JP2649917B2 - Rotating head playback device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary head type reproducing apparatus, and more particularly to a rotary head type reproducing apparatus having a circuit for correcting a time axis of a reproduced signal.

2. Description of the Related Art Conventionally, a time axis correction circuit (time base corrector TBC) in a device of this type, for example, a video tape recorder (VTR) using a well-known low-pass conversion method, converts a horizontal synchronization signal extracted from a reproduced video signal into a signal. The frequency of the low-frequency conversion carrier color signal frequency is multiplied by a PLL circuit, and this signal is converted to a voltage controlled oscillator (VCO) output signal that is controlled based on the phase difference between the reference oscillator and the reproduced color burst signal. The low-frequency converted carrier color signal reproduced by the signal is frequency-converted to obtain a time-corrected carrier color signal.

As a method of correcting not only the carrier chrominance signal but also the time axis of the luminance signal at the same time, the reproduced video signal is
It is also considered to supply a variable delay line composed of a delay line, extract a time-axis variation using the horizontal synchronization signal, and control the delay time by the variable delay line to perform time-axis correction.

[Means for Solving the Problems] In the conventional TBC, the most effective effect is obtained at the time of normal reproduction. Therefore, the so-called special reproduction, in which the conveyance speed of the recording medium and the rotation speed of the rotary head are different from those at the time of recording. Sometimes, a sufficient effect cannot be obtained. This is because the time axis fluctuation amount differs between the normal reproduction and the special reproduction.
That is, the amount of time axis fluctuation during special reproduction is large, and skew and jitter exceeding the TBC correction range during normal reproduction are generated. For this reason, TBC is generally not used or cannot be used during special playback, and the range of use of TBC has been narrow. Also, providing a TBC dedicated to special reproduction has a disadvantage that the circuit becomes large.

The present invention has been made in order to solve the conventional problems as described above, and it is possible to obtain a sufficient time axis correction effect in any case simply by providing some additional circuits in a normal TBC circuit. It is an object of the present invention to provide a possible playback device.

[Means for Solving the Problems] In order to achieve the above object, a rotating head type reproducing apparatus according to the present invention provides an image recorded on a recording medium by tracing the recording medium with the rotating head. An apparatus for reproducing a signal, comprising: delay means for delaying a reproduced video signal output from the head; extracting a synchronizing signal in the reproduced video signal and comparing the phase with a predetermined reference signal to obtain a time axis error. A time axis error detecting means for detecting a signal, and a time axis correcting means for correcting a time axis by varying a delay time of the delay means based on the time axis error signal detected by the time axis error detecting means. And, according to the transport speed of the recording medium during reproduction,
And a control means for changing a frequency response characteristic of the time axis correction means.

[Operation] With the above configuration, the time axis correction can be performed automatically by following the magnitude of the time axis fluctuation only by providing a simple additional circuit, so that sufficient time axis correction can be performed in any case. Can be.

[Embodiment] An embodiment in which the playback apparatus of the present invention is applied to a VTR will be described below.

FIG. 1 is a block diagram schematically showing a main part of a VTR according to one embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a charge-coupled device (CC) supplied with a reproduced video signal reproduced from a magnetic tape T by a rotary head H and used as a variable delay element.
D), 2 is a sync separation circuit for extracting a horizontal sync signal from the video signal output from the CCD 1, 3 is a phase comparator, and the output of the phase comparator 3 is voltage controlled through a low-pass filter (LPF) 4. The phase of the reproduced horizontal synchronization signal supplied to the oscillator (VCO) 5 is compared with the oscillation frequency of the VCO 5 and separated by the synchronization separation circuit 2. The output of the phase comparator 3 is supplied to the VCO 7 via the equalizer 6, and the frequency of the VCO 7 becomes the clock of the CCD1. And this phase comparator
3, PLL is composed of LPF4 and VCO5. Reference numeral 8 denotes a system controller for switching the VTR between various modes such as normal reproduction, still image reproduction, slow motion reproduction, and high-speed search reproduction, and 9 denotes a magnetic tape T at a speed determined based on the mode designated by the system controller 8. This is a capstan for transporting Reference numeral 10 denotes a reproduction signal processing circuit for performing well-known signal processing on the video signal whose time axis has been corrected by the CCD 1 and returning the signal to the original state, and reference numeral 11 denotes a video signal output terminal.

