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Introduction to FC-AV

Fibre Channel Audio Video (FC-AV) is a protocol for transporting digital video. It is based on ANSI INCITS 356-2002. As of mid-2013, FC-AV remains active in a some ongoing programs, but in new programs it has been supplanted by newer protocols such as ARINC 818.

Fibre Channel (FC) is used for networked, high-volume storage area networks (SANs). It is a subset of FC, but is not necessarily compatible with commercial off-the-shelf (COTS) FC devices because FC-AV is typically unidirectional.

A key benefit of FC-AV is its low overhead, which allows for real-time transmission of video signals at high frequencies—1.0625 Gbps and beyond using copper or fiber optic cables. On fiber, video can be transported over long distances (limited to 500 meters to 10 kilometers, depending) with no electromagnetic interference.

The FC-AV protocol converts each video frame into a Fibre Channel container. Within the container are segments called FC frames. Note that FC frames do not correspond to video frames. Rather, FC frames are packets within the container. Each is limited to 2112 bytes, which may require a single line of a video frame to be broken into multiple FC frames. In the XGA example below, each of the 1024 RGB pixels in a line requires three bytes (3072 bytes per line), so a video line must be divided between two 2112-byte FC frames.

FC-AV example: Transmission of an XGA video frame in 24-bit RGB.

In avionics, typically, the source of the video frame is a graphics generator or mission processor and the target is a display unit. Transmission involves these steps:

  1. Video packaged into FC frames, with idles added to accommodate timing
  2. Serialization and 8b/10b encoding
  3. Serial transmission
  4. 8b/10b decoding
  5. Reconstruction, including the stripping of idles