Hitachi, Ltd.

Other

Yasufumi Yumde

Takashi Furuhata

Takao Arai

Takaharu Noguchi

Michio Masuda

Masaharu Kobayashi

Nobutaka Amada

Kuniaki Miura

Hiroyuki Kimura

Atsushi Yoshioka

Hiroaki Takahashi

Katsuo Mohri

Hiroaki Nabeyama

Toshifumi Shibuya

Toshimichi Terada

Tadashi Takamiya

Kotaro Kawamura

Kazunori Kotani

Fujio Okamura

Takao Aria

In an information recording/reproducing apparatus for recording/reproducing a digital audio signal on/from a magnetic medium, a modulator/demodulator for modulating/demodulating the digital signal by offset quadrature phrase shift keying (O-QPSK). This technique is particularly applicable to the multi-layer recording of video and audio signals in a video tape recording/reproducing system and has the advantage of avoiding interference between the recorded digital audio and video signals at the time of reproduction.

Magnetic recording/reproducing method and apparatus

A PCM audio signal recording and reproducing apparatus samples an audio signal with a sampling frequency having an asynchronous relation to a field frequency of a video signal; converts it to a PCM signal, adds error detection/correction data to a predetermined number of PCM data, forms a data frame by those signals, modulates it in accordance with a predetermined modulation system, and records the audio signal together with the video signal or just the audio signal on a record medium by using a rotary head type scanner which is controlled so as to have a synchronous relation to the field frequency of the video signal. A digital signal processing circuit having a memory of a predetermined capacity is provided, and the number of digital data to be recorded in one data frame is varied in accordance with a difference between the number of input data of the digital audio signal to the digital signal processing circuit and the number of output data supplied to the record medium for recording. In the recording mode, the PCM audio signal is sectioned into blocks, a data block address signal is added to each block to indicate a relative order of a block to the other blocks and is completely added in one track, certain number of blocks are combined to form a block set for processing signals, and an identification signal completing in the block and an interleave block address signal for indicating a relative order to other blocks are added to each block.

Method and apparatus for PCM recording and reproducing an audio signal

A method of producing a tracking control signal in a rotary head type magnetic recording and reproducing apparatus and a rotary head type magnetic recording and reproducing apparatus capable of a proper tracking by the use of the tracking control signal. First and second tracking signals are recorded on local portions of each odd-numbered track and the first tracking signal and a third tracking signal are recorded on local portions of each even-numbered track in such a manner that the second tracking signals on two odd-numbered track adjacent to any one even-numbered track are not overlapped with each other and the third tracking signals on two even-numbered tracks adjacent to any one odd-numbered track are not overlapped with each other when viewed in a direction perpendicular to the longitudinal direction of the tracks; upon scanning of a track crosstalk signals are detected from two adjacent track simultaneously with reproduction of the first and second or third tracking signals; and the detected crosstalk signals are compared by the use of timing of the reproduction of the first tracking signal for each track thereby producing a tracking control signal. The second tracking signal may have a frequency equal to that of the third tracking frequency.

Rotary head type magnetic recording and reproducing apparatus and method

Disclosed is a VTR of the helical scan type having a plurality of rotary magnetic heads. This VTR can select one of a first and a second signal recording forms which are different from each other, and record signals on a magnetic tape. In the first recording form, a frequency-modulated video signal including a luminance signal and a color signal and a frequency-modulated sound signal are recorded on the same track so as to be superimposed one on the other. In the second signal recording form, a frequency-modulated luminance signal and a frequency-modulated color signal are recorded separately on tracks adjacent to each other. This VTR has compatibility with respect to the recording/reproducing of two different signals.

VTR having magnetic-head array capable of recording/reproducing signals

The recording area of the magnetic tape is divided into a first area for recording a PCM converted audio signal and a second area for recording a PCM converted video information. In recording the audio signal and the video information which have been separately PCM converted, the magnetic tape is wrapped around the rotary heads so that a wrap angle of each of said first and second areas is less than 90.degree. with respect to the rotary heads of a predetermined diameter.

Rotary head type PCM recorder

In receiving a narrow band video signal transmitted through a narrow band transmission line such as a telephone line, a sound tape recorder or the like, the narrow band video signal is first stored in memories and is then read out therefrom at a higher reading-out speed than the writing-in speed so that the band allocated to the read-out signal is broadened to facilitate the display of the video signal. When reading out the video signal from the memories, the timing of reading out even lines constituting a display image of the video signal is shifted from the timing of reading out odd lines constituting the same display image by a time substantially equal to half the reciprocal of the frequency in terms of the bandwidth of the read-out video signal, the reciprocal corresponding to the resolution limit for the received video signal.

