JP3209631B2 - Helical scanning type recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a helical scanning type recording / reproducing apparatus, and more particularly, to recording a plurality of types of digital information having substantially the same transmission rate and different temporal axis compression ratios, and transmitting the digital information to a desired transmission. The present invention relates to a helical scanning type recording / reproducing apparatus capable of performing reproduction by extending a time axis in a rate.

[0002]

2. Description of the Related Art With the progress of video (audio) information encoding (digitization) technology and its compression technology, and the development of digital signal processing LSIs represented by microprocessors and digital signal processors, AV systems and communication systems have been developed. In addition, the integration of computer systems has become possible, and a system called multimedia has attracted attention.

In one field of this multimedia, for example,
There is a cable television (CATV). This CATV is currently analog transmission, but it will shift to digital transmission in the future. In that case, the supplied information (television signal) is not only uniform information such as the current analog NTSC signal, but also , Video and audio quality (information compression ratio)
The transmission rate of data and data can be set to some extent freely according to the viewer's request, and the transmission information itself can widely transmit not only television signals but also other digital information. I think that the.

[0004] Technical information on CATV can be found, for example, in the Journal of the Institute of Television Engineers of Japan, Vol. 47, no. 8 19
93 "Special Edition: Technical Trends in Cable TV" P104
8 to P1087.

Also, as a compression method by digital signal processing of current video (moving picture) information, MPEG (Moving Picture I / O) using motion compensation and DCT (Discrete Cosine Transform) is used.
mageCoding Expert Group) method has been developed, and significant compression is becoming possible. In general, the compression ratio and quality in video information and the like conflict with each other, but they are used depending on the purpose and purpose. For example, in the case of the current television (NTSC) signal, the quality after compression is reduced to the quality equivalent to the VTR recording level. It has been reported that transmission is possible at about 1.5 Mbps, at a television reception level quality of 4 to 5 Mbps, and at a high vision signal reception level quality at about 20 Mbps.

Hereinafter, NTSC of about 1.5 Mbps transmission will be described.
The signal is called a high-compression NTSC signal, and the NTSC signal of about 4 to 5 Mbps transmission is called a low-compression NTSC signal.
A Hi-Vision signal of about Mbps transmission is called a compressed Hi-Vision signal. Regarding the compression technique of video information, for example, Journal of the Institute of Television Engineers of Japan, Vol. 47, no. 61
993 “Special Edition: Digital Recording Technology and Its Applications, 1
-2: Trends in digital video technology and digital recording technology ”, P801 to P806, and the same magazine, Vol. 47, no.
10 1993 “Trends in Digital Video Transmission Technology” P
1269 to P1276.

[0007] Information with different transmission rates as described above is
For example, when transmission is performed using the same transmission path such as CATV, one channel of a compressed Hi-Vision signal is used for 4 to 5 channels of a low-compression NTSC signal and one channel of a high-compression NTSC signal.
Three channels can be transmitted.

On the other hand, a VTR for recording and reproducing such digital information has not been commercialized at the present time. However, for example, Nikkei Electronics, 1993.7.39 (No. 58)
6) As described on page 66, the transmission rate in recording / reproducing is 25 Mbp in a single head configuration even at a consumer product level due to an increase in the relative speed between the magnetic head and the tape.
s, 50Mb in multi-head (2 channel) configuration
A digital VTR having a recording / reproducing transmission rate of about ps has been proposed.

Therefore, if a digital VTR having a recording / reproducing transmission rate of about 25 Mbps is used,
Starting with the compressed HDTV signal (for one channel) which is the maximum transmission rate of each compressed digital television signal including redundant data, etc.
Signals can be recorded for 4 to 5 channels, and 13 channels for high compression NTSC signals. In addition,
The above qualities and data transmission rates represent one specific example.

When video information or audio information is handled as a digital signal, the digital information must be transmitted or recorded without distinction from video, audio, programs and data handled by a computer, and any other digital information. Can be. That is, the transmission and recording of digital information can be processed irrespective of the type of information to be processed, and in the future CA
Using a transmission path such as a TV, it is possible to supply not only television signals but also all digital information such as programs handled by a computer and their data.

However, in the above technique, there is no problem with regard to transmission or recording of a compressed Hi-Vision signal, which is the highest transmission rate, but a low-compression NTSC signal or a high-compression NTSC signal transmitted over a plurality of channels at the same time is recorded. In this case, the transmission path and VTR (recording medium) cannot be used effectively and efficiently unless the viewer (VTR user) wants to record all the channels simultaneously.

That is, when it is desired to record only one desired channel of a low-compression NTSC signal or a high-compression NTSC signal, unnecessary and unnecessary channel information is also transmitted and recorded together.
The utilization efficiency of the (recording medium) is about 8 to 20% (in the case of the above transmission rate). This means that even if only the necessary channels are transmitted and recorded, the transmission path and the VTR (recording medium) side have sufficient capacity, and this cannot be utilized. It is about 20%. In addition, the efficiency of the transmission and recording of programs handled by computer equipment having a low transmission rate and their data are further reduced.

