JPH0683475B2 - Video tape recorder - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a helical scan type video tape recorder, and more particularly to a video tape recorder suitable for reproducing a time-axis compressed PCM audio signal.

[Background of the Invention]

As an example of the helical scan type video tape recorder, there is a home video tape recorder called 8 mm video standard whose tape pattern is shown in FIG.

In FIG. 12, 1 is a video tape, 2 is a video track on which a video signal is recorded, 3 is a first option track, 4 is a second option track, 5 is an arrow indicating the direction in which the rotary head traces, 6 Is an arrow indicating the running direction of the videotape, 7 is an audio signal converted into a PCM signal,
Furthermore, it is a track on which a signal whose time axis is compressed is recorded in about 1/6.

In FIG. 12, θ ₁ , θ ₂ , θ ₃ , and θ ₄ respectively indicate the winding angles of the video tape wound around the rotary cylinder, and θ ₁
≈ θ ₄ ≈ 5 °, θ ₂ = 10 °, θ ₃ ≈ 30 °. Here, θ ₂ corresponds to the period during which the video signal is recorded, and θ ₃
Corresponds to the period during which the audio signal is recorded, and θ ₁ , θ
₄ is a margin for ensuring compatibility (hereinafter, the tape pattern recording method shown in FIG. 12 is referred to as a video signal recording mode). Therefore, when used for recording only an audio signal, the margin on the video tape is The area used for recording is
Only the part indicated by 7 in Fig. 12 was poor, and the video tape utilization efficiency was poor.

As a method for improving this, as shown in FIG. 13, the video track 2 is divided into five areas B to F, and each area is divided into the 12th area.
Similar to FIG. 7 (corresponding to area A in FIG. 13), there is a system for recording a time-axis-compressed PCM signal (hereinafter, the tape pattern recording system shown in FIG. 13 is referred to as a multi-PCM recording mode). (JP-A-58-222402) In this system, the audio signal can be recorded 6 times as compared with the system in FIG.
With the above-described multi-PCM recording mode, the usage of the video tape recorder can be expanded to the audio area.

However, since the above video tape recorder operates based on the periodic signal obtained from the video signal, NT
There are two systems, SC and CCIR, and there is no compatibility between the two systems as the standard is 30Hz for NTSC system and 25Hz for CCIR system. As a result, unlike television systems, not only can we not fully utilize the features of audio systems that monitor systems are common throughout the world, but also many disadvantages such as the need for soft tapes that support the two systems. There was a problem that it would end up.

[Object of the Invention]

An object of the present invention is to determine in which method a reproduction signal from a magnetic tape is recorded in a helical scan type video tape recorder capable of recording and reproducing video signals of different TV methods such as NTSC method and CCIR method. A video tape recorder for controlling the reproducing operation is obtained based on the result of this discrimination.

[Outline of Invention]

In order to achieve the above object, the present invention provides a video tape recorder using two methods, an identification method of a tape recording system using a reproduction frequency of a pilot signal for tracking servo and an identification method of a tape recording system using a PCM signal. It automatically switches the playback system.

Example of Invention

The video tape recorder of the present invention will be described below with reference to the embodiments shown in the drawings. FIG. 1 shows an example in which the present invention is applied to a reproducing system of a video tape recorder (VTR) of 8 mm video standard.

The VTR in Fig. 1 can be played back on tape recorded in either NTSC or CCIR format and is compatible with multi-PCM.

First, the tape pattern shown in FIG.
A case of reproducing a tape recorded in the video signal recording mode will be described.

