JPS6310984A - Rotating head type video signal reproducing device - Google Patents

Abstract

PURPOSE:To obtain a good reproducing picture at various reproducing speeds by making the running speed of a tape shape recording medium about 1/2(2m+1) times the speed at the time of recording, and updating data in a field memory only when a signal level reproduced from a main reproducing track is above a prescribed value. CONSTITUTION:A capstanc control circuit 16 runs a magnetic tape at the speed 1/2(2m+1) times the speed at the time of recording. A writing to the field mem ory 4 is carried out by the clock of a clock generator 9 and a writing period is limited to a period when an envelope detecting level detected by the envelope detector 13 of a reproducing RF signal is above a constant value. Namely, a period when the envelope detecting level of the RF signal exceeds a threshold is detected and the data of the field memory 4 is updated only during the period when the output of a gate pulse generator 14 generated thereby goes to 'H' (high). Thereby, all the data in the memory can be updated with the comparative ly reduced number of traces, so that the good reproducing picture can be obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention is a rotating head type video signal reproducing device.

In particular, the present invention relates to a rotary window type video signal reproducing apparatus having a memory capable of storing one screen's worth of video signals.

[Prior Art] Conventionally, in video tape recorders (VTRs),
When performing so-called high-speed search playback, the position of the noise bar on the screen is fixed to make the reproduced image at the time of high-speed search playback as easy to view as possible.

Figures 3 and 4 are diagrams showing the trace trajectories of a tape and a head as a recording medium during high-speed search playback in a conventional VTR that performs tracking control using a four-frequency system.In Figure 1, fl+f2+... is a tape shows the pilot signal recorded in.

A,, B,,... (however, i = integer of 1, 2...)
shows the trace trajectories of both heads A and B with different azimuth angles.

(i) When performing high-speed search playback at a tape running speed (4 m + 1) times that of recording, Figure 3 (a) shows the trace locus of the rotating head on the tape when m = 1. Middle f.

f , , f , , f indicate the frequencies of pilot signals recorded in a superimposed manner on each track. FIG. 5B shows the frequency of the local pilot signal multiplied by the reproduced pilot signal in the four-frequency trawl control circuit.

As is well known, when obtaining a tracking error signal using a four-frequency method, the frequency f A (=
f x - f + = f x - f 4) Component and fa
(=f4-f1=fs fz) components to obtain the tracking error signal (ATF signal)?
This indicates a tracking error for a track where a pilot signal with the same frequency as the local pilot signal is recorded. Therefore, the tape running speed at the time of recording is (4).
In the case of m + 1) times, the control target track appears for every (4m + 1)) rack, so the frequency of the local pilot signal becomes f1 → f2 → f2' = every trace of the rotating head.
A tracking control signal for fixing the position of the noise bar is obtained by switching at a rotation of f4 and sample-holding the ATF signal thus obtained at a predetermined phase of the rotary head.

Note that FIG. 3 shows a trace locus when the ATF signal is sampled and held at the timing immediately after the rotary head enters the magnetic tape.

(ii) When performing high-speed search playback at a tape running speed (4 m + 1) times that of recording, Figure 4 shows a trace trajectory as shown in Figure 4 (a) when m = 1; (b) shows the frequency of the local pilot signal. In this case, the frequency of the local pilot signal is f1→f4−? Let f yu → f, and similarly A
The noise bar can be fixed by sampling and holding the TF signal at a predetermined rotational phase of the rotary head. FIG. 4 shows an example in which the ATF signal is sampled and held at the timing immediately after it enters the rotary head or the tape.

[Problems to be Solved by the Invention] Although the conventional method described above can fix the position of the noise bar in the reproduced image, the occurrence of the unsightly noise bar itself is unavoidable.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a rotating head type video signal reproducing device that has a simple configuration and can obtain good reproduced images at various recording medium running speeds. With the goal.

[Means for Solving the Problems] In the rotary head type video signal reproducing device according to the present invention, the running speed of the tape-shaped recording medium at the time of recording is approximately q(2
m + 1) times, and only when the level of the signal reproduced from the main reproduction track is above a predetermined value, the data in the memory that stores the video signal for one screen with the video signal reproduced by the rotary head is updated. It is structured as follows.

[Operation] By configuring as described above, all the data in the memory can be updated with a relatively small number of tracings, so that a good reproduced image can be obtained. It is also possible to make detailed speed settings.