In order to solve these problems, it is possible to make use of the characteristics of the digital signal and transmit the data at the same data transmission rate by means such as time axis compression regardless of the type of information. Conceivable. This is to increase the transmission rate of information with a low transmission rate by compressing the time axis, thereby shortening the transmission time. For example, when transmitting the above-described low-compression NTSC signal (4 to 5 Mbps), the time axis is compressed 4 to 5 times, and the transmission rate is set to 20 Mbps.
s, for example, to convert a one-hour program into 1/4 to 1/5
It is transmitted and recorded in 5 to 12 minutes.

[0014]

However, in the information transmission by the same transmission rate conversion based on the time axis compression described above, the viewer (information receiver) side performs a time axis expansion process opposite to the time axis compression described above. Required. If this time axis expansion processing is performed using a buffer memory (a memory for temporarily storing data) or the like, an enormous memory capacity is required. For example, if the transmission rate is 4Mbps, 60
When a minute program is compressed on the 1/5 time axis and transmitted at a transmission rate of 20 Mbps for 12 minutes, a data amount (11.52) corresponding to a transmission rate of 4 Mbps at a minimum of 48 minutes.
Gbit) buffer memory is required, resulting in a large-scale and expensive system.

Further, it is necessary to increase the buffer memory as the program becomes longer. Also, the recording of information of the same transmission rate by the above-mentioned time axis compression on the VTR on the viewer side can be easily realized by using the above digital VTR. Requires a huge buffer memory.

Accordingly, an object of the present invention is to provide a helical scanning type capable of extending and reproducing a time axis to an original state without recording and reproducing a large amount of buffer memory when recording and reproducing information having different time axis compression ratios. To provide a recording / reproducing device.

[0017]

[0018]

In order to achieve the above object, according to the present invention, in a helical scanning type recording / reproducing apparatus, a time axis compression ratio of a digital information signal supplied via a transmission line during recording is determined. Identification signal generating means for generating an identification signal corresponding to the identification information; recording means for multiplex-recording the identification signal generated by the identification signal generation means together with the digital information signal on a recording medium; Reproducing means for reproducing an identification signal corresponding to the axial compression ratio together with the digital information signal.

Identification signal detection means for detecting the identification signal from the reproduction signal, recording medium traveling speed switching means for switching the recording medium traveling speed during reproduction according to the identification signal detected by the identification signal detection means, Memory means for temporarily storing the digital information signal thus obtained,
Memory control means for reading out the reproduced digital information signal stored in the memory means at a predetermined transmission rate.

[0020]

[0021]

[0022]

First, a discrimination signal generating means for discriminating the time axis, recording / reproducing means for discriminating signal, and discrimination signal detecting means determine the time axis expansion rate of the reproduced digital information, and convert the digital information signal to the original time axis during reproduction. Get information to return to. The recording medium (tape) running speed switching means sets the tape speed at the time of reproduction in accordance with the identification signal to a tape speed equal to the time axis compression ratio.
The speed is switched to the deceleration speed.
/ 4, the tape speed at the time of reproduction is reduced to １ ／ of that at the time of recording, and the reproduction digital information per unit time is reduced to ４.
To decrease. The memory means and the memory control means extend the time axis of the reproduced digital information, extend the time axis compressed digital information signal to the original time axis, and output it as a continuous signal.

[0023]

[0024]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, before a detailed description of the helical scanning type recording / reproducing apparatus of the present invention, a use environment of the present apparatus will be briefly described with reference to FIGS.

FIG. 2 is an explanatory diagram showing a use environment of a helical scanning type recording / reproducing apparatus to which the present invention is applied. FIG.
In the figure, a broken line part 31 indicates a transmitting station for supplying a digital information signal, a transmission line 32 for a digital information signal, and a broken line part 33 a viewer (user) device having the helical scanning type recording / reproducing apparatus. Is shown.

The transmitting station 31 is, for example, a digital VTR
34, a disk device 35, or a semiconductor recording / reproducing device 36 using a large-capacity memory, the time axis of the digital information signal is compressed, and the transmission rate is the same regardless of the type of information. 37. In addition,
The digital information signal is subjected to error detection and detection in order to prevent adverse effects due to the occurrence of code errors (errors) in the transmission process.
Redundant data such as a correction code, an identification signal such as a synchronizing signal and a type of information, and information on a time axis compression ratio are added to the modulation signal and supplied to the modulation circuit 37.

