FC-AV protocol as its base, it does not define a specific physical medium that must be used. With this being said, the protocol is almost always implemented on fiber due to its advantageous size, weight, and bandwidth; however, coaxial cable is another option.
ARINC 818-1: Clarifying the Base Standard
The first supplement, ARINC 818-1, included minor changes to the original standard and was released later the same year, in September 2007. The modification included updated video frame information and clarification to the original release.
General Updates
ADVB Frame format coordination with ANSI
Clarifications
Clarification on ADVB parameters, a timing example, and display timing types
ARINC 818-2: Supporting Complex Systems
In 2013, ARINC 818-2 expanded existing parameters and introduced new features. Systems viable for and/or using ARINC 818 were becoming more complex and beginning to include a wider range of components in addition to cameras, such as sensors, processors, and switches, some of which require the transfer of only data rather than video.
ICD Parameter Updates
A set of higher link rates was added to accommodate the advances in avionics video equipment. Similarly, the allowable refresh rates were expanded.
Faster FC link rates, in Gbps, of: 6.375 (FC 6X), 12.75 (FC 12X), 14.025 (FC 16X), 21.0375 (FC 24X), 28.05 (FC 32X)
Additional link rate of 5.0 Gbps added
Additional codes for 120 Hz and a custom refresh rate
New Features
With the wider range of components being introduced to systems using ARINC 818, new features were added to support the expansion in applications and advancement in technology.
Video compression flag to indicate the video is compressed
Video encryption flag to indicate the contents are encrypted
Video switching guidelines (can’t break video frames)
Support for Field Sequential Color (FSC)
Bi-directional camera interfaces and synchronization
Data only link identification
Expansion of multiple link support
Segmented line – channel bonding
Support for stereo/3D displays
Optical signal performance
Clarification
More guidance for the computation of Prior Image CRC
Notes specifying whether a link rate shall use 8B/10B and 64B/66B encoding were added to each link rate
More information about multiple link support using pixel interleaved – dual link implementation
ARINC 818-3: Reinforced Future Proofing
In 2018, the ARINC standard was updated for its third supplement to support updated and emerging methods of video display, such as higher-resolution 8K displays, VR, and windowless cockpit applications.
ICD Parameter Updates
While 64B/66B encoding and the FC 32X link rate were originally introduced in ARINC 818-2, the additional option of 256B/257B encoding at the FC 32X rate was added in this supplement. The specific, non-FC link rates of 10.0 Gbps and 12.0 Gbps were also added to increase physical layer support.
Addition of non-FC rates
10.0 Gbps using 8B/10B encoding
12.0 Gbps using 64B/66B encoding
Allowance for FC 32X link rate to use either 64B/66B or 256B/257B encoding
Clarification
Definitions for test equipment emulation mode
Latency budget description
Conclusion
ARINC 818 started as a reliable and robust choice for interfacing to cockpit displays, and has continued to evolve to meet the growing demands of modern avionics systems and mission systems as a video backbone.
For those interested in a deeper knowledge of ARINC 818, Great River Technology has created training programs and an extensive repository of learning material at arinc818-academy.com. Sign up for free to access additional content as a member of the site, and a member of our team will reach out to you to approve your application.