The reproduction signal extracted from the magnetic tape 1 by the rotary head 23a or 23b is amplified by the preamplifier 8 or 9,
Fig. 2 shows A and B. The amplified reproduced signals A and B are changed over by the control switch (S1 in FIG. 2 F1) from the controller 35.
W) Can be switched through 10,11. The output of SW10 (Fig. 2C) is one to the video signal reproduction processing system 21 and one to the band pass filter (BPF) 18 for extracting the FM audio signal,
One is input through the SW 38 to the automatic track finding processing circuit (ATF processing circuit) 22 and the system identification circuit 40 for identifying the NTSC / CCIR system. Since the tape recorded in the video signal recording mode is being reproduced, the SW 38 is connected to the V side according to a command from the controller 35. The output of SW11 (Fig. 2D) is PCM
Input to the signal reproduction processing circuit 32. Video signal reproduction processing system 21
The reproduction signal input to the filter block 12 is separated into a low-frequency conversion chromaticity signal and an FM modulation luminance signal by the filter block 12 and then extracted, and then a video signal reproduction process configured by the video signal processing circuit 13 and the oscillation circuit 15. The circuit performs FM demodulation of the luminance signal and reconversion of the chromaticity signal, and the demodulated video signal is output from the output terminal 14. Only the FM audio signal is extracted from the playback signal input to the BPF 18, and then the FM audio processing circuit (AFM processing) 19 performs FM demodulation into an audio signal, and the output terminal 20
Will be output. The ATF processing circuit 22 extracts a 4-frequency pilot signal from the reproduced signal for performing tracking servo, and the servo processing circuit 30 extracts the reproduced pilot signals obtained from both adjacent tracks so that the levels thereof are the same.
Control signal is output to.

FIG. 3 shows an example of a specific circuit configuration of the ATF processing circuit 22 and the pilot signal generating circuit 31. In FIG. 3, the input terminal 72
A reproduction signal from the magnetic tape 1 (Fig. 2C in the video signal recording mode, Fig. 2D in the multi-PCM mode) input from the magnetic tape 1 is reproduced by a bandpass filter (BPF) 73 and a reproduction pilot signal of four frequencies (NTSC ₁ ≈ ₁ 103KHz, ₂ ≒ 119KHz,
₍₃ ≈165 KHz, ₄ ≈149 KHz) is extracted, and the multiplier 74 multiplies the output signal of the pilot signal generating circuit 31 to perform frequency conversion. PBF75 and 7 from the output of multiplier 74
The components of about 16 KHz and about 47 KHz, which are proportional to the pilot signal levels obtained from both adjacent tracks, are separated and extracted by using 7, and the respective output levels are detected by the envelope detection circuits 76 and 78. The detected output is compared by the comparator 79, and the obtained output is sent from the output end 86 to the servo processing circuit 30 through the LPF 84 and the SW 85 when the video signal is being reproduced. SW80 and capacitor 8 when playing in multi-PCM mode
In the sample hold circuit composed of 1 and 1, the output of the comparator 79 is extracted only in the track section to be reproduced-for example, the section corresponding to B in FIG.
It is sent to the servo processing circuit 30 through 82, LPF 83 and SW85. Servo circuit according to the signal sent from the output terminal 86
At 30, the tracking servo is performed by controlling the capstan motor 29 so that the output of the comparator 79 becomes zero. Here, the signal for controlling the SW80 is the gate pulse signal (FIG. 2G) generated in the PCM signal reproduction processing circuit 32, and is the reference signal of the PCM signal reproduction processing circuit 32 in FIG.
Made from channel select signals that die to.

Next, the pilot signal generation circuit 31 will be described. Oscillator circuit 65: NTSC system 5.95MHz, CCIR system
It is configured to obtain an oscillation output of 5.86MHz,
It is switched by the output signal of the system identification circuit 40. The output signal of this oscillator circuit 65 is divided into 1/58, 1/50, 1/3 by frequency dividers 66 to 69.
By dividing the frequency by 6,1 / 40, pilot signals ₁ , ₂ ,
₃ and ₄ are obtained. These ₁ to ₄ pilot signals are sequentially switched to ₁ , ₂ , ₃ , ₄ by the output switching circuit 70 by the head switching signal (FIG. 2H) which is the output signal of the servo processing circuit 30 input from the input terminal 71. Output. Here, the head switching signal is created based on the signals obtained from the magnets 24a and 24b mounted on the cylinder and the pickup head 25.

In the servo processing circuit 30, the signals obtained from the magnets 24a and 24b and the pickup head 25 and the servo processing circuit are described.
The rotation speed of the cylinder motor 26 is controlled to be constant by comparing with the reference signal in 30. Further, the capstan motor 29 uses the output of the rotation speed signal generator composed of the FG 28 and the pickup head 27 attached to the motor to keep the rotation speed constant, and performs tracking with the output signal of the ATF processing circuit 22. ing. PCM signal reproduction processing circuit 3
In step 2, after equalizing the reproduced signal and identifying the data, P
The demodulated CM is demodulated and the demodulated voice signal is output from the output terminals 33 and 34.