The modulation circuit 37 converts the digital information signal into an efficient signal form suitable for the characteristics of the transmission path 32 at the next stage, for example, multi-level QAM and outputs it. The digital information signal supplied via the transmission path 32 is expanded in the original time axis by the helical scanning type recording / reproducing device 38, and when the transmission information is a video and audio signal, it is further converted into an analog signal and converted into a television signal. The data is output to the monitor 39 and can be viewed.

On the other hand, when the transmission information signal is a program or data used for a computer device or the like, the transmission information signal is reproduced at a transmission rate suitable for the external device by a control signal supplied from the outside, and is transmitted to the computer. Is supplied to the data equipment 40.
Whether the transmitted digital information signal is a video signal or an audio signal, or a signal such as a program and data is determined by multiplexing an identification signal indicating the signal and detecting and identifying the signal. And can be easily determined.

FIG. 3 is an explanatory diagram showing the relationship between the transmission rate of a plurality of types of television signals and the time base compression ratio in the present embodiment. In this embodiment, the following three types of TV signal types will be described as examples.

In FIG. 3, (1) is a compressed Hi-Vision signal, and the transmission rate is 18 Mbps.
(2) is a low compression NTSC signal and the transmission rate is 4.5.
Mbps. (3) is a low-compression NTSC signal that is time-axis-compressed by a quarter, and the transmission rate is 18 Mbps. (4) is a high-compression NTSC signal and the transmission rate is 1.5 Mbps. (5) is a high-compression NTSC signal whose time base has been compressed by a factor of 12, and the transmission rate is 18M.
bps. In this embodiment, the transmission possible rate of the transmission line is considered to be about 18 Mbps except for the redundant data, so the time axis compression ratio is determined so that the transmission rate becomes 18 Mbps.

FIG. 1 is a block diagram showing the configuration of a helical scanning type recording / reproducing apparatus (an embodiment of the present invention) to which the present invention is applied. In FIG. 1, 1 is a magnetic tape, 2 is a drum (including a drum motor), 3A and 3B are magnetic heads, 4 is a capstan, and 5 is a capstan motor.
6 to 12 are input or output terminals, 13 is a channel selector (tuner), 14 is a demodulation circuit, 15 is a PCM decoder, and 16 is a digital signal processor (hereinafter referred to as DSP). .

In addition, 17 is a modulation circuit, 18 is a recording amplifier, 19 is a system controller, and 20 is a drum server.
Circuit, 21 is a capstan servo circuit, 22 is a reproduction amplifier, 23 is a demodulation circuit, 24 is a tracking circuit, 25
Is a DSP, 26 is a PCM decoder, 27 is a memory control circuit, 28 is a memory, 29 is a decoder (information decompression circuit),
Reference numeral 30 denotes a DA converter. Hereinafter, operations during recording and reproduction will be described along the flow of signals.

In FIG. 1, an input information signal supplied via an input terminal 6 is supplied to a channel selector 13. The channel selector 13 is connected to the system controller.
The information signal of the desired channel is selected according to the channel designation signal CH supplied from the controller 19 and supplied to the demodulation circuit 14. The channel designation signal CH is supplied to the input terminal 7
Is set by a user command signal supplied via the.

The demodulation circuit 14 demodulates the input information signal modulated in a signal form suitable for the transmission line 32, converts the demodulated input information signal into a digital signal, and supplies the digital signal to the PCM decoder 15. P
The CM decoder 15 performs error detection and correction of the input digital information signal, supplies a digital information signal to the DSP 16 at the next stage, detects an identification signal, and supplies the identification signal to the system controller 19. Further, the synchronizing signal is separated and supplied to the drum servo circuit 20.

System control supplied with the identification signal
The laser 19 selects data necessary for reproduction of, for example, information on the time axis compression ratio or information indicating the type of the recording information signal from the identification signals, supplies the data to the DSP 16, and outputs the data via the output terminal 8. Although not shown, it is supplied to a display system to display the information of the identification signal to the user.

The DSP 16 is connected to the digital information signal supplied from the PCM decoder 15 and the system controller 1.
9 is converted into a signal form suitable for magnetic recording and reproduction. That is, in order to cope with a code error in magnetic recording / reproducing, data is blocked and address data is added, and a strong error detection / correction code such as an interleave and a read-solomon code is added. Is applied. The recording information signal on which the signal processing has been performed by the DSP 16 is supplied to the modulation circuit 17.

The modulation circuit 17 modulates the recording information signal into a digital signal suitable for magnetic recording, such as 8-10 conversion or 8-12 conversion, and supplies the digital signal to the recording amplifier 18. The recording amplifier 18 amplifies the recording digital signal to a level suitable for magnetic recording and records it on a magnetic tape via the magnetic heads 3A and 3B.

In this embodiment, the case of 180-degree opposed two-head helical scanning is taken as an example, and the rotational frequency of the drum is 3 times the frame frequency of the television signal in order to secure a recording transmission rate of about 25 Mbps. Times (about 5400r
pm). Therefore, the number of tracks formed in the field period of the television signal is three. FIG. 4 is a schematic diagram of a track pattern when the digital signal recorded as described above is a plurality of types of television signals.

