JPS5948804A - Recording circuit of video tape recorder - Google Patents

Abstract

PURPOSE:To ensure the recording with high performance through a simple constitution of a recording circuit, by recording a mixture signal of a time compressed sound signal and a pilot signal or a mixture signal of a frequency modulated luminance signal and a low band converted chroma signal. CONSTITUTION:A video tape 7 is wound around a rotary cylinder. A time compressed sound signal APCM and a pilot signal P are recorded by video heads 16A and 16B on an oblique track 13 having an about 30 deg. angle of the tape 7. At the same time, a frequency modulated luminance signal YFM, a low band converted chroma signal CL, a frequency modulated sound signal AFM and the signal P are recorded. The record current is controlled by record current setting circuits 32-35. The signal APCM is generated by a processor 36. At the same time, the signals P, YFM and CL are generated by a generator 45, a processor 39 and a processor 42 respectively. As a result, it is possible to attain simultaneously the miniaturization of a tape recorder, the long-time recording and the high sound quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a two-head helical scan type video tape recorder, and more particularly to a recording circuit suitable for time-compressing an audio signal and writing it on an overrun track.

[Prior art]

Conventional video tape recorders record audio signals on dedicated audio tracks, and as the devices become smaller and recording takes longer, the sound quality deteriorates.

had the problem of increasing On the other hand, the outfit.

As a method for achieving both compactness of the device, long recording time, and high sound quality, a method is being considered in which the audio signal is time-compressed and recorded in the video trunk.

In this case, the problem is that the recording circuit becomes complicated.

[Purpose of the invention]

An object of the present invention is to provide a recording circuit which eliminates the drawbacks of the prior art and has a simple configuration and is easy to ensure performance in a device for time-compressing audio encoding and recording it on a part of a video track. It is in.

[Summary of the invention]

In the present invention, the tape is wound around a rotating cylinder at an angle of about 220°, and the time-compressed audio signal and pilot signal are frequency-multiplexed and recorded on a part of the diagonal track formed by the video head (the winding is about 30° angle). Frequency-multiplexed recording of a frequency-modulated luminance signal, a low-frequency converted chroma signal, a pilot signal, and a frequency-modulated audio signal is performed on a diagonal track portion corresponding to an angle of approximately 190°. .

[Embodiments of the invention]

FIG. 1 is a diagram showing an example of the spectrum of a recording signal of a video tape recorder using the present invention. In FIG. 1, 1 indicates an FM carrier of a signal obtained by frequency modulating a luminance signal, 2 indicates an FM lower sideband wave, and 6 indicates an FM upper sideband wave.

4 is a signal obtained by frequency modulating an audio signal, 5 is a signal obtained by converting a chroma signal into a low frequency band, and 6 is a pilot signal.

The pilot signal is a signal used to override the tracking servo during playback, and for example, there is a method of recording carriers of four different frequencies (f1→f2→f3→f4→f1→f2) for each field period of the video signal. An example of frequency is f, -=6.5fh, ft key Z5fh, f3
Ki 10.5 fh, f, Ki 9.5 fh.

(fh: horizontal synchronization frequency).

The spectrum of the time-compressed audio signal should be similar to the spectrum 1.2.3 of the frequency-modulated luminance signal shown in FIG.

- As an example, convert a 2ch audio signal into an 8 to 10 bit l Convert to PCM, compress time to -～-216 is possible.

FIG. 2 is a diagram showing an example of a tape pattern of the present invention. In FIG. 2, 7 is a video tape, 8 is an arrow indicating the running direction of the tape, 9 is an arrow indicating the tracing direction of the video head, 10 is a first optional track provided at the upper end of the tape, and 11 is a tape tape. The second one provided at the bottom end
12 is the first overrun track provided in the leading portion of the diagonal trunk, and 13 is a track on which time-compressed audio signals (hereinafter referred to as APoM) and pilot signals (hereinafter referred to as P) are recorded. , 14 is a frequency-modulated luminance signal (hereinafter referred to as YF
M), a low frequency converted chroma signal (hereinafter referred to as C5), and a frequency modulated audio signal (hereinafter referred to as AFM)
and P are recorded, and 15 is a second overlap track provided in the tray IJing portion of the diagonal track.

FIG. 3 is a block diagram showing an embodiment of the recording circuit of the present invention for forming the tape pattern shown in FIG. 2, and FIG. 4 is a waveform diagram showing waveforms at various parts in FIG.

In FIG. 3, 7 is a video tape, 16A116B is two video heads, 17 is a rotary transformer, 18.
21 is an adder, j9.20, 22, 23 are recording amplifiers, 24.26.28.3o are switches, 25.27.
29.61 is the control terminal of the switch, 62.33.64.
35 is a recording current setting circuit, 56 is a PCM processor that time-compresses the input audio signal and obtains A and CM (G in Figure 3) as output, and 37.38 is a two-channel audio signal (F in Figure 3). 39 is the terminal to which the video signal is inputted, Y
A video processor that outputs an FM signal, 40 a video signal input terminal, 41 a BPF for extracting chroma signals, 42
43 is a color processor to which a chroma signal is input and outputs CL, and 43 is an FM to which an audio signal is input and outputs AFM.
44 is an audio signal input terminal; 45 is a pilot generator that generates a pilot signal (P) shown in FIG. 3J; and 46 is an adder that mixes CL, AFM, and P.

