JPH10308065A - Recording and reproducing method and device for digital signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately reproduce a digital video signal which is time- compressed and recorded by time-expanding the signal with simple configuration in the method and device for reproducing the time-compressed digital signal by scanning the signal surface of a magnetic tape into the magnetic tape while running the magnetic tape, or reproducing the time-compressed digital signal from the magnetic tape. SOLUTION: A control circuit 7 controls running of a magnetic tape 10 while writing the compressed digital signal reproduced from the magnetic tape 10 in a memory 9, when the signal is written in the memory 9 by the prescribed limit capacity, after the magnetic tape 10 is made to run in the reverse direction by fixed quantity, stopped temporarily, operation for restarting running of the magnetic tape 10 is repeated at the point of time when the prescribed empty capacity is caused in the memory 9 by reading out the compressed digital signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for scanning a signal surface of a tape-shaped recording medium such as a digital video tape recorder while running the recording medium in a longitudinal direction, and recording a time-compressed digital signal on the recording medium. Or a method and apparatus for reproducing a time-compressed digital signal from the recording medium.

[0002]

2. Description of the Related Art With the development of digital information transmission technology such as satellite broadcasting, cable TV, and the Internet in recent years, multimedia information such as digital video signals can be directly sent to households without using a medium such as a cassette tape. The service to deliver is feasible.

In such a service, for example, a digital video signal to be delivered to each home is time-compressed and transmitted. In each home, a received digital video signal is converted into a time-compressed bit stream. It is possible to perform azimuth recording on a cassette tape by a helical scan type digital video tape recorder. At the time of signal reproduction, a cassette tape is reproduced, and a compressed digital video signal obtained by this is subjected to time expansion, demodulation, D / A conversion, etc., to generate an analog video signal, which is supplied to a TV receiver. And restore the video. For the time compression of the digital video signal, for example, a fractal compression method (Nikkei Byte, March 1997 No. 321)
Page to page 325), whereby a video of about 2 hours can be compressed to about 5 minutes and recorded on a cassette tape.

The following two methods are conceivable as a method of reproducing a time-compressed digital video signal by extending the time. That is, the tape running speed during reproduction is uniformly reduced according to the compression ratio. After running the tape for one frame (for example, one track) at the same speed as the signal recording, the intermittent feeding operation for temporarily stopping is repeated, and the tape running speed during reproduction is reduced as an average value.

[0005]

However, in the above method, the tracing angle of the magnetic head differs from that at the time of signal recording due to a decrease in the tape running speed. The tracing angle must be changed, which requires a complicated mechanism. Further, in the above method, the tape must be run and paused frequently at an extremely short pitch, and during a certain period immediately after the start of the running after the pause, the running speed of the tape is not stable. There is a possibility that signal reproduction may not be performed accurately.

Accordingly, a first object of the present invention is to provide a digital signal recording / reproducing method and apparatus capable of reproducing a time-compressed digital video signal by time-expanding with a simple configuration. . A second object of the present invention is to provide a digital signal recording / reproducing method and apparatus capable of accurately reproducing a time-compressed digital video signal when performing time-expanded reproduction.

[0007]

SUMMARY OF THE INVENTION A digital signal recording / reproducing method and apparatus according to the present invention scans a signal surface of a tape-shaped recording medium while running the recording medium in a longitudinal direction, and outputs a time-compressed digital signal. Is recorded on a recording medium, or to reproduce a time-compressed digital signal from the recording medium, while writing the compressed digital signal reproduced from the recording medium to the memory, while controlling the running of the recording medium, When the memory is written to the predetermined limit capacity, the operation of temporarily stopping the running of the recording medium and resuming the running of the recording medium when a predetermined free space is generated in the memory by reading the compressed digital signal is repeated. Specifically, at the time of signal reproduction, the recording medium is caused to run at the same speed as at the time of signal recording. When the digital signal is a video signal, the memory has a capacity capable of storing at least several frames of video signals.