In FIG. 4, (1) shows the case of a compressed HDTV signal, (2) shows the case of a low-compression NTSC signal,
(3) shows the case of a high compression NTSC signal, respectively. In each case, 3 tracks are recorded, so 1
This corresponds to recording of a field cycle period.

In FIG. 4, numerals 1 to 12 given on the tracks represent the numbers of the recorded fields. In the case of the compressed Hi-Vision signal of (1), one field information is recorded in one field period (three tracks) because time axis compression is not performed.
In the case of the low-compression NTSC signal of (2), since the time-base compression ratio is 1/4, four fields of information are recorded during the same period,
In the case of the high-compression NTSC signal of (3), since the time base compression ratio is 1/12, 12 fields of information are recorded during the same period.

In FIG. 4, the track area per field is schematically divided, and the input information signal is a signal such as a variable length code.
If the amount of information for each field is different, the recording area for each field information is naturally different.

Here, the servo of the drum and the capstan at the time of recording will be described. The control of the drum and the capstan is performed by the drum servo circuit 20 and the capstan servo circuit 21 according to the drum and capstan command signals DC and CC supplied from the system controller 19.

FIG. 5 is a block diagram showing the internal configuration of the drum servo circuit 20 and the capstan servo circuit 21. In FIG. 5, a broken line portion 20 is a drum servo circuit, and a broken line portion 21 is a capstan servo circuit. 41 to 47 are input terminals, 48 and 49 are output terminals, 5
Reference numerals 0 and 59 are speed detection circuits, 51 and 60 are speed target setting circuits, 52, 55 and 61 are subtraction circuits, 53 is a phase detection circuit, 54 is a phase target setting circuit, 56 and 64 are addition and characteristic compensation circuits, 57 , 65 are DA converters, 58 and 66 are motor driver amplifiers (hereinafter referred to as MDA),
62 is an integration circuit, and 63 is a switch.

First, the drum servo will be described. In FIG. 5, the DFG supplied via the input terminal 42
(Drum Frequency Generate
r) The signal is supplied to the speed detection circuit 50. Although not shown, the DFG signal generating mechanism is a frequency signal generated in proportion to the rotation frequency of the drum 2. Speed detection circuit 5
0 detects the rotation speed of the drum 2 by measuring the period of the DFG signal, and supplies the speed detection information to the subtraction circuit 52.

From the system controller 19 to the input terminal 4
1 is supplied to a speed target setting circuit 51 and a phase target setting circuit 54.
The speed target setting circuit 51 generates a rotation speed target of the drum 2 which is three times the frame frequency in accordance with the drum command signal DC, and supplies the speed target information to the subtraction circuit 52. The subtraction circuit 52 performs a subtraction between the speed detection information and the speed target information, and supplies the speed error information, which is a difference between the two, to an addition & characteristic compensation circuit 56.

On the other hand, D supplied through the input terminal 43
The PG (Dram Phase Generator) signal is supplied to the phase detection circuit 53. Although not shown, the DPG signal is synchronized with the rotation of the drum 2 and the magnetic head 3
This is a phase signal having a predetermined phase relationship with the rotation phase of A or 3B. The phase detection circuit 53 detects the rotation phase of the drum 2 by detecting the phase of the DPG signal, and supplies the phase detection information to the subtraction circuit 55.

The phase target setting circuit 54 uses the PCM
The phase target information is generated from the synchronizing signal of the input information signal supplied from the decoder 15 through the input terminal 44, and the phase target information is supplied to the subtraction circuit 55. Subtraction circuit 55
Performs the subtraction between the above-mentioned phase detection information and the phase target information, and supplies the difference, that is, phase error information, to the addition & characteristic compensation circuit 56. The adding & characteristic compensating circuit 56 adds the speed error information and the phase error information, and performs a characteristic compensating filter processing such as phase delay compensation so as to obtain a desired servo characteristic. To supply.

The DA converter 57 converts the drum control signal supplied from the addition & characteristic compensation circuit 56 into an analog signal and supplies the analog signal to the MDA 58. The MDA 58 amplifies the power of the drum control signal and outputs the amplified signal to the output terminal 4 as a drum drive signal.
The drum 2 is supplied to the drum 2 via the control unit 8 to rotate the drum 2 at a predetermined speed at a predetermined phase. The above-mentioned phase target information is generated by using the synchronizing signal of the input information signal. However, this is achieved by controlling the rotation of the drum 2 in accordance with the transmission rate of the input information signal, thereby passing the input information signal. It is intended to be able to record without lack.