A specific example of the PCM signal reproduction processing circuit 32 is shown in FIG. In FIG. 4, the reproduced signal input from the input terminal 63 is phased to the strobe circuit 54, one to the strobe circuit 54 after the intersymbol interference is removed by the waveform equalization circuit 49. It is output to a clock recovery PLL circuit which is composed of a comparator 51, a filter 52, and a voltage controlled oscillator (VCO) 53. The strobe circuit 54 reproduces data from the output signal of the waveform equalizing circuit 49 by the clock reproduced by the clock reproducing PLL circuit. The reproduced data which is the output of the strobe circuit 54 is input to the PCM processor 56 together with the reproduction clock, and the PCM processor 56 performs error correction, decoding and time axis expansion. A random access memory (RAM) 55 and a master clock generation circuit 57 are used to perform operations such as error correction, decoding and time base expansion. Also, the PCM processor is 30H in the NTSC system.
In the z and CCIR systems, 25 Hz is used as the reference signal (CH1 in Fig. 2), and in NTSC and CCIR, the control signal input from the input terminal 133 switches the frequency dividing circuit (not shown) in the PCM processor 56. ing. The reference signal (CH1 in FIG. 2) is input from the input terminal 64 to the PCM processor 56 and the master clock generation circuit 57.

The digital signal decoded by the PCM processor 56 and expanded on the time axis is converted into a digital-analog converter (D / A) 59.
Is converted back to an analog signal, that is, a voice signal. D / A5
After removing unnecessary band components from LPF 60 and 61, the output signal of 9 expands the dynamic range compressed at the time of recording to the original dynamic range by noise reduction (HR) 62, and outputs from output terminals 33 and 34. It is output as a reproduced audio signal. In the multi-PCM mode, the reference signals (CH1 to CH6 in Fig. 2) corresponding to each track are sent to the controller 35.
Is input through the input terminal 64. Further, the gate pulse (G1 to G5 in FIG. 2) corresponding to each track is output from the output terminal 132 from the PCM processor 56 and sent to the ATF processing circuit 22 and the system identification circuit.

By the way, the video signal reproduction processing system 21, the PCM signal reproduction processing circuit 32, the pilot signal generation circuit 31, and the servo processing circuit.
The 30 has different signal processing in NTSC and CCIR systems. For example, in the video signal reproduction processing system 21, the color burst signal frequency for chromaticity signal processing is 3.58 MHz for NTSC.
z, CCIR is 4.43MHz, and a chromaticity signal processing system for removing crosstalk from adjacent tracks,
In NTSC, it is called the phase inversion method (PI method), and in CCIR, it is the method called the phase shift method (PS method). The PCM signal reproduction processing circuit 32 and the servo processing circuit 30 operate with 30 Hz for NTSC and 25 Hz for CCIR as reference signals. In addition, the pilot signal generation circuit 31
The reference frequency is 5.95MHz for NTSC and 5.86MHz for CCIR.

Therefore, determine whether the tape being played is an NTSC system tape or a CCIR system tape,
It is necessary to switch the signal processing circuit. This determination is made by the system identification circuit 40, and in this embodiment, when the pilot signal frequency in the reproduction signal is a tape recorded by the NTSC system and reproduced by the CCIR system,
The fact that the tape recorded by the IR system is reproduced by the NTSC system is used. Hereinafter, a specific example will be described with reference to FIG. In case of 4 frequency pilot signal-NTSC for tracking servo, ₁ ≒ 102.55KHz, ₂ ≒ 118.95KHz, ₃ ≒ 165.20KH
Let z, ₄ ≈ 148.69 KHz- be used. The frequency of the reproduction pilot signal when the tape recorded by the NTSC system is reproduced by the CCIR system and when the tape recorded by the CCIR system is reproduced by the NTSC system, the cylinder rotation speed is 25 Hz (CCIR), 30 Hz (HTSC ), The values are as shown in Table 1.

