Video and FC-AV Terms

Typical video frame definitions

This page defines common video terms and specific nomenclature associated with FC-AV. The chart above and text on this page define common video terms used throughout this website.

FC-AV: The Fibre Channel–Audio Video standard. Its official designation of the standard is ANSI INCITS 356-2002. The standard defines the FC-AV container system, which provides a framework for mapping various digital Audio/Video formats.

Video Frame: Refers to an entire "pixel space," for example an XGA image at 1024 x 768 pixels. A video frame may be larger than an image contained therein. The image within a video frame is the Active Image Area.

FC-AV Frame: For transmission, one video frame is broken down into multiple FC-AV frames because an FC-AV frame is limited to 2112 bytes. For example, an XGA image has 3 bytes/pixel and 1024 pixels per line, a total of 3072 bytes. Thus it requires two frames per line, each containing 1536 bytes. An FC frame may contain several rows of video data or less than a single row, depending on the number of pixels in a line and bytes per pixel.

FC-AV Container: An FC-AV term for all the FC Frames taken together, which includes the container header, and various objects representing ancillary data, audio, and video. One container holds a complete Video Frame. The FC-AV Container Structure diagram in the FC-AV Overview shows that within an FC sequence of FC frames, there is a "payload." All of the information in the payload taken together forms the container. By grouping video, audio, and ancillary data into relatively large data sets to be transported as a unit, the container is an optimal transmission system.

Container Objects: Four types of Container Objects are defined within the Simple Header Mode of SPDV profile. Object 0 carries ancillary data; Object 1 carries audio data (but this isn't used in the SPDV profile); Object 2 carries video data; and Object 3 also carries video data, but is only used for interlaced video.

Vertical Sync: Indicates start of frame (start of image container).

Horizontal Sync: Indicates the start of the row timing within the video frame.

Data Enable: Indicates the beginning of active image pixel information.

Horizontal Blanking: This is adopted from an analog CRT perspective. After scanning a horizontal row, from left to right, the electron beam needed time to move from right back to left to begin to scan the next line. The time needed to move the electron beam was the horizontal blanking. In the digital world, the horizontal blanking is the time needed after transmitting an FC Frame (which contains some video data) to transmit that video data to a display. The horizontal blanking is usually filled with IDLE characters.

Vertical Blanking: Like the Horizontal Blanking, this term comes from the analog TV world. The time required to reposition the electron beam from the lower right hand corner, to the upper left hand corner is the vertical blanking. In the digital world, the vertical blanking is the time between video frames. For example, if transmitting at a rate of 30Hz, a new video frame will be sent every 1/30 of a second. If the entire time needed to transmit the frame is 1/60 of a second, then there is 1/60 of a second left over before beginning the transmission of the next video frame, this leftover time is the vertical blanking inserted between each Video Frame. The vertical blanking is accomplished by inserting IDLE characters.

Active Image Area: The image visible on a display, with all special characters are stripped off and vertical and horizontal blanking areas removed.

Horizontal Scan Direction: Adopted from CRT technology, a line is draw from left to right.

Vertical Scan Direction: Adopted from CRT technology, lines are drawn from top to bottom.

Payload: The FC Frame Payload carries all the components of the container (header, ancillary data, and object data). Technically, the Payload is the FC Frame minus the Frame Header, the CRC, and start-of-frame (SOF) and end-of-frame (EOF) delimiters.

Field: For analog TV, a video frame is broken into two fields, a odd field (all the odd lines of a video frame) and an even field (all the even lines)

Interlace: The method by which analog TVs display a video frame, first refreshing the odd field, followed by the even field.

CRC: Cyclic Redundancy Code. The term CRC seems to be reserved for algorithms that are based on the "polynomial" division. The essential mathematical operation in the calculation of a CRC is binary division, and the remainder from the division determines the CRC. CRCs cannot, however, be safely relied upon to verify data integrity. CRC types are often identified by the polynomial, which is the number used as the divisor.

8b/10b Encoding: The IBM patented encoding method used for encoding 8-bit data bytes to 10-bit transmission characters. Data bytes are converted to transmission characters to improve the physical signal such that the following benefits are achieved: bit synchronization is more easily achieved; design of receivers and transmitters is simplified; error detection is improved; and control characters—i.e., the special character—can be distinguished from data characters. This encoding is used by Fibre Channel, Gigabit Ethernet, 10 Gigabit Ethernet, and ATM transmission interfaces.

Simple Parametric Digital Video: SPDV. A profile that defines a container header that has one fixed length header with four objects. SPDV defines a mapping based on the container system defined in Clause 5 of ANSI INCITS 356-2002. The target of this profile is real-time digital video for avionics systems. SPVD uses a Simple Header Mode of operation, which means the container header is exactly 22 long words (88 bytes) in length.

Frame Header Control Protocol: FHCP. This is a low-overhead way to send FC-AV containers, which lends itself to low-latency, efficient data transmission. FHCP is defined in Clause 7 of ANSI INCITS 356-2002.

Special Characters: When using 8b/10b encoding, there are two types of characters: data characters and special characters. When a character is converted from eight bits to ten bits, the serializer must be told if a byte is data or a special character (by asserting a given pin on the serializer). Common special characters are: K28.0, K28.1, K28.2, K28.3, K28.4, K28.5, K28.6, K28.7, K23.7, K27.7, K29.7, and K30.7. These characters can be used to indicate start of frame, end of frame, start of line, end of line, IDLE, or other needed control characters.

Fibre Channel Levels: Fibre channel has multiple layers of implementation, beginning with Level 0, the physical level progressing to Level 4.  FC-AV relies on portions of Levels 0–2, and the Frame Header Control Protocol from Level 4.

Basic Fibre Channel Levels

Level 0 (FC-0)

Level 1 (FC-1)

Level 2 (FC-2)

FC-0 physical interface
Signal characteristics
Bit-error rate reporting
Bit-error rate measurement

FC-1 functions
8b/10b encoding
Ordered sets
Link-level protocols

FC-2 scope
Exchange, sequence, and frame
Session management
The exchange
The sequence
FC-2 service interface
Information unit

FC-AV builds on the basic FC concepts of Level 0–2 and adds containers on top of Level 2. These containers have a container header as defined by the SPDV Profile. FC-AV also adds Frame Header Control Protocol in Level 4 as a method of transporting containers.