Comb Filter Improvement with Spurious Chroma Deletion
The problem of uncancelled or spurious chroma in a luminance signal can now be effectively eliminated. This common problem arises when (1) delay-line comb filters are used to separate the luminance and chrominance from an NTSC-encoded color television signal and (2) video changes over three successive TV lines at frequencies above about 2.5 MHz are not negligible. The most noticeable effect is the appearance of scintillating serrations along horizontal edges where vertical hue or saturation changes have occurred. To delete spurious chroma from the luminance signal, a detection circuit has been devised which can determine when chrominance transitions are occurring in the vertical direction. When such transitions are detected, a gate is generated which causes the luminance signal to be suitably filtered, thereby eliminating the spurious chroma that otherwise would have appeared. The gated filtering of chroma is controlled by a manually adjustable threshold so that chroma deletion can be utilized at as low a chrominance differential level as is permitted by the existing signal-to-noise ratio. Experience with this device in actual operations has been most satisfactory.
- Print ISSN
- 0036-1682
- Published
- 1977-01
- Content type
- Original Research
- DOI
- 10.5594/J06784