television Television, sometimes shortened to TV, is a telecommunication medium for transmitting moving images and sound. The term can refer to a television set, or the medium of television transmission. Television is a mass medium for advertisin ...

technology, Error Detection and Handling (EDH) protocol is an optional but commonly used addition to the Standard Definition- Serial Digital Interface (SDI) standard. This protocol allows an SD-SDI receiver to verify that each field of video is received correctly. The SD-SDI transmitter calculates two CRC values for each video field—one corresponding to the active picture, and corresponding to the entire field (excluding the switching lines)--and places them in an EDH

ancillary data Ancillary data is data that has been added to given data and uses the same form of transport. Common examples are cover art images for media files or streams, or digital data added to radio or television broadcasts. Television Ancillary data (commo ...

packet. The EDH packet is inserted at a specific location in each field of video. The SD-SDI receiver also generates the same two CRC values for each field and compares them against the CRC values in the received EDH packet to determine if each field of video is received without errors. The EDH packet also contains bits to signal that a prior link in a broadcast or transmission chain contained an error; equipment which receives a video signal with an incorrect CRC, and retransmits the signal, is expected to re-insert the correct CRC (which may be different if the equipment alters the video signal in any way) and set the flag indicating a prior error. This feature makes it easier to determine which link, in a multi-link chain, was the source of the error. The EDH protocol does not provide for error correction, only error detection. Also, there is no mechanism in SD-SDI to allow a field containing errors to be retransmitted. EDH is used primarily to assist in identifying faulty equipment in a video chain so that it can be quickly replaced or repaired. EDH is not used with

high definition High definition or HD may refer to: Visual technologies *HD DVD, discontinued optical disc format *HD Photo, former name for the JPEG XR image file format *HDV, format for recording high-definition video onto magnetic tape * HiDef, 24 frames-pe ...

video, as the HD serial digital interface includes a mandatory embedded CRC for each line. The SD-SDI EDH protocol is defined by

SMPTE The Society of Motion Picture and Television Engineers (SMPTE) (, rarely ), founded in 1916 as the Society of Motion Picture Engineers or SMPE, is a global professional association of engineers, technologists, and executives working in the m ...

RP 165-1994 and the equivalent

ITU The International Telecommunication Union is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established on 17 May 1865 as the International Telegraph Unio ...

standard ITU-R BT.1304

External links

Error detection and handling in digital televisionAn Error Measurement Method for Television
*Society of Motion Picture and Television Engineers: ''Recommend Practice 165-1994: Error Detection and Handling''. Available for purchase at th
SMPTE website
. Serial digital interface Digital television ITU-R recommendations

See also

External links