Next, the capstan servo will be described. In FIG. 5, C supplied through an input terminal 46
FG (Capsutan Frequency Gen)
erater) signal is supplied to the speed detection circuit 59.
Although a CFG signal generating mechanism is not shown, it is a frequency signal generated in proportion to the rotation frequency of the capstan 4 like the DFG signal.

The speed detection circuit 59 detects the rotation speed of the capstan 4 by measuring the period of the CFG signal,
The speed detection information is supplied to the subtraction circuit 61. The capstan command signal CC supplied from the system controller 19 via the input terminal 45 is supplied to the speed target setting circuit 60. The speed target setting circuit 60 generates a rotation speed target of the capstan 4 according to the capstan command signal CC, and supplies the speed target information to the subtraction circuit 61.

The subtraction circuit 61 performs a subtraction between the speed detection information and the speed target information, and obtains a speed error which is a difference between the two.
The information is supplied to the addition & characteristic compensation circuit 64 and the integration circuit 62. The integration circuit 62 generates speed error integration information by sequentially accumulating the speed error information supplied from the subtraction circuit 61, and outputs the speed error integration information to the switch 63.
To supply.

The switch 63 is closed on the A input terminal side during recording, and supplies the speed error integration information output from the integration circuit 62 to the addition & characteristic compensation circuit 64. The addition & characteristic compensation circuit 64 adds the speed error information and the speed error integration information, and performs a characteristic compensation filter processing such as a phase delay compensation so as to obtain a desired servo characteristic. 65.

The DA converter 65 converts the capstan control signal supplied from the addition & characteristic compensation circuit 64 into an analog signal and supplies the analog signal to the MDA 66. The MDA 66 amplifies the power of the capstan control signal and supplies it as a capstan drive signal to the capstan motor 5 via the output terminal 49, rotates the capstan 2 at a predetermined speed, and drives the magnetic tape 1 at a predetermined speed. Run with. The integrating circuit 62 has an integral control system in addition to the speed system (proportional control system) so that the steady speed deviation becomes zero.

In the recording operation described above, a pilot signal is added by the recording amplifier 18 as a signal necessary for tracking control at the time of reproduction, and is recorded in a frequency multiplexed manner with the recording information signal. The tracking control based on the pilot signal is used in, for example, 8 mm video, and is well known, so a detailed description thereof will be omitted. Since the recording signal of the above pilot signal is a digital signal, a digital sum value (DSV) for frequency-multiplexing the pilot signal component in the modulation process is used.
The signal may be generated by the modulation circuit 17 according to the method e).

The operation of the present apparatus at the time of recording has been described above. Next, the operation during reproduction, which is an important part of the present invention, will be described. At the time of reproduction, it is necessary to switch the tape running speed in accordance with the recorded information, which detects an identification signal multiplexed on the recorded information signal and reproduces the reproduction tape in accordance with the identification signal. Determine the speed.
Therefore, at the time of reproduction, information recorded on the portion wound around the drum at that time is reproduced in a so-called still state and the identification signal is detected prior to the tape running. First, detection of the identification signal will be described.

In FIG. 1, the magnetic head 3A or 3A
The reproduction signal reproduced from the magnetic tape 1 at B is supplied to a demodulation circuit 23 and a tracking control circuit 24 after being sufficiently amplified by a reproduction amplifier 22. The demodulation circuit 23 equalizes the waveform of the supplied reproduction information signal, extracts a clock component, strobes the reproduction data using this clock, and converts it into a logic signal. Then, a demodulation process reverse to that at the time of recording is performed, and a demodulated reproduced digital signal is supplied to the DSP 25.

The DSP 25 performs error detection and correction of the reproduced digital signal, performs deinterleaving on the basis of the address information, returns the data to the original data permutation, and supplies it to the PCM decoder 26. The PCM decoder 26 detects the identification signal from the reproduced digital signal, and supplies the identification signal information to the system controller 19 and supplies the reproduced digital signal to the memory 28. System controller 19
Identifies the type of the reproduced digital information signal from the identification signal information. If the reproduction information signal is a television signal, the reproduction tape speed and the time axis expansion rate of the reproduction information signal are determined according to the time axis compression rate.

First, the case where the reproduction information signal is a compressed high vision signal will be described. The compressed HD signal is
Since time axis compression is not performed, the system controller 19 generates a capstan command signal CC so that the playback tape speed is set to the same speed as during recording.

Thus, in the capstan servo circuit 21 shown in FIG. 5, the speed target setting circuit 60 generates the same speed target information as at the time of recording, and supplies the same to the subtraction circuit 61. When the tape traveling speed is made equal between recording and reproduction, tracking control is necessary in addition to the speed control. In this tracking control, by closing the switch 63 in FIG. 5 to the B input terminal side, the tracking error information supplied from the tracking control circuit 24 shown in FIG. It is done by returning.

