Digital VTR

Details Digital VTR Digital VTR

1999-03-24

2004-07-20

Tran, Thai (Department: 2615)

Motion video signal processing for recording or reproducing

Local trick play processing

With randomly accessible medium

C386S349000

Reexamination Certificate

active

06766105

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a digital VTR for subjecting input image data to variable length compression to record variable length coding data on a video tape so that the number of fields and the number of tracks composing the recorded variable length coding data are not in a linear relationship.
2. Description of the Related Art
In a digital VTR (Video Tape Recorder) comprising a conventional image compressing circuit, input image data is subjected to fixed length compression, and coding data obtained is recorded on a video tape, so that the number of fields and the number of tracks composing the recorded coding data are in a linear relationship. In such a digital VTR, the tape running distance obtained from CTL (control) pulses and the number of fields composing an image read out of the video tape are in a linear relationship, thereby making it possible to realize a linear time counter function in which absolute time information or the like is obtained by counting the CTL pulses.
In such a digital VTR, the type running distance obtained from the CTL pulses and the number of fields composing the image read out of the video tape are in a linear relationship, thereby making it possible to record on the video tape a control signal such as a VISS (VHS Index Search System) signal which is a signal for searching for an arbitrary scene or a VASS (VHS Address Search System) signal for recording time required for recording or the like utilizing a CTL signal, as in a conventional analog VTR.
Writing of one CTL signal is performed by first writing the N pole and then writing the S pole after an elapse of a predetermined time period. “0” or “1” can be indicated by the ratio of time required to write the N pole to time required to write the S pole within one period of the CTL signal. The VISS signal is a signal which is a succession of 60 or more “1”. The VASS signal is inserted behind the VISS signal.
The applicant of the present invention has developed a digital VTR adapted so as to subject input image data to variable length compression, and then record as many variable length coding data as possible on one track irrespective of the number of fields. In such a digital VTR, the number of fields and the number of tracks composing the recorded variable length coding data are not in a linear relationship, so that the tape running distance obtained from the CTL pulses and the number of fields composing the image read out of the video tape are not in a linear relationship. Even if the CTL pulses are counted, therefore, it is impossible to realize a linear time counter function. Further, it is impossible to record on the video tape the control signal such as the VISS signal which is a signal for searching for an arbitrary scene or the VASS signal for recording time required for recording or the like utilizing the CTL signal.
Also in the digital VTR developed by the applicant of the present invention, absolute time information can be recorded in a recording track. When the recording track can be completely traced as at the time of normal reproduction, therefore, the absolute time information need not be acquired utilizing the CTL pulses. When the trace is not completely performed, for example, in cases of FORWARD, REWIND, CUE (FORWARD PLAY), REVIEW (REWIND PLAY), and so forth, the absolute time information cannot be taken out.
Also in the digital VTR developed by the applicant of the present invention, the control signal such as information relating to a search for an arbitrary scene or time information can be recorded in the recording track When the recording track can be completely traced as at the time of normal reproduction, therefore, the information relating to a search for an arbitrary scene, the time information, or the like need not be recorded utilizing the CTL signal. When the trace is not completely performed, for example, in cases of FORWARD, REWIND, CUE (FORWARD PLAY), REVIEW (REWIND PLAY), and so forth, however, the control signal such as the information relating to a search for an arbitrary scene or the time information cannot be taken out.
SUMMARY OF THE INVENTION
An object of the present invention is to provide, even in a digital VTR for subjecting input image data to variable length compression to record variable length coding data on a video tape so that the number of fields and the number of tracks composing the recorded variable length coding data are not in a linear relationship, a digital VTR capable of realizing a linear time counter function.
Another object of the present invention is to provide, even in a digital VTR for subjecting input image data to variable length compression to record variable length coding data on a video tape so that the number of fields and the number of tracks composing the recorded variable length coding data are not in a linear relationship, a digital VTR capable of recording a control signal, composed of a binary signal,such as a VISS signalor a VASS signal on a track other than a recording track.
A first digital VTR according to the present invention is characterized by comprising an image compressing circuit for subjecting input image data to variable length compression, to output variable length coding data and identification data representing the end of one field, recording means for recording on a video tape the variable length coding data outputted from the image compressing circuit, and pseudo CTL signal recording means for recording a pseudo CTL signal on the video tape every time the identification data is outputted from the image compressing circuit.
The pseudo CTL signal is recorded on a voice track, for example, which is not used in the digital VTR.
A second digital VTR according to the present invention is characterized by comprising an image compressing circuit for subjecting input image data to variable length compression, to output variable length coding data and identification data representing the end of one field, means for temporarily storing in a first memory the variable length coding data and the identification data which are outputted from the image compressing circuit, time measurement means for measuring a time interval from the time when the previous identification data is outputted from the image compressing circuit to the time when the current identification data is outputted from the image compressing circuit, means for temporarily storing in a second memory information relating to the time interval obtained by the time measurement means, recording means for reading out the variable length coding data and the identification data from the first memory and recording the variable length coding data on a video tape, and pseudo CTL signal recording means for recording on the video tape a pseudo CTL signal capable of representing a binary value on the basis of information obtained from the second memory every time the identification data is read out of the first memory and relating to a time interval between the identification data read out of the first memory and identification data to be subsequently read out of the first memory.
Physically identical memories can be used as the first memory and the second memory. The pseudo CTL signal is recorded on a voice track, for example, which is not used in the digital VTR. A VISS signal and/or a VASS signal, for example, which have been produced utilizing a CTL signal in an analog VTR, are produced by the pseudo CTl signal.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.


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patent: 5457580 (1995-10-01), Yoo
patent: 5583936 (1996-12-01), Wonfor et al.
patent: 5586200 (1996-12-01), Devaney et al.
patent: 5841942 (1998-11-01), Sugiyama
patent: 49-128713 (1974-12-01), None
patent: 3-127364 (1991-05-01), None
Copy of Japenese Patent Office Notice o

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