JPH0442455A - Video tape recorder - Google Patents

Abstract

PURPOSE:To enable a fine pitch control without deteriorating the picture quality by conforming a locus of a head to a direction of a recording track and changing the relative speed between the head and a tape. CONSTITUTION:A moving speed of the rotary head and a traveling speed of the tape 8 is controlled in synchronization with a reference clock signal by a servo circuit part 1, and an output frequency of a frequency variable oscillator 2 is changed to be increased by (1+alpha) times, so as to increase the rotating speed of a cylinder and the traveling speed of the tape both by (1+alpha) times, thus changing the relative speed between the tape and the head to be (1+alpha) times its speed to keep the rotary head always under the state of tracing exactly on a recording track. Then, in accordance with this, a horizontal synchronizing signal frequency is multiplied by (1+alpha), whereas a comb line filter 3 is always normally operated even when the horizontal synchronizing signal frequency is changed by multiplying a delay amt. of a variable delay line 4 by (1+alpha). By this method, the reproducing under the pitch control for changing slightly the relative speed between the head and the tape is feasible.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video tape recorder in which the playback pitch can be finely adjusted.

Conventional technology In recent years, video tape recorders have been equipped with special playback functions such as picture search and slow playback, as well as 1.5x or 2x speed.
Convenient functions such as a double-speed playback function are being added when you want to view recorded content in a short time.

The special playback method for conventional video tape recorders is to first change the running speed of the tape, and then correct the rotational speed of the cylinder so that the horizontal synchronization frequency of the reproduced video signal does not change too much. there were.

Problems to be Solved by the Invention However, in the conventional video tape recorder as described above, for example, when you want to match the length of the video and BGM when dubbing the BGM during editing, or when you want to match the length of the audio signal to be played, If you want to make the pitch a little higher or lower, there was a problem that you could not do it because it did not have a pitch control function like an audio tape recorder.

The reason for this will be explained using FIG. 2. Figure 2 shows the moving speed of the rotating head, that is, the rotational speed of the cylinder (a), the running speed of the tape (b), and the trajectory of the head on the tape (
The relationship C) is shown as a vector. Same figure (I)
indicates the relationship between the champions during normal playback. Head trajectory (C)
coincides with the direction of the recording track.

Figure (n) shows double speed playback, that is, the tape running speed is 2x.
Shows the relationship between the champions when doubled. In the conventional special playback system for video tape recorders, the rate of change in the rotational speed of the cylinder is much smaller than the rate of change in the tape running speed, so the trajectory of the rotating head on the tape (C)
does not coincide with the direction of the recording track as shown in the figure, and extends over multiple recording tracks.

Therefore, when the running speed of the tape is slightly changed within the range of a few percent of the normal speedometer, the relationship between the trajectory of ``F'' and ``C'' and the recording track on the tape is similar to that shown in Figure 2 (II). Although it is different, a similar phenomenon occurs, and it becomes the same state as when tracking is off. In this state, since the head also traces adjacent tracks with different recording azimuth angles, the amplitude of the output signal from the head becomes smaller than during normal playback, and the S
/N ratio deteriorates. This degree increases as the tape running speed deviates from the normal speed, and the quality of the reproduced video signal deteriorates accordingly.

Figure 2 (III) shows the case where both the rate of change in the rotational speed of the cylinder and the rate of change in the tape running speed are doubled, on a scale of 172 as in Figures (I) and (n). be. If the rate of change in the rotational speed of the cylinder and the rate of change in the tape running speed can be made equal in this way, the trajectory of the head (C) will match the direction of the recording track, and the relative speed between the head and the tape will change at an equal rate. Change it with (
It is possible to change the pitch (doubled in the figure), which was not possible with conventional video tape recorders.

The present invention solves the above-mentioned conventional problems, and is shown in Fig. 2 (
As shown in III), by aligning the head trajectory (C) with the direction of the recording track and changing the relative speed between the head and tape, it is possible to avoid deterioration of image quality (
The purpose of the present invention is to provide a video tape recorder capable of fine pitch control.

Means for Solving the Problems In order to achieve this object, the video tape recorder of the present invention includes a servo circuit section that controls the rotational speed of the cylinder and the running speed of the tape, and a variable delay unit that can control the amount of delay from the outside. a line comb filter using a line; a variable frequency oscillator that supplies a reference clock signal to the servo circuit and a delay amount control signal to the variable delay line; and a control means for controlling the output frequency of the variable frequency oscillator. It is equipped with

Effect of the present invention With the above-described configuration, the output frequency of the variable frequency oscillator is changed by (1+α) times (however, 1α1<<1), so that both the cylinder rotational speed and the tape running speed are (
By increasing the speed by a factor of 1+α), the relative speed between the tape head is changed by a factor of 1+α, and a state in which the rotary head always properly traces the recording track (hereinafter referred to as an on-track state) is maintained.