The tracking control circuit 24 extracts the pilot signals from the tracks adjacent to the track to be scanned by the magnetic head from the reproduction signal output from the reproduction amplifier 22, and compares the levels of the two pilot signals. Generates tracking error information. The above-mentioned speed error information and tracking error information are added by an addition & characteristic compensation circuit 64, and characteristic compensation filter processing such as phase delay compensation is performed in the same manner as in recording, and a DA converter 65,
It is supplied to the capstan motor 5 via the MDA 66. As a result, the magnetic tape 1 runs in the on-tracking state at the same constant speed during recording.

In the control of the drum 2, since the synchronizing signal of the input information signal is not supplied during reproduction, the phase target setting circuit 54 shown in FIG. Using a stable clock, a phase reference signal having a frequency three times the frame frequency of the television signal is generated, and a phase target signal is generated based on the phase reference signal and supplied to the subtraction circuit 55. When reproducing the compressed Hi-Vision signal as described above, the tape running speed and the drum rotational speed are set in the same manner as during recording.

On the other hand, the system controller 19 supplies the memory control circuit 27 with the time base expansion rate setting signal MC. The memory control circuit 27 has a time-axis expansion rate setting signal MC.
When the compressed high-definition signal is reproduced according to the following formula, the transmission rate of the reproduction digital information written in the memory 28 and the transmission rate of the reproduction digital information read from the memory 28 are made equal so that the time base expansion is not performed.
Control. The reproduced digital information read from the memory 28 is supplied to a decoder 29.

The decoder 29 is connected to the system controller 1
9 decodes the compressed HDTV signal into the original HDTV signal format in accordance with the identification signal of the compressed information supplied from 9, and supplies the reproduced digital HDTV signal to the DA converter 30. The DA converter 30 converts the reproduced digital Hi-Vision signal and the audio signal attached thereto into an analog signal, and outputs the video signal and the audio signal via the output terminals 10 and 11, respectively.

Next, a case where the reproduced information signal is a low-compression NTSC signal will be described. Since the low-compression NTSC signal has a time-axis compression ratio of 1/4, the system controller 19 generates a capstan command signal CC so that the reproduction tape speed is set to 1/4 the speed at the time of recording.

As a result, in the capstan servo circuit 21, the speed target setting circuit 60 generates speed target information that is １ ／ of that at the time of recording and supplies it to the subtraction circuit 61. If the tape running speed differs between recording and reproduction, the magnetic head during reproduction crosses the recording track because the recording track pattern and the inclination of the magnetic head scanning locus during reproduction are different. Therefore, in the present embodiment, when the reproduction information signal is compressed on the time axis, that is, when the tape traveling speed during reproduction is different from that during recording, the tracking control by the pilot signal is not performed and the integrated signal of the velocity error is performed in the same manner as during recording The tape speed control is performed by using.

Therefore, in reproducing the low-compression NTSC signal, the switch 63 shown in FIG. 5 is closed to the A input terminal side. Here, the tracking state in the case where the tape traveling speed during reproduction is different from that during recording will be described.

FIG. 6 is an explanatory diagram showing an example of a magnetic head scanning trajectory at the time of reproduction with respect to a recording track pattern when the tape traveling speed at the time of reproduction is 記録 of that at the time of recording, by a track pattern coordinate method.

In FIG. 6, an area (one cell) marked with a, b, c,..., I is one track. There are four steps from the top to the bottom, one of which is the longitudinal direction of the tape. If the tape running speed during playback is the same as during recording,
In FIG. 6, the magnetic head scans a, b, c, and d and the recording track pattern from bottom to top. From point P1 to point P2, then P3, P
4 and the magnetic head scan.

Therefore, in the case of azimuth recording, a reproduced signal is obtained in a portion where a vertical line or a horizontal line is given in the figure, and a reproduced envelope signal shown on the left side of the figure is obtained. In other words, when going from point P1 to point P2, it is considered that data of track d is taken. However, after data of track d is taken at the first stage, data of track d is taken at the second stage because of the inverted azimuth. Although a part of the track e and a part of the track c can be obtained, this is not desired data (data of the track d) and is discarded. Similarly, the data of the track d is obtained in the third stage, and the data of the track d is not obtained in the fourth stage because of the inverted azimuth. A part of the track e is obtained but discarded. As a result, a reproduction envelope signal shown on the left of FIG. 6 is obtained.

Here, it is assumed that a signal of track d is detected by scanning from point P1 to point P2, a signal of track e is detected by scanning from point P2 to point P3, and a signal of track f is detected. Thus, information for one track can be detected by the time required for scanning four tracks, and as a result, the time axis is extended four times in units of information corresponding to one track.

However, in the above case, the magnetic head at the time of reproduction scans the recording track diagonally, which partially lowers the reproduction envelope signal level. When the width of the magnetic head is equal to the width of the recording track, the rate of decrease in the level of the reproduction envelope signal is equal to the ratio of the reproduction speed to the tape traveling speed during recording. Therefore, in the case of reproducing a low-compression NTSC signal in which the tape traveling speed during reproduction is 1/4, the reduction rate of the reproduction envelope signal level is 1/4, that is, 25%.

