Overmodulation distortion occurs when source material has
been videotaped with the videotape recording gain set too high. This type of
distortion is rarely seen these days, as most video equipment now has
overmodulation protection built in. Nonetheless, it is still occasionally seen
when old videotapes are transferred to DVD. It is the video equivalent of having
the recording level set too high when making an audio tape recording. It
manifests itself as horizontal lines of distortion emanating from dark-to-bright
transitions.
Frank Sinatra-Ol' Blue Eyes Is Back (28:12)
Close up of Gene Kelly's shirt - note the lines of distortion emanating from
the left edge of his tuxedo. Contrast this to the right side which is clear of
this artefact.