JPS6213740B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a helical scan type magnetic recording/reproducing apparatus (VTR), which enables recording with good continuity when recording a new signal following an already recorded magnetic tape. It is configured so that it can be done.

On a VTR, pause the recording state and
Next, when you cancel the pause and put the tape into recording mode and play back the spliced tape, the playback screen will be distorted because the control signals recorded at the splice section are not continuous. Therefore, when the pause occurs, the tape is rewound a little, and the capstan is controlled by the playback control signal for a while after the pause is released, so that the control signal to be newly recorded and the playback control signal are in the same phase. The continuity of the control signals recorded on the tape may be ensured by transitioning to the recording state in the same state.

A block diagram of a conventional method of driving a capstan shaft from a capstan motor via a belt is shown in FIG. 1, and a timing chart of each part is shown in FIG. 2. This will be explained below with reference to the figures.

In FIG. 1, 1 is a cylinder motor 1 on which a video head is attached to its shaft.
2 is a phase detection head 2 for detecting the position of the video head.

The output of the phase detection head 2 is input to a phase detection processing circuit 4 which shapes the waveform and sets the position of the video head through a delay circuit (not shown). The output of the phase detection processing circuit 4 becomes the signal _S1 ,
The signal is input to the recording phase adjustment circuit 5, where phase adjustment is performed between the vertical synchronization signal of the recording video signal and the video head, and its output becomes a signal _S2 , which is input to the cylinder phase comparison circuit 9. On the other hand, the vertical synchronization signal in the video signal to be recorded is separated by a vertical synchronization separation circuit 6 to become a signal _S3 , which is input to a 1/2 frequency divider circuit 7, where it is rotated by 1/2 to become a signal _S4 . The signal S ₄ is input to the cylinder trapezoidal wave shaping circuit 8, and its output becomes the signal S _5. The cylinder phase comparison circuit 9 compares the phases of the signal S ₂ and the signal S ₅ , and the error signal is input to the cylinder motor drive circuit 11. do. In addition, a signal detected by the frequency generator 3 that detects the rotation speed of the cylinder motor 1 is transmitted to the cylinder speed control circuit 10.
input the speed detection error signal to the cylinder motor drive circuit 11, and input the speed detection error signal to the cylinder motor drive circuit 11.
The cylinder motor 1 is controlled by the output signal. Also, from the capstan motor 12 to the belt 14
The capstan shaft 15 is rotated to transfer the tape 16. The control signal reproduced by the control head 17 passes through the switching SW 19 (the SW is set to the b side at the beginning of the connection), and is amplified through the reproduction control amplifier 20 to become a signal _S9 . The signal detected by the frequency generator 13 that detects the rotation speed of the capstan motor 12 is waveform-shaped by a waveform shaping circuit 21.
The signal is input to the frequency divider circuit 22 with a set terminal. When the playback control signal _S9 is input to the set input terminal, a signal _S8 synchronized with the playback control signal is output. The signal S ₈ is input to the capstan recording tracking circuit 23 and is delayed to become the signal S ₇
Output. The signal S ₄ is input to the capstan trapezoidal wave generating circuit 24 and the signal S ₆ is output. Signals S ₆ and S ₇ are input to the capstan phase comparison circuit 25 and compared in phase, and a phase comparison error signal is input to the capstan drive circuit 27. In addition, the output signal of the waveform shaping circuit 21 is transmitted to the capstan speed control circuit 26.
The speed control error signal is input to the capstan drive circuit 27, and its output controls the capstan motor 12. As described above, the cylinder phase circuit compares the vertical synchronization signal of the video signal to be recorded and the phase of the video head.
In the capstan phase circuit, the vertical synchronization signal of the video signal to be recorded and the control signal recorded on the tape are compared in phase, so when the servo rise time has elapsed after the pause is released, the playback control signal and the control signal to be recorded are compared. (signal S ₄ obtained by dividing the vertical synchronization signal of the video signal to be recorded by 1/2) is in the same phase, and in this state, by changing the switching SW 19 from side B to side A, the signal is recorded on the tape. Since the continuity of the control signal can be maintained, the image will not be distorted when the spliced portion is played back.

Next, we will discuss the case of using the direct drive capstan method. In this case, the problem is how to adjust the tape speed. In the case of a direct drive capstan, the tape speed during recording is determined approximately by the shaft diameter of the capstan and the rotational speed of the capstan. Therefore, in order to absorb variations in the capstan shaft diameter, it is necessary to slightly change the frequency of the reference signal of the capstan phase comparator circuit during recording (with conventional belt drives, the thickness of the belt is changed to adjust the tape speed). I was making corrections.) Therefore, the reference signal of the capstan phase comparator circuit during recording cannot be the conventional vertical synchronization signal of the video signal to be recorded. Therefore, a signal obtained by frequency-dividing the color subcarrier (3.58 MHz in the case of NTSC) is used as a reference signal for the capstan phase comparator circuit during recording. In this case, the reference signal of the cylinder phase comparator circuit during recording (vertical synchronization signal of the video signal to be recorded) and the reference signal of the capstan phase comparator circuit are different, so there is no continuity of the control signal at the joint. If this part is played back, the image will be distorted.