The rate of decrease in the level of the reproduction envelope signal depends on the tape running speed during reproduction, but does not depend on the tracking state (the state in which the magnetic head scanning trajectory has moved in parallel in FIG. 6). FIG. 7 shows the relationship between the tracking state and the level of the reproduction envelope signal when the tape traveling speed during reproduction is 1/4 of that during recording.

In FIG. 7, the reference state (1) represents the reproduction envelope signal level when the magnetic head in FIG. 6 scans from point P1 to point P2 (that is, the reproduction envelope signal shown on the left of FIG. 6, ie, (The first and third stage envelope signals are displayed in an overlapping manner.) (2) shows the case where the magnetic head trajectory is moved parallel to the following track with respect to the state of (1). Represents
(3) shows a case where the magnetic head trajectory has moved in parallel to the preceding track with respect to the state of (1).

In any state, the maximum reduction rate of the reproduction envelope signal level is 25%, which indicates that the level does not depend on the tracking state. The rate of decrease in the reproduction envelope signal level can be halved, for example, in the case of reproduction with a double azimuth type composite head. Can be reduced.

Specifically, if the width of the magnetic head is increased by 20% compared to the track width, the decrease rate is reduced by half to 10%.
It can be improved and the reduction rate can be made 15%. Even when the reproduced information signal is a low-compression NTSC signal, the control of the drum 2 is performed at three times the frame frequency as in the case of reproducing the compressed high-definition signal because the synchronizing signal of the input information signal is not supplied during the reproduction. And a phase target signal is generated based on the phase reference signal, and the drum rotation speed is set in the same manner as during recording.

In FIG. 1, the system controller 19 supplies a time base expansion rate setting signal MC to the memory control circuit 27. The memory control circuit 27 has a time-axis expansion rate setting signal MC.
When the low-compression NTSC signal is reproduced according to the above, the memory 28 is controlled so that the time axis is expanded four times. As can be seen from FIGS. 6 and 7, since the tape traveling speed during reproduction is reduced to 1/4, a scanning period of 3 tracks or 5 tracks is required to detect reproduction information for one track. In other words, a scanning period of eight tracks is required to detect reproduction information for two tracks. Therefore, the memory 28 has a capacity to store reproduction information for two tracks, and performs quadruple time axis expansion by reading reproduction information for two tracks over an eight-track scanning period.

The reproduced digital information read from the memory 28 is supplied to a decoder 29. The decoder 29
The low-compression NTSC signal is decoded into the original NTSC signal form in accordance with the compression information identification signal supplied from the system controller 19, and the reproduced digital NTSC signal is supplied to the DA converter 30. DA converter 3
Numeral 0 converts the reproduced digital NTSC signal and the audio signal attached thereto to an analog signal, and outputs the video signal and the audio signal via the output terminals 10 and 11, respectively.

Next, a case where the reproduction information signal is a high compression NTSC signal will be described. The operation at the time of reproducing the high compression NTSC signal is basically the same as the operation of reproducing the low compression NTSC signal. The difference is that the time axis compression ratio is changed from 1/4 to 1/12. Therefore, at the time of reproducing a high-compression NTSC signal, the reproducing tape running speed is set to 1/12 of the recording speed, and the control of the memory 28 for extending the time axis is performed by controlling the reproduction information of one track to 12 tracks. Reading is performed over a scanning period.

The above is the operation when the television signal is recorded. Hereinafter, a case where the recorded digital information is a program or data used by an external digital device such as a computer, that is, a case where the present apparatus is used as a data recorder will be described for reference .

When this apparatus is used as a data recorder, for example, as shown in FIG. 2, the transmission rate of the reproduced signal is controlled by an external digital device 40 such as a computer connected to the outside.
It is necessary to switch according to the request of. Therefore, in the present reference example , the system controller 19 shown in FIG. 1 is provided with an input terminal 9 for a transmission rate setting signal supplied from an external digital device.

When the transmission rate is determined by the transmission rate setting signal supplied from the external digital device, the system controller 19 determines the time axis expansion during reproduction from the recording transmission rate of digital information during recording and the transmission rate during reproduction. The tape running speed at the time of reproduction is determined according to the time axis expansion rate, and a capstan command signal CC is supplied to a capstan servo circuit. Further, a memory control setting signal MC is supplied to the memory control circuit 27 to switch the transmission rate in the memory 28, the reproduced digital signal is converted into a transmission rate required by the external digital device, and output via the output terminal 12.