In FIG. 3, the system identification circuit 40 is a tank circuit 106.
-Center frequency Q = 20-Tank circuit 117-Center frequency 85.55KHz, Q = 2
0-peak detection circuit 107, 118, hold circuit 108, 119, level identification circuit 109, 120 and SW 114, voltage source (V _B ) 113, and state determination circuit 41. Now, assume that the video tape recorder shown in FIG. 1 is operating as a CCIR system. If a video signal recording mode tape recorded by the NTSC system is reproduced by this video tape recorder, it is input from the input terminal 72. SW10 when playing from magnetic tape 1
Is an output signal of and is input to the tank circuits 106 and 117. Here, since the frequency of the pilot signal in the reproduced signal is the frequency shown in Table 1, _one pilot signal is extracted from the tank circuit 117.
No pilot signal is extracted from 106.

The outputs of the tank circuits 106 and 107 are peak detection circuits 107 and 118.
After being detected by and passed through the hold circuits 108 and 119, presence / absence (“1” / “0”) of the pilot signals of the tank circuits 106 and 117 is identified by the level identifying circuits 109 and 120. Therefore, in the above case, since the pilot signal is extracted from the tank circuit 117, “1” is output from the level identification circuit 120 and “0” is output from the level identification circuit 109. The SW 114 operates in response to a control signal indicating the multi-PCM mode input from the input terminal 112 and is in the video signal recording mode as described above, and therefore is connected to the V side. Therefore, the control signals of the hold circuits 108 and 119 are constant with the DC voltage source V _B, and are always in a conducting state. Level identification circuit 10
The output of 9.120 is input to the status determination circuit 41, and the signal on the playback tape is NTSC system or CCIR according to the above output signal.
Depending on whether it is a system or not, the output terminal 115 outputs a “0” signal in the NTSC system and a “1” signal in the CCIR system. The relationship between the output signals of the level discriminating circuits 109 and 120 and the output signal of the state discriminating circuit 41 is as shown in Table 2.

Therefore, in the above example, "0" is output from the output terminal 115 so as to switch to the NTSC system.

According to the output signal (“0” / “1”) of the output terminal 115, the video signal reproduction processing system 21 oscillates 3.58 MHz (NTSC) and 4.43 MHz (CCIR) for the chromaticity signal reproduction processing as described above. The crystals 16 and 17 are switched, and further the inside of the video signal processing circuit 13 is switched to the PI system (NTSC) and the PS system (CCIR). Servo processing circuit 30: NTSC reference signal 30Hz, CC
The oscillation frequency of the reference oscillation circuit (not shown) and the frequency dividing circuit (not shown) are switched so that the frequency becomes 25 Hz at IR. PC
Since the M signal reproduction processing circuit 32 performs the system operation by using the reference signal of 30 Hz at NTSC and 25 Hz at CCIR, the frequency dividing circuit (not shown) in the PCM processor 56 is switched. Also,
The pilot signal generation circuit 31 switches the oscillation crystals 121 and 122 of the reference oscillation circuit 65 to 5.95 MHz at NTSC, CCIR
The time is set to 5.86MHz.

Next, in the video tape recorder shown in FIG.
For playing the tape pattern shown in the figure, that is, the tape recorded in the multi-PCM recording mode,
The operation of the system identification circuit 40 will be described with reference to FIG.

When reproducing the tape recorded in the multi PCM recording mode, the SW 38 is connected to the M side by the instruction of the controller 35. Also, SW10 and 11 are switched by F1 and F2 in Fig. 2,
When the areas shown in FIGS. 13B to 13F are reproduced, they are switched by F2. Therefore, the ATF processing circuit 22 and the system identification circuit 40 have S
The output signal of W11 (D1 to D6 in Fig. 2) is input. Input end 72
From the reproduction signals of D1 to D6 in Fig. 2 input from the tank circuit 10
The pilot signal is extracted at 6,117. For example, VTR is NT
If the tape that is operating as the SC system and is to be played back is recorded by the CCIR system, the frequency of the pilot signal in the playback signal (D1 to D6 in Fig. 2) is as shown in Table 1. Yes, the pilot signals are not extracted from the tank circuits 106 and 117. Tank circuit 106,117
After the output of is detected by the peak detection circuits 107 and 118,
In order to extract only the signal of the track area to be reproduced-for example, the D2 signal section in FIG. 2 corresponding to B in FIG. 13, the hold circuits 108 and 119 perform the hold processing. The hold circuits 108 and 119 receive the second signal from the input terminal 111.
It operates with the gate pulse signal shown in Figure G2.