Therefore, a block diagram of the connection in the direct drive capstan of the present invention is shown in FIG. 3, and a timing chart of each part during connection is shown in FIG. 4.
This will be explained below with reference to the figures.

In FIG. 3, the cylinder control system is unchanged from the conventional example shown in FIG. The capstan control system transfers the tape 16 by rotation of a direct drive capstan motor 30. control head 17
The control signal reproduced in is amplified through the switching SW 19 (SW is set to the b side at the start of connection) and the reproduction control amplifier 20, and becomes a signal _S9 . The signal detected by the frequency generator 13 that detects the rotation speed of the capstan motor 30 is waveform-shaped by a waveform shaping circuit 21.
The signal is input to the frequency divider circuit 22 with a set terminal. When a playback control signal is input to the set input terminal, a signal _S8 synchronized with the playback control signal is output. The signal _S8 is input to the capstan recording tracking circuit 23, which outputs a delayed signal _S7 . On the other hand, the oscillation frequency (3.58 MHz in the case of NTSC) is inputted from the color subcarrier oscillation circuit 32 to the frequency dividing circuit 33 with a set terminal. By differentiating and inputting the signal _S4 , which is obtained by dividing the vertical synchronizing signal of the video signal to be recorded by 1/2, into the set input terminal, the output of the frequency divider circuit 33 with the set terminal is a signal synchronized with the signal _S4 . S ₁₁ (switching SW 31 is on the b side). Signal S ₁₁ is capstan trapezoidal wave creation circuit 2
4 and outputs a signal _S6 . Signals S ₆ and S ₇ are inputted to the capstan phase comparison circuit 25 and compared in phase, and a phase comparison error signal is inputted to the capstan drive circuit 27. The output signal of the waveform shaping circuit 21 is input to a capstan speed control circuit 26, and the speed control error signal is applied to a capstan drive circuit 27, which controls a capstan motor 30 with its output.

As described above, the cylinder phase comparison circuit compares the vertical synchronization signal of the video signal to be recorded and the phase of the video head, and the capstan phase comparison circuit compares the vertical synchronization signal of the video signal to be recorded and the phase of the video head to be recorded on the tape. Since the control signals are phase-compared, when the servo rise time elapses after the pause is released, the playback control signal and the control signal to be recorded (signal S ₄ which is the vertical synchronization signal of the video signal to be recorded divided in half) ), and in this state the switching switch
19. By changing the switching SW 31 from the b side to the a side, the continuity of the control signals recorded on the tape can be maintained, so that when the spliced portion is played back, the image will not be distorted.

If you use the above method, there is no need to bring the reference signal of the capstan phase control system during recording with the vertical synchronization signal of the video signal to be recorded, so you can freely change the shaft diameter of the capstan and the frequency of the frequency generator. TV signals with different vertical synchronization signals (NTSC60H series, PAL/SECAM50Hz)
system), by changing the frequency dividing ratio of the frequency dividing circuit 22 with set terminal and the frequency dividing circuit 33 with set terminal, the direct drive capstan motor 30 and the frequency generator 1 can be
3 can be shared.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a VTR using a conventional belt-driven capstan, Fig. 2 is an explanatory diagram of the same operation, Fig. 3 is a block diagram showing one embodiment of the present invention, and Fig. 4 is an explanatory diagram of the same operation. It is. 1... Cylinder motor, 2... Phase detection head, 3, 13... Frequency generator, 4... Phase detection processing circuit, 5... Recording phase adjustment circuit, 6... Synchronization separation circuit, 7... Frequency division 8... Trapezoidal wave shaping circuit, 9, 25... Phase comparator, 10... Speed control circuit, 11... Motor drive circuit, 16... Capstan, 17... Control head, 19, 3
1...Selector switch, 20...Amplifier, 21...
Waveform shaping circuit, 22... Frequency divider with set terminal, 2
3... Tracking circuit, 24... Trapezoidal wave shaping circuit, 25... Phase comparator, 26... Capstan speed control circuit, 27... Capstan drive circuit,
32... Color printing carrier wave oscillation circuit, 33... Frequency dividing circuit with set terminal.

Claims (1)

[Claims] 1 It has a cylinder with a rotating video head and a capstan that drives the magnetic tape. During recording, a signal that is phase-synchronized with the vertical synchronization signal of the video signal to be recorded is recorded on the magnetic tape as a control signal, and during playback, this In a magnetic recording/playback device that controls the rotation of a capstan so that the video head traces a recording pattern using a control signal, the capstan is directly connected to the shaft of the capstan motor and phase-synchronized with the control signal recorded on the tape. When recording the next new video signal on tape, the capstan phase control reference signal is forcibly set and phase synchronized with a signal that is phase-synchronized with the vertical synchronization signal of the video signal to be recorded for a predetermined period. By forcibly setting the capstan phase controlled signal with the playback control signal and synchronizing the phase,
When the playback control signal and the control signal to be recorded are in the same phase, a transition is made to the recording mode, and in the recording mode, the campus phase control is performed using a signal whose phase is synchronized with the vertical synchronization signal of the video signal to be recorded. 1. A magnetic recording and reproducing apparatus characterized in that the phase synchronization of a reference signal is canceled and the phase synchronization of a capstan phase controlled signal is canceled with a reproduction control signal.