As described above, according to this embodiment, the transmission rates supplied via the same transmission line are substantially equal,
A large-scale buffer memory can be stored by recording multiple types of TV signals with different time-axis compression rates at the same transmission rate when recording, and playing back at the tape running speed according to the time-axis compression rate of the recorded information during playback. It is possible to extend the time axis to the original state and play it back without any need.

Further, the recorded information is not limited to the television signal,
In the case of a program used in a digital device such as a computer and digital information such as data handled in the program, data required by an externally connected digital device.
The tape running speed can be switched so as to achieve the data transmission rate, the time axis can be extended, and the reproduced data can be output.
That was also mentioned for reference.

In this embodiment, three types of television signals are used, and the transmission rate of the transmission path is 18 Mbps.
However, the relationship between the type, the transmission rate, and the time axis compression ratio is, of course, not limited to the above.

In the present embodiment, a method using a pilot signal for tracking control is adopted. However, the tracking control is performed by a CTL using a control signal recorded in the longitudinal direction of the tape as used in VHS video, for example. There is no problem with the system.

[0086]

As described above, according to the present invention, the transmission rates supplied through the same transmission line are substantially equal,
In recording and playback of multiple types of TV signals with different time axis compression ratios, by reproducing the recorded information at the tape running speed according to the time axis compression ratio of the recorded information, the time axis can be restored without requiring a large-scale buffer memory. There is an advantage that it is possible to expand and reproduce in the state of FIG.

[0087]

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a helical scanning type recording / reproducing apparatus as one embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a use environment of a helical scanning type recording / reproducing apparatus according to the present invention.

FIG. 3 is an explanatory diagram showing an example of a transmission rate and a time axis compression ratio of a television signal to be recorded and reproduced.

FIG. 4 is an explanatory diagram showing an example of a track pattern when a plurality of television signals having different time axis compression ratios are helically recorded.

FIG. 5 is a block diagram showing a configuration of a servo circuit of a drum and a capstan.

FIG. 6 is a pattern diagram showing a magnetic head scanning locus by a track pattern coordinate method when a recording track pattern and a reproducing tape traveling speed are set to １ ／ of a recording speed.

FIG. 7 is a characteristic diagram showing the level of a playback envelope signal when the playback tape speed is reduced to 1/4 of the recording speed.

[Description of Signs] 13: Channel selector, 14, 23 ... Demodulation circuit, 1
5, 26 ... PCM decoder, 16, 25 ... digital signal processor (DS,), 17, 37 ... modulation circuit,
19: System controller, 20: Drum servo circuit, 21: Capstan servo circuit, 24: Tracking control circuit, 27: Memory control circuit, 28: Memory, 2
9 Information decompression decoder, 30, 57, 65 DA converter, 50, 59 Speed detection circuit, 51, 60 Speed target setting circuit, 52, 55, 61 Subtraction circuit, 53 Phase detection circuit, 54 Phase Target setting circuit, 56, 64: Addition and characteristic compensation circuit, 58, 66: Motor driver amplifier

Continued on the front page (72) Inventor Hiroya Abe 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Hitachi Media Media Research Laboratories Co., Ltd. (72) Inventor: Iwao Ayuzawa 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Pref. Hitachi Media Video Research Laboratory, Inc. (56) References JP-A-6-349014 (JP, A) ( 58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 5/09

Claims (3)

(57) [Claims] 1. A helical scanning type recording / reproducing apparatus for recording / reproducing a plurality of types of digital information signals having different time-axis compression ratios and substantially equal transmission rates supplied through a transmission path. An identification signal generating means for knowing the time axis compression ratio of the digital information signal and generating an identification signal corresponding to the time axis compression ratio;
Recording means for multiplexing the identification signal generated by the identification signal generation means and recording the identification signal on a recording medium; and an identification signal corresponding to the time axis compression ratio of the recorded digital information signal, and multiplexing the identification signal together with the digital information signal. Reproducing means for reproducing the identification signal together with the digital information signal from a recording medium which has been recorded and recorded; identification signal detecting means for detecting the identification signal from a reproduction signal by the reproducing means; and identification signal detecting means A helical scanning type recording / reproducing apparatus, comprising: a recording medium traveling speed switching means for switching a recording medium traveling speed at the time of reproduction in accordance with a time axis compression ratio represented by an identification signal detected by the above. 2. A helical scanning type recording / reproducing apparatus according to claim 1, wherein said identification signal generating means is multiplexed with a digital information signal supplied via said transmission path and supplied therewith. A helical scanning type recording / reproducing apparatus which uses information to generate an identification signal corresponding to the information. 3. The helical scanning type recording / reproducing apparatus according to claim 1, wherein said recording medium traveling speed switching means has a time axis compression ratio represented by an identification signal detected by said identification signal detection means of 1 / N. (Where N is a positive real number), the helical scanning type recording / reproducing apparatus switches the recording medium traveling speed during reproduction to 1 / N of the recording medium traveling speed during recording.