In the recording and reproducing method and apparatus according to the present invention, a time-compressed digital signal is written on a recording medium by setting and executing a signal recording mode. Then, when the signal reproduction mode is set, the reproduction of the signal by running and scanning of the recording medium is started, and the writing of the compressed digital signal obtained by this to the memory is started. When a signal read request is issued from the subsequent circuit to the memory, a compressed digital signal is read from the memory, and the signal is supplied to the subsequent circuit and subjected to necessary processing such as time expansion, for example. Image display is started. Here, the reading of the signal from the memory is performed at a lower speed than the writing speed of the signal, so that the signal-written area of the memory gradually expands.

Thereafter, when the memory is written to a predetermined limit capacity, the running of the recording medium is temporarily stopped. As a result, only reading of the compressed digital signal from the memory is continued, and the free space of the memory gradually increases. Then, when a predetermined free space occurs in the memory, the running of the recording medium and the writing of the compressed digital signal to the memory are restarted. By repeating the above operation, the digital signal which is time-compressed and recorded on the recording medium is sequentially output to the subsequent circuit at a frequency corresponding to the compression ratio, and time-expanded.

In the specific configuration of the recording / reproducing method and apparatus according to the present invention, when the memory is written to a predetermined limit capacity, the recording medium is caused to travel in a reverse direction by a fixed amount and then temporarily stopped. As a result, a certain amount of overlap is given on the recording medium every time the direction of travel is changed in scanning during signal reproduction.

In this specific configuration, immediately after the forward running of the recording medium is started after the recording medium is temporarily stopped, even if the running speed of the recording medium is unstable, the forward step is performed in the previous step. By the time the vehicle travels to the position where the vehicle has stopped, that is, the speed is stabilized in the overlap section,
After the reproduction of the overlap section is completed, in a new reproduction section following this, signal reproduction is performed at a stable running speed.

[0012]

According to the digital signal recording / reproducing method and apparatus according to the present invention, for example, the same operation as that of a conventional video tape recorder, that is, reproduction by forward tape feed, reverse tape feed, and thereafter. The signal reproduction and the time expansion are performed by the temporary stop, so that a special mechanism is not required for the reproduction of the time-compressed digital video signal, and the configuration is simple. In addition, according to the specific configuration for providing overlap to the scanning of the recording medium, in the reproduction of the time-compressed digital video signal, the signal is reproduced at a stable running speed. It will be accurate without any.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a digital video signal distribution system according to an embodiment of the present invention. As shown in FIG. 1, a digital video signal distribution system according to the present invention
It comprises (1) and a receiving device (2), and a receiving device (3) having a display is connected to the receiving device (2). The compressed digital video signal distributed from the distribution station and received by the receiving device (2) is sent to the digital signal recording / reproducing device (1) and recorded on the magnetic tape (10). Thereafter, the compressed digital video signal reproduced from the magnetic tape (10) is supplied to the receiving device (2), subjected to necessary processing such as time expansion, and output to the receiver (3). The display is performed.

The digital signal recording / reproducing apparatus (1) has the same configuration as a conventional helical scan type digital VTR, and performs a driving operation of a magnetic tape (10) and a rotation driving of a magnetic head (4). VTR mechanism (5), a head amplifier (6) for amplifying a recording signal and a reproduction signal by the magnetic head (4), a control circuit (7) for controlling the VTR mechanism (5), and a control circuit (7) An input key (8) for giving various commands to the memory, and a memory having a storage capacity for a plurality of frames and used for signal reproduction processing as described later.
(9). Here, the control circuit (7) and the memory
(9) forms a characteristic configuration of the present invention, and its operation will be described later.

On the other hand, the receiving device (2) is configured to receive a digital video signal that has been time-compressed by a fractal compression method or the like, and is transmitted using, for example, a satellite broadcast wave. A receiving circuit that receives a compressed digital signal and supplies it to the digital signal recording / reproducing device (1)
(12) A signal read command R is issued to the memory (9) of the digital signal recording / reproducing apparatus (1), and the digital video signal D read in accordance with the command is time-expanded, demodulated, and D / A converted. Decompression / demodulation circuit (1
The analog video signal output from the decompression / demodulation circuit (11) is output to the receiver (3).

