Dynamic magnetic information storage or retrieval – General processing of a digital signal – Data in specific format
Reexamination Certificate
1999-12-22
2001-03-13
Edun, Muhammad (Department: 2753)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Data in specific format
C360S053000, C360S039000, C369S059160
Reexamination Certificate
active
06201654
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method and an apparatus for recording, on a recording medium such as a magnetic tape, a received signal of a digital broadcasting or a digital output signal from another digital video tape recorder.
In digital television broadcasting, a digital signal which has gone through an information compression process is transmitted. For efficient use of the transmission line, the transmission rate of the digital signal differs with the kinds of video sources, and even in the transmitted digital signal of the same image source, the transmission rate varies from moment to moment.
The digital video tape recorder converts an analog video signal into a digital signal, and records the video signal on a magnetic tape in the form of a digital signal. The transmission rate of the output digital signal of the digital video tape recorder differs from the transmission rate of the transmitted signal of digital television broadcasting.
A digital signal recording apparatus for recording a compressed digital video signal on a magnetic tape with a rotary head is revealed in Japanese Patent Application Laid-Open No. JP-A-5-174496.
Apparatus for recording on a recording medium a compressed digital signal in which the transmission rate and the data intervals are unfixed has not been developed. Nor has a recording method been developed which can selectively record signals of different transmission rates in a single recording apparatus.
A home use digital video tape recorder for recording a compressed digital video signal on a magnetic tape with a rotary head is reported in pages 137 to 150 of “Data Compression and Digital Modulation” published by Nikkei BP. This home use digital video tape recorder uses a high-performance metal-evaporated tape on a special-purpose cassette, and records a compressed digital video signal of 24.948 Mbps and digital audio signals of two channels (1.536 Mbps) at the head rotating speed of 9,000 rpm and at the recording rate of 41.85 Mbps. Signals of such high transmission rates cannot be recorded by the prior art on a conventional analog VTR in general use. The reason is that since the rotary head speed of the analog signal VTR is 1,800 rpm and an oxide tape is used, it is difficult to record a digital signal at a recording rate of 20 Mbps or higher. In addition, the cassette for the analog VTR is in a shape different from that of the digital VTR written in the above-mentioned literature.
SUMMARY OF THE INVENTION
An object of the present invention is to provide digital signal recording method and apparatus for recording a compressed digital video signal in which the data transmission rate and the data intervals are unfixed as in digital television broadcasting, for example.
Another object of the present invention is to provide digital signal recording method and apparatus capable of recording signals different in the transmission rate and in the format of recording signal, such as the packet size on a single apparatus.
Yet another object of the present invention is to provide digital signal recording method and apparatus for recording a digital signal of a high transmission rate on an ordinary analog signal VTR.
According to an aspect of the present invention, a digital signal of a format in which fixed-length packets are arranged at irregular intervals is added with time information specifying to each packet an interval relative to the adjacent packet, the digital signal added with time information is recorded on a recording medium, the digital signal added with time information is reproduced from the recording medium, and the digital signal is output so that the packets of the reproduced digital signal are arranged at fixed intervals on the basis of the time information.
According to another aspect of the present invention, the digital signal is divided into pieces of data of a specified data length, and blocks are generated by adding a synchronizing signal, control signals and an error correcting code to each of the pieces of data, and a specified number of blocks are recorded in each signal recording unit area on the magnetic recording medium. The control signal added to each block includes a first control signal showing the operation mode when the block was recorded and a second control signal showing the contents of the digital signal recorded in the signal recording unit area.
According to a further aspect of the present invention, each block is generated by adding a sync signal, control signals and an error correcting code to m bytes (m is a positive integer) of digital signal of a packet type in which a packet is formed by n bytes (n is a positive integer) of data, and a specified number of blocks are recorded in each signal recording unit area on a magnetic recording medium. And, the values of n and m are set so that n:m=n′:m′ (where n′<n and m′<m), and m′ packets are arranged in n′ blocks, and recorded on the recording medium.
According to yet another aspect of the present invention, each block is generated by adding a sync signal, control signals and an error correcting code to m bytes (m is a positive integer) of digital signal of a packet type in which a packet is formed by n bytes of data (n is a positive integer), and a specified number of blocks are recorded in a signal recording unit area on a magnetic recording medium. And, the control signal includes information for identifying the value of the above-mentioned number n of bytes of a packet.
According to a still further aspect of the present invention, there is provided a recording apparatus for simultaneously recording signals on a plurality of tracks by a plurality of rotary heads, wherein a digital signal is divided into data units of fixed data lengths, a sync signal, control signals and an error detecting and correcting code are added to each of the data units to thereby change said data units into blocks, and a specified number of said blocks are recorded on a recording area on a track of a magnetic recording medium by said rotary heads, wherein each said rotary head includes at least four magnetic heads, and wherein at least a first digital signal of 25 Mbps and a second digital signal of 1.6 Mbps are recorded simultaneously by two magnetic heads, each operating at a recording rate of 20 Mbps or less.
Other objects and effects of the present invention will become apparent by reading the following description with reference to the accompanying drawings.
REFERENCES:
patent: 5224087 (1993-06-01), Maeda et al.
patent: 5768298 (1998-06-01), Nagai et al.
patent: 5-174496 (1993-07-01), None
“Data Compression andn Digital Modulation,” Nikkei BP, pp. 137-150.
Hosokawa Kyoichi
Noguchi Takaharu
Okamoto Hiroo
Owashi Hitoaki
Edun Muhammad
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Hitachi , Ltd.
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