The present invention generally relates to a video signal record/play-back apparatus and particularly relates to a digital video signal record/play-back apparatus having a function to record/play-back a time code.
In edit of a video tape, it is important to know positions on the editing video tape. At present, in the field of broadcast industry or the like, in order to perform edit of video tapes accurately and efficiently, time codes are recorded on a video tape along its length so that the time codes are used as positional information.
As described in "TIME AND CONTROL CODE FOR VIDEO TAPE RECORDER", IEC STANDARD Publication, 461, 1986, a time code is standardized and has become generally accepted as means for correctly detecting positional information on a tape.
In broadcast stations and so on, recently, the requirement for making picture quality high has become strong as video signals have been made digital and digital-record video tape recorders for business use, etc. have begun to come out. In a digital-record video tape recorder, in order to obtain high functional property and high reliability, an analog video signal is converted into a digital signal, and the thus converted digital video signal is recorded while being subject to digital signal processing such as addition of address data indicating recorded positions of video signal data, addition of parity bits, data shuffling for uniformly distributing data in recording the data, the thus recorded digital video signal being played back through digital signal processing reverse to that performed in recording.
Since it takes much time for performing the above signal processing, a delay time appears remarkably in the signal between a video signal input terminal of an analog-to-digital (A/D) conversion circuit and a recording head in a digital-record video tape recorder when compared with a conventional analog-record video tape recorder.
When video editing is carried out by use of a time code in a conventional analog-record video tape recorder, the time taken for signal processing is negligibly small with respect to both a video signal and a time code signal so that the video signal and time code signal can be recorded/played-back with a timing relationship in agreement with that defined in the time code standard without any trouble. In a digital-recorder video tape recorder, on the contrary, it takes much time for the digital signal processing of a video signal when editing is carried out by use of a time code in the conventional recording system in which the time code is recorded in the longitudinal direction of a video tape, thus being a longitudinal time code, so that the timing relationship in recording the video signal and the time code signal on a video tape and the timing relationship in play-back of those signals may be shifted from predetermined relationships. Accordingly, if dubbing of such a video tape is repeatedly carried out, the shift in timing relationship between the video signal and time code signal to be recorded is multiplied so as to make it difficult to maintain the correspondency between the time code and the video frame scene. Further, in editing by use of a time code, when insert edit of a video signal from a play-back device is performed onto a recorded video tape of a recording device by means of an editing device, a displacement in editing point is caused between a video signal already recorded on the video tape and an input video signal to be newly recorded on the video tape so that those video signals cannot be connected at a designated editing point on the video tape even if the editing device tries to make the respective editing points of the recording device and the play-back device agree with each other at every frame while referring to the respective time codes fed from the recording device and the play-back device.
USPTO Backgrounds
USPTO Backgrounds