In the above digital video signal distribution system, when the signal recording mode is set by operating the input key (8), the VTR mechanism (5) operates to drive the magnetic tape (10) at a constant speed. At the same time, the magnetic head (4) is driven to rotate. Also, the compressed digital video signal received by the receiving device (2) is supplied to the magnetic head (4) through the head amplifier (6) of the digital signal recording / reproducing device (1), and the running of the magnetic tape (10) is performed. Azimuth recording is performed on the signal surface of the magnetic tape (10) by helical scanning by rotation of the magnetic head (4). Here, the compressed digital video signal can be time-compressed on a real time axis from a signal of about 2 hours to a signal of about 5 minutes.
Minutes will be recorded over a tape length equivalent to minutes.

Thereafter, when the signal reproduction mode is set by operating the input key (8), the VTR mechanism (5) operates, and the magnetic tape (10) is driven to run at the same speed as that for signal recording. The magnetic head (4) is driven to rotate at the same speed as during signal recording. Thereby, the magnetic head (4)
The compressed digital video signal obtained from the head amplifier (6)
Is written to the memory (9). At this time, magnetic tape
The running of (10) and the writing of the compressed digital video signal to the memory (9) are controlled by the control circuit (7) as described later. The compressed digital video signal written in the memory (9) is sequentially read out according to a signal read command R input from the decompression / demodulation circuit (11) of the receiving device (2), and the decompression / demodulation circuit (11) Supplied to

FIG. 2 shows the digital signal recording / reproducing apparatus.
The control procedure in the signal reproduction mode executed by the control circuit (7) of (1) is shown. First, it is determined in step S1 whether a command to set the signal reproduction mode has been input, and if yes, the signal reproduction mode is set in step S2. Next, in step S3, it is determined whether or not the memory is in a "memory full" state in which the memory has been written up to a predetermined limit capacity. Here, when the determination is no, the signal reproduction is continued. In this process, when a signal read command is input from the receiving device (2), the compressed digital video signal written in the memory is read. Since reading of the digital video signal from the memory is performed at a low frequency in accordance with the compression ratio of the digital video signal, writing of the digital video signal to the memory proceeds faster, and writing of the memory (9) proceeds. The completed area gradually expands.

Thereafter, when the determination is YES in step S3, the process proceeds to step S4, in which rewind reproduction for a plurality of frames is executed, and then pause is performed in step S5. As a result, the magnetic tape is rewound by a certain amount. It should be noted that the video signal obtained by rewind reproduction is used only for tape rewind control, and is not used for writing to a memory or displaying a video. Therefore, only reading of the digital video signal from the memory is performed, and the writable area of the memory is gradually expanded.

Subsequently, in step S6, it is determined whether or not the memory has entered a "memory empty" state in which a predetermined free space has been generated. Thereafter, if the result of the determination in step S6 is YES, the process returns to step S2, where the reproduction mode is set, and the writing of the compressed digital video signal to the memory is continued.

According to the control procedure described above, the tape is rewound by a fixed amount each time the memory becomes full, and reproduction in the forward direction is started again from the rewind position. Each turn will give a certain amount of overlap on the tape. In this overlap section, since the tape has just started running,
Although the running speed is unstable and an error may occur in signal reproduction, the speed is stabilized by the end of the overlap section. The signal is reproduced by the speed. Therefore, of the digital video signals obtained by the two scans in the overlap period, the signal obtained by the first scan is adopted, and the signal obtained by the second scan is invalidated, so that there is no error. An accurate reproduction signal can be obtained.

FIG. 3 shows that by executing the above control procedure,
This shows how a digital video signal recorded on a tape after being time-compressed is time-expanded and reproduced. The start time t1 = 0 and the end time t2 = T as shown in FIG.
The current video signal before compression is time-compressed at a predetermined compression rate and recorded in areas p1 and p2 on the magnetic tape as shown in FIG.

As shown in FIG. 3C, by the above-mentioned running control, first, in a step, the video signal is sequentially written to the memory as shown in FIG.
Thereby, the video signal D of the first recording area A on the tape is
When 1 is written into the memory and the memory becomes full, the tape is rewound by a fixed amount in step and temporarily stopped. Thereafter, when the memory becomes empty, the video signal is sequentially written to the memory while the tape is caused to run in the forward direction again in step. As a result, the video signal D2 of the next recording area B on the tape is written into the memory, and when the memory is full, the tape is rewound by a certain amount in a step and is temporarily stopped. Thereafter, when the memory becomes empty, the video signal is sequentially written to the memory while the tape is caused to run in the forward direction again in step. As a result, the video signal D3 of the last recording area C on the tape is written to the memory.