The outputs of the hold circuits 108 and 119 identify the presence or absence of the pilot signal extracted by the tank circuits 106 and 117 by the level identifying circuits 109 and 120, and the level identifying circuits 109 and 120 output "1" when there is a pilot signal and "0" when there is no pilot signal. To do. In the above example, since the pilot signals are not extracted by the tank circuits 106 and 117, the outputs of the level identification circuit 109.120 are both "0".
Becomes Further, since the operation of the state discrimination circuit 41 is as shown in Table 2, "1" for instructing switching to the CCIR system is output from the output terminal 115.

As described above, in the multi-PCM mode, the pilot signal of only the recording track section to be reproduced is used to identify whether the tape to be reproduced is recorded by the NTSC system or the CCIR system.

FIG. 5 shows another specific example of the system identification circuit 40. In FIG. 5, the system identification circuit 40 is a tank circuit 123-
Center frequency 195KHz, Q = 20-, tank circuit 128-Center frequency 85.55KHz, Q = 20-, peak detection circuit 124,12
9 and hold circuits 125 and 130 and level identification circuits 126 and 131 and SW1
14 and voltage source (V _B ) 113 and RS flip-flop (RS-F.
F.) 127 and. Here, when the tape recorded by the NTSC system is reproduced while the video tape recorder is operating as the CCIR system, the pilot signal frequency in the reproduced signal has the values shown in Table 1. Therefore, the tank circuit 128 is more
₁ to ₁ are extracted, but the pilot signal is not extracted from the tank circuit 123. Furthermore, the outputs of the tank circuits 123 and 128 are the peak detection circuit 12
After being detected by 4,129, it is input to the level identification circuits 126, 131 through the hold circuits 125, 130. Level identification circuit 12
At 6,131, the presence or absence of the pilot signal extracted from the tank circuits 123 and 128 is identified, and "1" is output when the pilot signal is present, and "0" is output when the pilot signal is absent. Therefore, in the above case, the output of the level identification circuit 126 is "0", the output of the level identification circuit 131 is "1", and RS-FF127 is reset,
Output "0" from the output terminal 110 to switch each block to the NTSC system. In addition, when a tape recorded by the CCIR system is applied while the video tape recorder is operating in the NTSC system, Table 1 shows that the pilot signal is output only from the tank circuit 123. The output is "1", the output of the level identification circuit 131 is "0", RS-FF is set, and "1" is output from the output terminal 110. The output signal from the output terminal 110 switches each block to the CCIR system.

Further, when the video tape recorder operating system and the tape to be reproduced have the same signal format, the outputs of the level identification circuits 126 and 131 are both "0", and RS
-There is no change in the output state of FF127, so the system is not switched.

Table 3 below summarizes the relationship between the outputs of the level identification circuits 126 and 131 and the output of the RS-FF 127.

Here, the hold circuits 125 and 130 are the same as those described in FIG. 3, and when the tape recorded in the multi-PCM recording mode is reproduced, only the pilot signal of the track to be reproduced is used, Only the track section to be reproduced becomes conductive. The control signals of the hold circuits 125 and 130 are input from the input terminal 111.
The signals are as shown in G1 to G5.

FIG. 6 shows another specific example of the system identification circuit 40. In FIG. 6, the system identification circuit 40 is a tank circuit 137-
Center frequency 85.55KHz, Q = 20-, and tank circuit 138-
Center frequency 164KHz, Q = 20-, tank circuit 139-Center frequency 195KHz, Q = 20-, peak detection circuit 140, 14
1, 142, hold circuits 143, 144, 145, a level comparator 146, a state determination circuit 147, a SW 114, and a voltage source (V _B ) 113. Here, when the tape recorded by the NTSC system is reproduced while the video tape recorder shown in FIG. 1 is operating as the CCIR system, the pilot signal frequency in the reproduced signal becomes the value shown in Table 1. Therefore,
The tank circuit 137 extracts the pilot signal ₁ from the reproduction signal input from the input terminal 72, and the tank circuit 138 and the tank circuit 139 do not extract the pilot signal, but 164 KHz.
And noise components around 195 KHz are extracted. Tank circuit
The outputs of 137, 138 and 139 are detected by peak detection circuits 140, 141 and 142 and then input to hold circuits 143, 144 and 145.
The output of the hold circuits 143, 144, 145 is 3 by the level comparator 146.
Two levels P (hold circuit 143), Q (hold circuit 1
44) and R (hold circuit 145) are compared, and the level comparator 146 outputs a signal indicating the maximum level of P, Q, and R to the state determination circuit 147. The state discriminating circuit 147 discriminates between NTSC and CCIR systems by the output of the level comparator 146, and outputs "0" from the output terminal 148 in the case of the NTSC system and "1" in the case of the CCIR system. The relationship between the level comparator 146 and the state discrimination circuit 147 is as shown in Table 4.

Therefore, in the above example, since the level comparator 146 outputs "P" to the state determination circuit 147, from Table 4, the output terminal 148 outputs "0".
Is output, and each block of FIG. 1 is switched to the NTSC system according to this output signal. The hold circuit
143, 144, and 145 are the same as those described in FIG. 3 and FIG. 5, and when reproducing a tape recorded in the multi-PCM recording mode, the reproduction is performed because only the pilot signal of the track to be reproduced is used. Only the track section to be tried becomes conductive. This hold circuit 143,144,14
The control signal 5 is a signal input from the input terminal 111 as shown in G1 to G5 in FIG.

The system identification method using the reproduction frequency of the pilot signal has been described above using three examples. However, other methods such as a method of setting the center frequencies of the tank circuits to 164 KHz and 195 KHz and a tank circuit of the center frequency 165 KHz are described. There are many possible methods for use, but it is obvious that any configuration may be used as long as it uses the reproduction frequency of the pilot signal.

Next, another embodiment of the present invention is shown in FIG. In FIG. 7, it has the same function as the VTR shown in FIG. 1, the same circuits are given the same numbers, and the description thereof is omitted. The difference between FIG. 7 and FIG. 1 is that the reproduced PCM signal is used to identify in which system, NTSC or CCIR, the tape to be reproduced is recorded. That is, the tape reproduced by the system identification circuit 44 is NT by using the PCM signal and the gate pulse signal (G1 to G5 in FIG. 2) obtained from the PCM signal reproduction processing circuit 32.
Whether it is recorded by the SC system or the CCIR system is identified, and the servo processing circuit 30 is selected according to the identification result.
A video signal reproduction processing system 21, a pilot signal generation circuit 31,
The PCM signal reproduction processing circuit 32 can be switched to the NTSC or CCIR system.

FIG. 8 shows a specific configuration example of the system identification circuit 44. In FIG. 8, the reproduced PCM signal (D1 to D6 in FIG. 2) input from the input terminal 63 is subjected to intersymbol interference and the like in the waveform equalization circuit 49. One of the output signals of the waveform equalization circuit 49 is input to the strobe circuit 54, and one is input to the gate circuit 87 which constitutes the system identification circuit 44. Here, as shown in FIG. 9, the PCM signal of the 8 mm video standard is mainly composed of three parts, a preamble part, a data part and a postamble part, and the preamble part has a clock used for data reproduction. “1” data for easy playback, ie 5.79MHz for NTSC system and 5.75MHz for CCIR system
The signal of is recorded.

An example of a specific circuit configuration shown in FIG. 8 is a method of identifying the NTSC system or the CCIR system by identifying the reproduction frequency of the signal of the preamble part. Gate circuit 87
Then, of the output signal of the waveform equalizing circuit 49, only the portion corresponding to the preamble portion shown in FIG. 9 is extracted.
The signal of the preamble portion extracted by the gate circuit 87 is input to the tank circuits 88 and 93. The tank circuit 88 has a center frequency of 4.83 MHz, Q = 20, and the tank circuit 93 has a center frequency of 6.8.
It has the characteristics of 7MHz and Q = 20.

By the way, the frequency of the signal in the preamble part is 5.79 MHz in the NTSC system and 5.7 in the CCIR system as described above.
Since it is 5MHz, the video tape recorder (VTR) is NTSC
Depending on whether the system is operating or the CCIR system, the reproduction signal frequency of the preamble part has the values shown in Table 5.