[Embodiment] FIG. 1(a) is a block diagram showing the main part configuration of a two-head helical scan type VTR as an embodiment of the present invention, and FIG. A timing chart for explaining the operation of the VTR is shown, and 30PG in (i) is a signal of 30H2 synchronized with the rotation of the rotating drum. In FIG. 1, 2 is a low-pass filter (LPF) to which the reproduced video signal input to terminal l is supplied;
3 is an analog-digital (A/D) converter, 4 is a field memory, 5 is a digital-analog (D/A) converter, 6 is a low-pass filter (LPF), 8 is a synchronization signal separation circuit, 9 is a clock generator 10 is an address control circuit, 11 is a reference clock generator, 13 is an envelope detector, 14 is a gate pulse generator, 15 is a system controller, and 16 is a capstan control circuit.

Now, when a video signal is input from the terminal l, the band is limited by the LPF 2 and the synchronizing signal is separated by the synchronizing signal separation circuit 8. Also, the signal that has passed through LPF2 is A,
In the A/D converter 3, the synchronizing signal is A/D converted using a clock generated by the clock generator 9, written to the field memory 4 at a timing described later, read out, and inputted to the D/A converter 5. , reference clock generator 1
D/A conversion is performed using the reference clock from 1, and LPF6
It is output after passing through.

The operation of high-speed search playback in this VTR will be described below.

When high-speed search playback is commanded by the system controller 15, the capstan control circuit 16 controls the 34 (
A magnetic tape (not shown) is run at a speed of 2m+1) times, and the writing of data to the field memory 4 is controlled using the output of the gate pulse generator 14, as will be described later.

The writing and reading operations to and from the field memory 4 will be explained below.

Writing to the field memory 4 is performed by the clock of the clock generator 9, but during the write-in period, the reproduction R
This is limited to when the envelope detection level detected in envelope detection $13 of the F signal is equal to or higher than a certain value. That is, detecting a period in which the RF row signal envelope detection level exceeds a certain threshold as in the first (3(b)(ii)),
The output of the gate pulse generator 14 generated thereby (
The data in the field memory 4 is updated only during the period when (b) (ii) in FIG. 1 is "H" (high). The address of this updated data is determined by the address control circuit 9 based on the timing from the vertical synchronization signal and the like. The data written into the field memory 4 at the aforementioned timing is read out using the reference clock from the reference clock generator 11.

Figure i2 shows the approximate length (2m+1) in the VTR of this example.
FIG. 4 is a diagram for explaining how data in a field memory is updated during double-speed search playback, taking m=4 as an example.

In Fig. 2, A + and B I are A with different azimuth angles,
This figure shows the envelope waveform of the reproduced signal for one trace of the BPf head, that is, for one field.

According to FIG. 2, the reproduced signal in the shaded portion becomes the data for data updating in the field memory. As mentioned above, in the case of azimuth overwriting in a VTR, all data in the field memory is updated in four fields (four traces).

Although the above embodiment has been described by taking as an example a two-head helical scan type VTR that performs azimuth overlapping reading, the present invention can be applied regardless of the head configuration and the presence or absence of an azimuth angle. That is, by setting the threshold level of the gate pulse generator 14 low in a VTR having a guard band in which azimuth recording is not performed, all data in the field memory can be updated in two traces (two fields). This allows for good high-speed search playback.

[Effects of the Invention] As explained above, the present invention increases the running speed of the tape-shaped recording medium by about 3A (2m+1) times the recording speed, and only when the signal level reproduced from the main reproduction track is higher than a predetermined value, the field By using a configuration that updates data in the memory, good reproduction images can be obtained at various reproduction speeds.

[Brief explanation of drawings]

FIG. 1(a) is a block diagram showing the main structure of a VTR as an embodiment of the present invention, and FIG.
Figure 2 is a timing chart for explaining the operation of the VTR shown in Figure 2. Figure 2 is a diagram for explaining how data in the field memory is updated at a tape speed approximately 4.5 times that of recording. This figure shows the trace locus of a head on a tape during high-speed search playback in a conventional VTR. In the figure. 3. A/D converter 4. Field memory 5: D/A
Converter 6 LPFs 8: Synchronous signal separation circuit 9, clock generation circuit 10, address control circuit 11, reference clock generator 13: envelope detector 11: gate pulse generator agent On patent attorney 1) Haru Kitatake (LLl< Mountain

Claims (1)

[Claims] A device for reproducing video signals recorded field by field on a large number of diagonal tracks formed in parallel on a tape-shaped recording medium using a rotary head, comprising a memory capable of storing one screen worth of video signals, The running speed of the tape-shaped recording medium is approximately 1/2 (2m + 1) times the recording speed (however, m
= an integer of 1, 2, 3...), and the data in the memory is updated with the video signal reproduced by the rotary head only when the signal level reproduced from the main reproduction track is equal to or higher than a predetermined value. A rotating head type video signal reproducing device characterized by: