JPS6262456A - Recording speed discriminating device for video tape recorder - Google Patents

Abstract

PURPOSE:To fix a noise bar and to discriminate a recording speed during a high speed reproducing by discriminating the recording speed based on a level difference of two types of difference frequencies produced by a multiplication of a reproducing pilot signal and a reference signal in a specific block. CONSTITUTION:A signal sample held in a sample holding circuit 10 by a timing signal is inputted to a recording speed discriminating logic circuit 13 which is waveform shaped in a Schmidt circuit 12. When a tracking is performed, an output of the Schmidt circuit 12 remains to be H and when a reproducing speed is different from a recording speed, the output of the Schmidt circuit 12 repeats 'H', 'L'. Accordingly, the reproducing speed discriminating logic circuit 13 discriminates this and outputs an instruction for changing a recording speed mode during the repetition of 'H', 'L'. Thereby, during a high speed reproducing, while a noise bar on a screen is fixed, the recording speed can be discriminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a recording speed determination device for a video tape recorder (v'rR), and more particularly to a recording speed determination device during high-speed playback.

[Technical background of the invention]

The so-called 8 wealth! In an 1VTR, a now tracking method is employed in which a pilot signal whose frequency changes cyclically for each track is superimposed on an information signal and recorded on a tape, and tracking is performed based on this pilot signal during playback. Several proposals have already been made on how to fix the noise bar that is generated by crossing tracks during high-speed playback, such as fast-forward playback and rewind playback, at a predetermined position on the screen in such a VTR. A method has been considered in which the signal is multiplied by a pilot signal reproduced from an adjacent track to create two types of difference frequency signals, and the scanning locus of the head relative to the track is fixed by performing tracking control as in normal reproduction.

On the other hand, a method is also known in which the recording speed of a tape is automatically determined during normal playback.However, there is no example in which the recording speed is determined when the noise bar is fixed (during high-speed playback) as described above.

[Problems with background technology]

If parts with different recording speeds are played back at different speeds during high-speed playback, a phenomenon occurs in which the noise bar is not fixed and moves, making it difficult to see on one screen.

Therefore, it is desirable to perform recording speed determination even during high-speed reproduction. However, in the above-mentioned noise bar fixing method using the reference signal switching method, it is difficult to achieve both noise bar fixing and recording speed discrimination.

[Purpose of the invention]

The present invention has been made in view of the above points, and an object of the present invention is to provide a recording speed discrimination device that can achieve both stability of tracking control and stability of recording speed discrimination during high-speed reproduction.

[Summary of the invention]

The present invention supplies a reference signal corresponding to the recorded pilot signal to a specific section on the video head scanning trajectory during high-speed playback in a different order from the order of the reference signals for fixing the noise bar. The recording speed is determined based on the level difference between two types of difference frequency signals generated by multiplying the reproduced pilot signal and the reference signal.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a recording speed determination device for a video tape recorder according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the invention.

(1) is an input terminal into which a reproduction signal from a magnetic head (not shown) is input, and (2) is a bandpass filter (BPF).
).

(3) is the balanced modulator (BM), (4) is the frequency fH (
fH is the horizontal synchronization frequency) BPF, (5) is the frequency 3
fH BPF, (6) and (7) are detectors, (8) is a differential amplifier, (9) and (11 are sample and hold circuits. Also, aυ is a capstan servo signal output terminal,
(1 is the output terminal of the simulator circuit, Q3 is the recording speed discrimination logic circuit, and the U similarity discrimination output.

Further, (19 is a head switching pulse input terminal, (tte) is a clock signal input terminal, (17) is a reference signal generation circuit, and (17) is a timing signal generation circuit.

Next, the operation of the above-described apparatus during high-speed reproduction will be explained with reference to FIG. 2, which shows the scanning locus of the head, and FIG. 3, which is a timing chart. First, for convenience of explanation, the operation of fixing the noise bar during high-speed reproduction will be described, and then the operation of determining the recording speed will be described. FIG. 2 shows head scanning trajectories (HT person, HTB) during 5x speed playback. A1. B...
A, Bt... indicate tracks recorded by the A head and the B head, and these tracks have four types of low frequency pilots of the same wave number that are not affected by the azimuth loss effect and are superimposed on the information signal. Signal (frequency f1=6
．． 5fH.

f, = 7.5fH1f, = 10.5fH1f number = 9.5
fH) are recorded cyclically for each track. Here, when the head mainly scans the track A, the section is divided into sections T, and when the head mainly scans the track B, the section is divided into sections Tt.

Then, when scanning the track A1 on which the pilot signal of frequency f is recorded, the reference signal generating circuit αD
A reference signal of frequency f is generated from . Therefore, the pilot signal (frequency 't) reproduced in the part marked O in one section T8 is multiplied by BM (3I,
A signal component of frequency rH corresponding to this is output from M(3). In addition, the frequency f4 is used as a reference signal in the T3 interval.
When a reference signal of T is supplied, one section T! The pilot signal (frequency ts) reproduced from the part marked with an x is BM
(3) Multiplied by t, BM (3j outputs a signal component with a corresponding frequency of 3fH. Similarly, the recording pilot signal of the scanning track (scanning section) (see Fig. 3 (a) ) according to the reference signal in Fig. 3 (b
)! When generated as shown, a frequency fH acid component difference frequency signal is obtained from BM (3!) corresponding to the part marked with ○ in FIG.
A difference frequency signal of frequency 3fH component is obtained from M (3). These difference frequency signals are respectively BPF(4), (
5) and detected by a detector (6).