In this manner, each of the recording areas A,
After a series of digital video signals recorded in B and C are once written in the memory, they are read out at a frequency corresponding to the compression ratio, and subjected to time expansion according to the compression ratio. )
As a result, a reproduced signal at the start time t1 = 0 and the end time t2 = T is obtained.

As described above, according to the digital video signal distribution system of the present invention, the digital signal recording / reproducing apparatus (1)
In the signal reproduction mode, the same tape running speed as that in the signal recording mode can be set. Therefore, a special mechanism for matching the trace angles is not required, and a VTR mechanism having exactly the same configuration as the conventional one should be used. Can be done. In addition, since the memory has a storage capacity for a plurality of frames, the frequency of tape pauses during signal reproduction is low. By providing the lap section, errors during signal reproduction are avoided, so that high-quality reproduced video can be obtained.

The configuration of each part of the present invention is not limited to the above embodiment, and various modifications can be made within the technical scope described in the claims. For example, it goes without saying that the target of recording and reproduction is not limited to a video signal, but may be an audio signal or another data signal.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a digital signal recording / reproducing device and a receiving device according to the present invention.

FIG. 2 is a flowchart showing a control procedure in signal reproduction of the digital signal recording / reproducing apparatus.

FIG. 3 is a time chart for explaining the signal reproducing operation.

[Explanation of symbols]

 (1) Digital signal recording / reproducing device (2) Receiving device (3) Receiver (4) Magnetic head (5) VTR mechanism (6) Head amplifier (7) Control circuit (8) Input key (9) Memory (10) Magnetic tape (11) Decompression / demodulation circuit (12) Receiving circuit

Claims (6)

[Claims] 1. A method for scanning a signal surface of a tape-shaped recording medium while moving the tape-shaped recording medium in a longitudinal direction to record a time-compressed digital signal on the recording medium, or a method for time-compressed digital signals from the recording medium. A method of recording and reproducing a digital signal for reproducing a signal, wherein while writing a compressed digital signal reproduced from a recording medium to a memory, while controlling the running of the recording medium, when the memory is written to a predetermined limit capacity, A digital signal recording / reproducing method, wherein the operation of resuming the running of the recording medium is repeated when a predetermined free space is generated in the memory by reading the compressed digital signal and suspending the running of the recording medium. 2. When the memory is written to a predetermined limit capacity, the recording medium is driven in a reverse direction by a fixed amount,
2. The digital signal recording / reproducing method according to claim 1, wherein the digital signal is temporarily stopped. 3. The digital signal recording / reproducing method according to claim 1, wherein at the time of signal reproduction, the recording medium is run at the same speed as at the time of signal recording. 4. A tape traveling / scanning system for scanning a signal surface of a recording medium while traveling the tape-shaped recording medium in a longitudinal direction, a signal recording system for recording a time-compressed digital signal on the recording medium, A signal reproducing system for reproducing a time-compressed digital signal from a recording medium, a memory for storing a compressed digital signal reproduced from the recording medium, and a control system for controlling running of the recording medium and signal writing to the memory. Digital signal recording and reproducing device, wherein the control system comprises:
While writing the compressed digital signal reproduced from the signal surface of the recording medium to the memory, the running of the recording medium is controlled, and when the memory is written to a predetermined limit capacity, the running of the recording medium is temporarily stopped, and the compressed digital signal is written. A digital signal recording / reproducing apparatus which repeats an operation of restarting the running of a recording medium when a predetermined free space is generated in a memory by reading a signal. 5. The digital signal recording / reproducing apparatus according to claim 4, wherein the control system causes the recording medium to travel a predetermined amount in the reverse direction and then pause when the memory has been written to the predetermined limit capacity. 6. The control system according to claim 4, wherein the control system causes the recording medium to run at the same speed during signal reproduction as during signal recording.
A digital signal recording / reproducing device according to claim 1.