Therefore, assuming that the VTR is operating in the NTSC system and the tape to be played back is recorded in the CCIR system, from Table 5, the tank circuit 93 can extract the signal of the preamble portion, and the tank circuit 88 outputs I can't get a signal. After the outputs of the tank circuits 88 and 93 are detected by the peak detection circuits 89 and 94, the detection outputs are extracted by the hold circuits 90 and 95 only during the period corresponding to the preamble part. Hold circuit 9
The output of 0,95 is output to tank circuits 88,93 by level identification circuits 91,96.
The presence / absence of the output signal is identified, and the level identification circuits 91 and 96 output "1" when the signals of the preamble part are extracted by the tank circuits 88 and 93, and output "0" when they are not extracted. The outputs of the level identification circuits 91 and 96 are input to RS-FF127, it is determined whether the tape to be played back is the NTSC system or the CCIR system, and the result is output from the output terminal 97. The relationship between the outputs of the level discriminating circuits 91 and 96 and the output of RS-FF is as shown in Table 6. In the case of NTS system, "0", C
In the CIR system, "1" is output from the output terminal 97.

In the above example, from Table 6, “1” is output from the output terminal 97,
Depending on this output signal, each block shown in Fig. 7 is CCIR
Switched to the system.

The gate circuit 87 and the hold circuits 90 and 95 are gate pulse signals output from the PCM preset 56 (G1 to G5 in FIG. 2).
, And operates with the output signal of the timing pulse generation circuit 134 which generates a timing pulse having a pulse width of a period corresponding to the preamble portion.

The input signal to the gate circuit 87 may be a reproduction signal input from the input terminal 63. FIG. 10 shows another specific configuration example of the system identification circuit 44. In FIG. 10, the same numbers are assigned to the same operation circuits as in FIG. The tank circuit 135 has a center frequency of 5.77 MHz and Q = 20. The reproduced PCM signal (D1 to D6 in FIG. 2) inputted from the input terminal 63 is inputted to the gate circuit 87 constituting the system identification circuit 44.
The gate circuit 87 extracts only the part corresponding to the preamble part shown in FIG. 9 from the output signal of the waveform equalization circuit 49. The signal of the preamble portion extracted by the gate circuit 87 is input to the tank circuit 135.

Now, assuming that the VTR operates as the NTSC system and the tape to be played is recorded by the CCIR system, the signal cannot be extracted from the tank circuit 135 from Table 5. The output of the tank circuit 135 is detected by the peak detection circuit 89, and then the detected output is extracted by the hold circuit 90 only during the period corresponding to the preamble portion. With respect to the output of the hold circuit 90, the level identification circuit 91 identifies the presence or absence of the output signal of the tank circuit 90, and the level identification circuit 91 outputs "1" when the signal of the preamble portion is extracted by the tank circuit 90, When not extracted, "0" is output. The output of the level discriminating circuit 91 is input to the state discriminating circuit 136 to discriminate whether the tape to be reproduced is the NTSC system or the CCIR system. State determination circuit 13
The operation of 6 is as shown in Table 7, and outputs "0" from the output terminal 92 in the NTSC system and "1" in the CCIR system.

In the above example, since the VTR operates as an NTSC system, "0" was output from the output terminal 92, but the output state of the state determination circuit 136 is inverted from Table 7 as a result of the tape identification, so the output "1" will be output from the end 92, and each block shown in FIG. 7 will be switched to the CCIR system. The input signal to the gate circuit 87 is
The output signal of the waveform equalization circuit 49 may be used.

Next, FIG. 11 shows another specific circuit example of the system identification circuit 44. In FIG. 11, the system identification circuit 44 is composed of level identification circuits 99 and 100, hold circuits 101 and 102, and RS-FF127. The level discriminating circuits 99 and 100 are supplied with the control signal of the VCO 53 of the clock recovery PLL circuit composed of the doubling circuit 50, the phase comparator 51, the filter and the VCO 53.
The frequency of the clock reproduced by the above clock reproduction PLL circuit is 11.58MHz in the NTSC system and 11.5MHz in the CCIR system.
Since it is MHz, the frequency of the clock becomes the value shown in Table 8 depending on whether the video tape recorder is operating in the NTSC system or the CCIR system. Therefore, the control signals of the VCO 53 corresponding to the values in Table 8 are obtained, and the DC potential of each control signal becomes a value as shown in Table 9, for example.