Method of receiving a video signal

A method for transmitting a color video signal on a narrow-band transmission line such as a telephone line or an audio tape recorder is disclosed. The carrier frequency is so reduced that no clock signal of high frequency is used. The carrier chrominance signal and the brightness or luminance signal are transmitted separately in time-division multiplication thereby to eliminate color distortion. The write clock signal frequency for the carrier chrominance signal is rendered inversely proportional to the product of a given number determined by the number of samples required for faithful transmission of the carrier chrominance signal and a multiple enabling the carrier frequency to be minimized. The read clock signal frequency for the carrier chrominance signal is reduced to one over an integer of the luminance signal, so that the carrier chrominance signal is read at intervals of the integer in order of storage in a memory. At the time of writing the color chrominance signal in the memory, the write clock frequency therefor is rendered equal to the write clock frequency for the luminance signal. Thus the capacity of the memory for the carrier chrominance signal is one over an integer of that for the luminance signal.

Method for transmitting a color video signal on a narrow-band

A horizontal synchronizing signal contained in a composite video signal undergoing a phase fluctuation is phase modulated and substituted for the original horizontal synchronizing signal. The phase modulation of the horizontal synchronizing signal of the input signal is effected at a phase modulation circuit and then the phase modulated signal is applied to an AFC circuit unit which has the same transfer characteristic as that of a horizontal AFC circuit of an ordinary television receiver set. The phase modulation circuit is controlled by a signal in response to a phase difference between the output of the AFC circuit unit and the original horizontal synchronizing signal. A composite video signal containing the horizontal synchronizing signal subjected to the phase modulation in this manner is applied to the television receiver set, thereby displaying a picture image free from the fluctuation.

System for compensating jitter of video signal

A signal multiplexing method and system for transmitting a television signal by a narrow-band transmission medium incapable of transmitting d.c. components. In this method, a two-polarity pulse train signal consisting of pulses of alternately inverted polarities is subject to pulse modulation by the video information only of the television signal. The horizontal and vertical synchronizing signals indicative of the beginning of a line, field or the like are coded in such a form that some of the successive pulses in the pulse train signal have the same polarity.

Method and system for multiplexing signal for transmission

There is provided a receiving system for receiving the video signal for each one frame. The video signal is divided into line signals each corresponding to the horizontal scanning period and transmitted sequentially in such a manner that each line signal is inserted in a television signal during each vertical blanking period. The line signals inserted in the transmitted television signal are separated therefrom and the separated line signals are selectively recorded on the odd and even field tracks of a rotary recording medium. Switches for selectively recording the line signals on the even field and odd field tracks are controlled by the output of an odd/even field selection signal generating circuit. The number of revolutions of the rotating recording medium is determined so that the line signals selectively recorded on the even field and odd field tracks of the rotating recording medium are arranged in the correct order and without leaving any spaces between the line signals or causing the line signals to overlap with each other. When the video signals for one frame have been recorded on the rotating recording medium, the one-frame video signals recorded on the rotating recording medium are repeatedly read out to reproduce a still picture.

Receiving system for auxiliary information signal transmitted during the

A system for converting a broad-band picture signal into a narrow-band signal or converting a narrow-band picture signal into a broad-band signal comprising a first memory means which has a capacity of storing a picture signal corresponding to one frame and can record and reproduce a broad-band picture signal at the same speed as the transmitted speed, and a second memory means which has a capacity of storing a picture signal corresponding to one scanning line and is such that writing speed and reading speed can be freely varied. In broad-to-narrow conversion, a broad-band picture signal corresponding to one frame is stored in the first memory means and is read out repeatedly from the first memory means at a speed equal to the speed with which a picture signal is commonly transmitted, and individual line signals appearing from the first memory means are successively written in the second memory means at a suitable time interval and are read out from the second memory means at a low speed corresponding to the desired frequency band. In narrow-to-broad conversion, individual line signals of a broad-to-narrow converted picture signal are successively written in the second memory means at a low speed and are read out therefrom at a high speed to be written in the first memory means, and after the signal corresponding to one frame is written in the first memory means according to the order of the scanning lines, this signal is read out from the first memory means to provide a broad-band picture signal. A plurality of second memory means may be provided so as to improve the efficiency in respect of time of transfer of the signal from the first to the second memory means or from the second to the first memory means and to reduce the period of time occupied by the broad-to-narrow converted frame signal.

Growing community of inventors

Yokohama, Japan

Yasufumi Yumde