Error Detection and Handling
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 and places them in an EDH 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 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.
The SD-SDI EDH protocol is defined by SMPTE RP 165-1994 and the equivalent ITU standard ITU-R BT.1304