Here, the identification level of the level identification circuit 99 is set to 2.25V, the identification level of the level identification circuit 100 is set to 2.75V, and when the input level is lower than the identification level of the level identification circuit 99, or the identification level of the level identification circuit 100. It is assumed that each level identification circuit 99, 100 outputs "1" when the value is larger. The relationship between the operation system of the video tape recorder and the output of RS-FF127 is as shown in Table 10. In the CCIR system, "1" is output, and in the NTSC system, "0" is output from the output terminal 103.

Therefore, if the video tape recorder operates as an NTSC system and the tape recorded by the CCIR system is played back, the level identification circuit 100 outputs "1", and this output signal passes through the hold circuit 102. , RS-FF127 are set, "1" is output from the output terminal 103 and each block shown in FIG. 7 is switched to the CCIR system.

The hold circuits 101 and 102 operate on the gate pulse signals (G1 to G5 in FIG. 2) output from the PCM processor 56.

The system identification method using the PCM signal has been described above using three embodiments, but it is obvious that other configurations may be used.

〔The invention's effect〕

According to the present invention, as described in the above embodiment, NTSC
Whether it is a tape recorded by either the system or the CCIR system, a simple circuit configuration can surely identify the recording system and switch the reproduction system corresponding to it. Its effects are great, such as the fact that the recorder can be used for many purposes.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a video tape recorder of the present invention, FIG. 2 is a signal waveform diagram of each part of FIG. 1, and FIG. 3 is a block diagram showing a concrete configuration of an ATF processing circuit. FIG. 4 is a block diagram of a PCM signal processing circuit, FIG. 5 is a block diagram showing another embodiment of the system identification circuit, FIG. 6 is a block diagram showing another embodiment of the system identification circuit, and FIG. FIG. 8 is a block diagram showing another embodiment of the video tape recorder of the invention, FIG. 8 is a block diagram showing another embodiment of the system identification circuit, FIG. 9 is a development view of a recording signal, FIG. 10, FIG.
FIG. 11 is a block diagram showing another embodiment of the system identification circuit, and FIGS. 12 and 13 are recording pattern diagrams of signals of a conventional video tape recorder. 40,44 …… System identification circuit 88,93,106,117,123,128,135,137,138,139 …… Tank circuit 89,94,107,118,124,129,140,141,142 …… Peak detection circuit 90,95,108,119,125,130,143,144,145,101,102 …… Hold circuit 127 …… RS-flip-flop 41,136,147 …… State discrimination circuit 56 …… PCM processor 35… …controller

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Kaniwa 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture Home Appliances Research Laboratory, Hitachi, Ltd. (56) References

Claims (2)

[Claims] 1. A helical scan video having means for forming recording tracks tilted at a constant angle with respect to the longitudinal direction of a magnetic tape, and means for sequentially multiplex-recording tracking control signals having different frequencies on the tilted recording tracks. In a tape recorder, a specific frequency component is extracted by inputting the tracking control signal reproduced by the means for reproducing the tracking control signal having the different frequency from the reproduction signal of the magnetic tape and the means for reproducing the tracking control signal. Means, means for detecting the signal extracted by the means for extracting the specific frequency component, means for holding the output from the means for detecting, and recording on the magnetic tape based on the output of the holding means. Means for identifying the recording method used, and for identifying the above recording method A video tape recorder having means for switching a reproduction processing circuit according to a recording system based on an output from the means. 2. A helical scan type video tape recorder having means for forming recording tracks inclined at a constant angle with respect to the longitudinal direction of the magnetic tape, and means for recording PCM signals on the inclined tracks. Based on the PCM signal reproduced by the means for reproducing the PCM signal recorded in the above, and the PCM signal reproduced by the means for reproducing the PCM signal, a PLL (phase locked loop) system composed of a phase detection means, a loop filter and an oscillation circuit Means for reproducing the clock, level identifying means for identifying the level of the control signal of the oscillation circuit, holding means for holding the output of the identifying means, and recording for identifying the recording system based on the output of the holding means. Based on the output of the system identification means, the recording system identification means, the frequency division ratio and servo frequency of the PCM signal processing circuit corresponding to the recording system. A video tape recorder having a switching means for switching a frequency division ratio of a path.