Then, the differential amplifier (8) compares the force outputs of both transverse wave generators 16), and the comparison error is applied to the capstan motor drive circuit (not shown) via the output terminal Uυ. Feedback is applied to the motor, and the head scans a fixed trajectory so that the amplitude levels of the two difference frequency signals are equal.Therefore, the noise bar caused by crossing the track always appears at a fixed position on the screen. It will be (fixed).

The frequency of the signal recorded on the track scanned by the human head is G+'t*tf4e'l.

B head is 't+ fme '4+ flo'! (Furthermore, at the next person's head, r '4 * fl + f
lo '3) Therefore, the order in which the reference signals are generated needs to match the order in which the pilot signals are generated.

Figures 3(C) and 3(d) show the output waveforms of the difference frequency signals of frequencies fH and 3fH, respectively. Also, Figure 3(e)
shows the output waveform of 3fH-fH. In addition, each section T
.

For T to T, the reference is T/1n-11, where T is the entire section (n is the speed number). For example, in 5x fast forward playback, the reference period of each section is 7x, and in 5x fast forward playback, it is -. In the example, T, ,T depends on the position of the noise bar.
, has changed, but TI + TI1 has become .

Next, the recording speed determination operation of this embodiment will be described. In the above description of the tracking operation, it has been explained that the reference signals are supplied in a predetermined order, but in reality, the order of the reference signals supplied is changed midway through, as will be described later, in relation to the recording speed determination operation.

In the first embodiment, the section T is used to determine the recording speed. That is, tracking for fixing the noise bar is performed in intervals T,, T,, T,, T, and one interval T2
is excluded (in this section T, the previous value is held and tracking control is performed using this value). The reference signal given to section T2 (the shaded part (see Figure 2)) is, for example,
The difference frequency signal is fH (or 3fH), and in this case, 't, 't, f4+ 's (or f4
+G+f2+'t) respectively. If you look at it all together.

Reference signal generation circuit (1η is when the frequency is f1+G+
and others.

't+ f1+ f4* '4* 't* flt'
Reference signals are generated in the order of 4'' (see Figure 4 (a)).
The obtained differential homogeneous output signals are shown in Fig. 4 (b), (C),
(d). The timing of sample and hold for tracking in section T2 is given to the sample and hold circuit (9) from the timing signal generating circuit ttS (see Figure 4(e)), and the waveform of the output terminal αυ is as shown in Figure 4). It becomes like this. In addition, the timing of sample and hold for determining the recording speed is best at the time when the signal level of the frequency fH is the highest, and similarly, the timing signal generation time wr
The signal is given to the sample and hold circuit (9) as shown in FIG. 4 (9).

The signal sampled and held in the sample-and-hold circuit (101) by the timing signal as described above (see FIG. 4 (h)) is then input to the recording speed discrimination logic circuit (13) whose waveform is shaped in the Schmitt circuit (2). be done.

Schmitt circuit α when tracking is performed
The output of the Schmitt circuit α2 remains rHJ, and if the playback speed is different from the recording speed, the output of the Schmitt circuit α2 remains rHJ, r
Repeat LJ. Therefore, this is determined by the recording speed discrimination logic circuit (13H), and when rHJ and rLJ are repeated, an instruction is issued to change the reproduction speed mode.

Note that the head switching pulse is shown in FIG. 4(i). As described above, recording speed can be determined while keeping the noise bar on the screen fixed even during high-speed playback.

Note that in this embodiment, the recording speed was determined only in section T, but in this case, the recording speed was determined in multiple sections (for example, T2 and T.

This can also be done by looking at the level difference of the difference frequency signal in the interval ). Regarding the timing of determination, even if the multiple speed number is the same, the intervals at both ends of the head scan (T in the embodiment).

and T1 section) change in length (the sum is constant), so for example, if the second track is used for discrimination.

TI+! It is sufficient to perform speed discrimination at this point.

〔Effect of the invention〕

As described above, according to the present invention, noise bar identification and recording speed determination can be performed even during high-speed reproduction.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a recording speed determination device for a video tape recorder according to the present invention. FIG. 2 is a diagram showing the head trajectory during high-speed reproduction. FIG. 3 is a timing chart of the apparatus of FIG. 1 when only tracking is performed, and FIG. 4 is a timing chart of the apparatus shown in FIG. 1d when both tracking and recording speed determination are performed. 3... Multiplier, 4.5... BPF. 6.7...Detector, 8...Differential amplifier. 10...Sample hold circuit, 12...Schmitt circuit. 13.-- Speed discrimination logic circuit. 17...Reference signal generation circuit. 18...Timing signal generation circuit. Agent Patent Attorney Noriyuki Chika Yudo Hiroshi Uji Figure 1 Figure 2

Claims (1)

[Claims] In a recording speed determination device for a video tape recorder, which records pilot signals of four different frequencies on a magnetic head cyclically for each track and records them on a tape together with an information signal, and performs tracking control based on the pilot signals during playback. , cyclically supplying reference signals having four types of frequencies equal to the frequency of the pilot signal one after another as the magnetic head traverses the track during high-speed reproduction, and In the track section, means for supplying a reference signal different from the reference signals in the supply order, a multiplier for combining the reference signal and the reproduced pilot signal, and levels of two types of difference frequency signals obtained from the multiplier. 1. A recording speed determination device for a video tape recorder, comprising: means for determining a difference; and determining means for determining a recording speed based on the output of said means for the predetermined track section.