Error Detection and Handling
Encyclopedia
In television
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
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
video, as the HD serial digital interface includes a mandatory embedded CRC for each line.
The SD-SDI EDH protocol is defined by SMPTE RP 165-1994 and the equivalent ITU
standard ITU-R BT.1304
.
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
technology, Error Detection and Handling (EDH) protocol is an optional but commonly used addition to the Standard Definition-Serial Digital Interface
Serial Digital Interface
Serial digital interface is a family of video interfaces standardized by SMPTE. For example, ITU-R BT.656 and SMPTE 259M define digital video interfaces used for broadcast-grade video...
(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
CRC
- Organizations :* California Rehabilitation Center, a state prison in the USA* Cambridge Regional College, a further education college* Cambridge Regional College F.C., a semi-professional football club in England* Canada Research Chair* Capital Research Center...
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
Ancillary data , in the context of television systems, refers to a means which by non-video information may be embedded within the serial digital interface...
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 television
High-definition television is video that has resolution substantially higher than that of traditional television systems . HDTV has one or two million pixels per frame, roughly five times that of SD...
video, as the HD serial digital interface includes a mandatory embedded CRC for each line.
The SD-SDI EDH protocol is defined by SMPTE RP 165-1994 and the equivalent ITU
Itu
Itu is an old and historic municipality in the state of São Paulo in Brazil. The population in 2009 was 157,384 and the area is 641.68 km². The elevation is 583 m. This place name comes from the Tupi language, meaning big waterfall. Itu is linked with the highway numbered the SP-75 and are flowed...
standard ITU-R BT.1304
External links
- Error detection and handling in digital television
- An Error Measurement Method for Television
- Society of Motion Picture and Television Engineers: Recommend Practice 165-1994: Error Detection and Handling. Available for purchase at the SMPTE website
.