(1) In analog magnetic tape recording, the quality of the recorded signal depends on the uniformity of the magnetic coating of the tape. If its sensitivity varies on the tape, the signal level will be reduced periodically, and these reductions in level are called dropouts, their combined effects resulting in an increased noise level in the reproduced signal. See asperity, calendering. In a digital recording, a dropout is caused by an irrecoverable data error.
(2) In timecode, a loss of sequence in the linear timecodetime code count.