Digital transmission signal processing system and recording/reproducing system

#The present invention relates to a system for transmitting a digital video signal and recording the received video signal. More particularly, the present invention relates to great extension of the range of use of a digital signal recording/reproducing system by greatly shortening a recording time through transmission of a video signal in a compressed form, and further relates to great extension of the range of use of a digital signal recording/reproducing system by making the number of signals to be recorded and a recording/reproducing time variable.

#As a digital magnetic recording/reproducing system (hereinafter referred to as VTR) is conventionally known, for example, a D2 format VTR. In such a conventional digital VTR, the elongation or shortening of a reproducing time is possible by using variable-speed reproduction. However, the prior art reference does not at all disclose high-speed recording in which a recording time is shortened to 1/m, multiple recording in which a plurality of signals are recorded, and the compression/expansion of a recording/reproducing time.

#The above-mentioned conventional digital VTR has a feature that a high quality is attained and there is no deterioration caused by dubbing. However, the shortening of a dubbing time is not taken into consideration. Therefore, for example, in the case where a two-hour program is to be recorded, two hours are required. Thus, there is a drawback that inconveniences are encountered in use. Also, the multiplexing of recording signals is not taken into consideration. Therefore, for example, when two kinds of programs are to be simultaneously recorded or reproduced, two VTR's are required. This also causes inconveniences in use.

#FIG. 1 is a block diagram of a digital transmission signal processing system and a recording/reproducing system according to an embodiment of the present invention;

#FIG. 2 is a block diagram of a recording/reproducing system according to another embodiment of the present invention;

#FIG. 3 is a diagram for explaining the conventional parity adding method;

#An embodiment of the present invention will now be explained by use of FIG. 1. In the figure, reference numerals 1 and 40 denote magnetic tapes, numerals 2, 3, 41 and 42 magnetic heads, numerals 4 and 43 cylinders, numerals 5 and 44 capstans, numerals 10 and 50 servo control circuits, numerals 20, 31 and 60 demodulation circuits, numerals 21, 32 and 61 error correction circuits, numerals 22 and 23 compression circuits, numerals 24 and 33 parity addition circuits, numerals 25 and 34 modulation circuits, numerals 26 a transmission circuit, numeral 27 a transmission path, numeral 30 a reception circuit, numerals 62 and 63 expansion circuits, numerals 64 and 65 D/A conversion circuits, numeral 70 a video signal output terminal, and numeral 71 an audio signal output terminal.

#Firstly, the operation of a transmission signal processing system will be explained. Digital video and audio signals recorded on the magnetic tape 1 are reproduced by the magnetic heads 2 and 3 mounted on the cylinder 4 and are inputted to the demodulation circuit 20. The magnetic tape 1 travels by virtue of the capstan 5. The travel speed of the magnetic tape 1 and the rotation frequency of the cylinder 4 are, for example, ten times as high as the tape travel speed and the cylinder rotation speed upon normal reproduction. Accordingly, the signal inputted to the demodulation circuit 20 is a signal time-compressed to one tenth. For example, a 120-minute signal recorded on the magnetic tape 1 can be reproduced in 12 minutes.

#Generally, in the case where a digital signal is to be recorded on a magnetic recording medium, the signal is recorded after having been modulated into scrambled NRZ code, M.sup.2 code or the like. The demodulation circuit 20 performs a demodulation processing, that is, a signal processing for restoring the thus modulated signal into original digital data. The signal demodulated by the demodulation circuit 20 is inputted to the error correction circuit 21 in which erroneous data produced in a magnetic recording/reproducing process is detected and the correction for the erroneous data is made. Further, the signal is separated into a video signal and an audio signal which are in turn inputted to the compression circuits 22 and 23, respectively. The video signal is bit-compressed through, for example, discrete cosine conversion. The audio signal is bit-compressed through, for example, non-linear quantization or differential PCM. As a result, the transmission rate of the video signal and the audio signal in total is reduced to, for example, one twentieth.