In the VTR shown in FIG. 1, at the time of normal reproduction, the capstan 9 is used to convey the magnetic tape T at the same speed as at the time of recording. The horizontal synchronizing signal is extracted, and the extracted horizontal synchronizing signal becomes one input of the phase comparator 3. The output of the phase comparator 3 changes the input voltage of the VCO 5 via the LPF 4 to change the frequency of the VCO 5. The oscillation output of the VCO 5 and the reproduced horizontal synchronization signal are compared in phase by the phase comparator 3 and output as a time axis error signal. This time axis error signal is also phase-compensated by the equalizer 6 and supplied to the VCO 7,
The oscillation frequency of the VCO 7 is changed, the CCD 1 is driven using the output of the VCO 7 as a clock, and the time axis of the reproduced video signal is corrected by changing the delay time of the CCD 1.

Next, at the time of special reproduction, for example, when high-speed search reproduction of a recorded portion is performed, the system controller 8 operates the capstan 9 to fast-forward the tape T and outputs a signal S indicating that the tape is in a search state. While the search signal S is being output, the response speed of the VCO 5 is changed by changing the time constant (or gain) of the LPF 4, and the time axis error signal at the time of the high-speed search is output from the phase comparator 3 and the overall response is obtained. The characteristics are changed, and the time axis is corrected by the same operation as in the normal reproduction.

In the above-described embodiment, the time constant (or gain) of the LPF 4 is changed at the time of special reproduction. However, it is also possible to adjust the time constant (or the gain) by the equalizer 6 in addition to this method. What is necessary is just to change the frequency of the VCO 7 by changing the voltage, and which means is used can be selected according to the case. In the embodiment, the high-speed search reproduction is taken, but not limited to the search.
For example, the present invention is similarly applicable to slow reproduction, still reproduction, and the like. That is, the response characteristic of the time axis correction circuit is appropriately switched by switching the time constant of the LPF 4 and the characteristics of the equalizer 6 according to the magnitude of jitter, skew, and the like generated during slow reproduction and still reproduction. By performing the time axis correction at a response speed that is optimal to the above, excellent time axis correction can be performed in any mode. In this case, the system controller 8 outputs a signal S corresponding to each mode.

[Effects of the Invention] As described above, the rotary head type reproducing apparatus according to the present invention only needs to add a small number of circuits to the TBC circuit at the time of normal reproduction, and in any case, can reproduce the reproduced video signal reproduced from the head. And good time axis correction can be performed.

[Brief description of the drawings]

FIG. 1 shows a TBC in a reproducing apparatus according to an embodiment of the present invention.
FIG. 3 is a block diagram schematically showing a main part of FIG. In the figure. 1: CCD, 2: Sync separation circuit 3: Phase comparator, 4: LPF 5, 7: VCO, 6: Equalizer

Claims (1)

(57) [Claims] An apparatus for reproducing a video signal recorded on a recording medium by tracing the recording medium with a rotating head, a delay unit for delaying a reproduced video signal output from the head, A time axis error detecting means for detecting a time axis error signal by extracting a synchronization signal in the reproduced video signal and comparing the phase with a predetermined reference signal; and the time axis error detected by the time axis error detecting means. A time axis correcting means for correcting a time axis by changing a delay time of the delay means based on a signal; and a frequency response characteristic of the time axis correcting means according to a transport speed of the recording medium during reproduction. A rotating head type reproducing apparatus comprising: a control unit for changing the rotational head type.