Additionally, the horizontal synchronization signal frequency increases by (1+α), but the delay amount of the variable delay line is increased by (1+α),
The line comb filter always operates normally even if the horizontal synchronizing signal frequency changes.

Embodiment A video tape recorder which is a first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of a video tape recorder which is a first embodiment of the present invention. In Figure 1,
1 is a servo circuit section, 2 is a variable frequency oscillator, and 9 is a video signal processing section. 3 is a line comb filter, which consists of a variable delay line 4 and a subtracter 5.

The variable frequency oscillator 2 oscillates a signal with a frequency corresponding to the output voltage of the volume control means 6, and supplies the servo circuit section 1 with a reference clock signal and the variable delay line 4 with a control signal for determining the amount of delay.

A specific example of the variable frequency oscillator 2 is a VCO (voltage controlled oscillator).

The servo circuit section 1 controls the rotational speed of the cylinder, that is, the moving speed of the rotary head 7 and the running speed of the tape 8 in synchronization with a reference clock signal. Therefore, if the frequency of the reference clock signal increases by (1+α), both the moving speed of the rotary head 7 and the running speed of the tape 8 increase by (1+α). Therefore, the rotary head 7 can maintain an on-track state.

The reproduced signal from the rotary head 7 is processed in a video signal processing section 9 by dividing it into a luminance signal and a color signal. Among these, the color signal is
Since it contains crosstalk from adjacent tracks, it is passed through a line comb filter 3 to remove this. In the line comb filter 3, a subtracter 5 subtracts the current color signal input to the variable delay line 4 from the color signal one line (one horizontal scanning period) before, which is the output of the variable delay line 4.

The variable delay line 4 has a fixed number of delay stages like a shift register, operates by inputting a clock signal, and measures the time from when the first clock is input until the number of clocks becomes equal to the number of delay stages. is the amount of delay. A specific example of the variable delay line 4 is a COD (charge coupled device). Now, if the reference clock frequency of the servo circuit 1 is the value for normal reproduction, the horizontal synchronizing signal period of the reproduced signal and the delay amount of the variable delay line 4 are both normal values (=E33.5μ5ec).

Here, the output frequency of variable frequency oscillator 2 is (1+α)
When doubled, the horizontal synchronization signal period of the reproduced signal is 1/(1+
becomes α). At this time, if the frequency of the clock input to the variable delay line 4 is multiplied by (1+α), the amount of delay will be 1/(1+α).
), and a one-line delay can be performed correctly.

As described above, according to this embodiment, a line comb filter using a variable delay line whose delay amount can be controlled from the outside,
By providing a variable frequency oscillator that supplies a reference clock signal to the servo circuit and a delay amount control signal to the variable delay line, it is possible to play by changing the relative speed, or pitch, between the head and tape while maintaining an on-track state. can do.

Note that only the video signal playback has been explained above;
Regarding audio signal reproduction, when the FM audio signal is recorded with a rotating audio head, the process is exactly the same as when reproducing a video signal. In the case of recording with a fixed head, only the running speed of the tape is affected, so this can also be considered in the above content.

Effects of the Invention As described above, the present invention includes a servo circuit unit that controls the cylinder rotational speed and tape running speed, a line comb filter using a variable delay line whose delay amount can be controlled from the outside, and the servo circuit unit that controls the rotational speed of the cylinder and the running speed of the tape. A variable frequency oscillator for supplying a reference clock signal to a circuit section and a delay amount control signal to the variable delay line, and a control means for controlling the output frequency of the variable frequency oscillator, and controlling the output frequency of the variable frequency oscillator. By changing the output frequency of the variable frequency oscillator, it is possible to perform pitch control playback in which the relative speed between the head and the tape is changed very slightly, which has a great practical effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a video tape recorder according to an embodiment of the present invention, and FIG. 2 is a vector diagram showing the relationship between the moving speed of the head number tape and the trajectory of the head. DESCRIPTION OF SYMBOLS 1... Servo circuit unit, 2... Frequency variable oscillator, 3... Line comb filter, 4... Variable delay line, 5... Subtractor, 6... Volume (control means). Name of agent: Patent attorney Norihei Awano Haka 1 person 3-・-
Line comb filter 7...to mk/y-o-

Claims (2)

[Claims] (1) A servo circuit that controls the rotation speed of the cylinder and the running speed of the tape, a line comb filter using a variable delay line whose delay amount can be controlled from the outside, and a reference clock signal to the servo circuit. , a variable frequency oscillator that supplies delay amount control signals to the variable delay line, and a control means for controlling an output frequency of the variable frequency oscillator, and the output frequency of the variable frequency oscillator is changed by operation of the control means. A videotape recorder that changes the relative speed between the head and tape. 2. The video tape recorder according to claim 1, wherein the line comb filter is used to remove adjacent crosstalk from reproduced color signals.