| 摘要 |
<p>SO1120 IMPROVED TIME BASE ERROR CORRECTING APPARATUS Improved time base error correcting apparatus of the type wherein time base errors in a video signal, such as a video signal reproduced by a video signal playback device, are corrected. The apparatus includes a main memory into which picture elements contained in each line interval of the video signal are written at a write-in rate that is synchronized with the time base information contained in that video signal, and from which the picture elements are read out at a reference rate. A drop-out detector detects drop-out conditions which may occur in the video information and synchronizing information portions of the video signal. Drop-out indications are stored in a drop-out condition memory so as to represent the positions within a line interval that dropout has occurred. These drop-out indications are written into and read out of the drop-out condition memory in synchronism with the writing in and reading out of picture elements from the main memory. Each picture element read out from the main memory is supplied to a drop-out compensator which is responsive to a read out drop-out indication to replace a dropped out picture element that is read out from the main memory with the picture element which had been in the same relative position in the immediately preceding line interval. A velocity error correcting device also is provided in order to correct velocity errors which may be present in each line interval. In the event that a velocity error cannot be detected, for example, because drop-out has occurred in the synchronizing portion of a line interval, the velocity error which had been detected for the previous line interval is used again in this and then the next-following interval, i.e., for a total of three -i-consecutive line intervals. An offset voltage is added to the velocity error correcting operation for this third line interval, except that this offset voltage is subtracted during a drop-out compensating operation in that third line interval. -ii-</p> |
