Digital Time-Base Correction for Video Signal Processing
Recent advances in digital television are exemplified in the techniques now available for processing and correcting the errors that arise when videotape is played back with a VTR. Such techniques use time-base correctors (TBCs) in systems for eliminating VTR distortions. A short history of time-base correction is given, from the delay-line units used 20 years ago with quadruplex VTRs to the latest digital TBCs that can reduce large time-base errors of helical-scan VTRs virtually to invisibility. Principles and details of the Microtime 640 Digital TBC are discussed. Briefly, it operates in either the V/H-lock or no-lock mode. Either direct or heterodyne color recovery can be selected. The input signal is sampled at three times the color subcarrier frequency, and 8-bit PCM encoding is used. For speed and simplicity of control, the Model 640 employs a bipolar random-access memory (RAM) of about 24-kbit capacity. Such TBCs can now interface with virtually any VTR, and their use is expected to grow steadily.
- Print ISSN
- 0036-1682
- Published
- 1976-03
- Content type
- Original Research
- DOI
- 10.5594/J06852