In FIG. 4, A is a rotating video head 16A116B.
B is a vertical synchronization signal of the video signal to be recorded, C is a signal with a frequency six times that of A and whose phase is synchronized with A, D is a pulse made from C, and switch 24 .28 control. E is the pulse made from C and controls switch 26.30. F is a 2-channel audio signal, and G is APcM which is time-compressed F.
It's a signal. As shown in the figure, the signal of period F is converted to G and F2 is converted to 02.

H1, K, and L indicate the output signals of recording amplifier 19.22.20.2. The letters in the figure indicate the spatial arrangement of the diagonal tracks in FIG. The shaded area indicates the period during which the video head does not trace the tape.

J indicates the output signal of the pilot generator 45, which has a frequency f at the field period of the video signal.

→ changes from f2 → f3 → f4 → f1.

Video head i6A begins to form track 14a of FIG. 2; when head 16B is not tracing the tape,
Switches 24, 26, 28, 60 are all connected to the V side. High to switch control terminal 25.27.29.31
When the h voltage is applied, the switch is connected to the A side, and the Lo
When w voltage is applied, the switch is connected to the V side.

Therefore, head 16A forms 14a and head 1
During the period when 6B does not trace the tape, both H1 and ■ become the output signal YFM of the video processor 39, and both ■( and L are the output signals of the adder 46, CL+AFM+P(
f2). Therefore, 142 tracks include YFM.
+ CL + AFM + P (f2) is recorded.

Next, a period during which the head 16B traces the track 12b will be explained. During this period, the head 16A traces the track 14a, and switches 24, 26, 28
．． 30 are all connected to the V side, and the signals H, I, K, and L are the same as above. Therefore, trunks 12b, 14a
YFM+CL+AFM+P (f2) is recorded in .

Next, the period during which the head 16B forms the track 13b will be explained. During this period, the pulse E becomes a high voltage, and the pulse D becomes a low voltage. Therefore switch 2
4.28 is connected to the V side, switch 26.30 is connected to the N side, the H signal is YFM, the I signal is A, and so on. M (G
2), the K signal becomes CL+AFM+P(f2). Therefore, the 13b track has APCM (G2) +
P (f 2), but 14a track has YFM+CL+
AFM+P(f2) are recorded respectively.

Next, the period during which the 16A head forms the 15a track will be explained. During this period, pulses D and E are both LOW, and switches 24, 26, 28, and 30 are all connected to the V side. Therefore, tracks 15a14b have YFM
+ CL + AFM + P (f s) is recorded.

Next, a period in which the 16A head does not trace the tape and the 16B head forms a 14b track will be described.

During this period, all the switches 24, 26, 28, and 30 are connected to the V side. Therefore, the 14b track has YFM.
+ CL + AFM + P (f s) is recorded.

Next, the period during which the 16A head forms 120 tracks will be explained. During this period, switches 24, 26, 28.
30 are all connected to the V side. Therefore, the 12C114b track requires YFM + C.
7° in which L + AFM + P (f s) is recorded.Next, the period during which the 16A head forms the 16c track will be explained. During this period, pulse D is HIGH and pulse E is LOW. Therefore, switch 24.28
is connected to the A side, and switch 26.60 is connected to the V side. Therefore, the 13C track has APCM (G
s) + P Cf5) is recorded, and YFM + CL + AFM + P (f s) is recorded on the 14b track.

Similarly, YFM +CL + AFM + P (f+) is recorded on the 14C, 15b, 12d) racks, APCM (G4) 10P (f4) is recorded on the 13d track, and 15c, 14d, 12e.
, YFM+CL+AFM+P(f+) on the track
However, the 13e track has APCM ((3s) +P(
, fl) are recorded, respectively.

Next, the features of the circuit configuration shown in FIG. 3 will be explained.

In FIG. 3, there are four recording current setting circuits 32.3'! I, 3
By providing 4.35 in the position shown in the figure, it is possible to minimize the number of adjustment circuits and to optimize the YFM, A, and CM recording currents. Normally, the recording currents for Y FM and APCM are chosen to be approximately equal. However, the recording current of YFM also serves as a bias for CL and AFM, and it may be desirable to select YFM at a value 1 to 2 dB larger than the optimum recording current.

By adjusting the current setting circuit 32, the head 16A, 1p
The APoM current flowing to B can be set at the same time.

By adjusting the circuit 63, the YFM currents flowing through the heads 16A and 16B can be set simultaneously.

Since the CL and AFM1P signals are recorded using YFM or APcM as a bias, the optimum mixing ratio should be changed not only according to the values shown in FIG. 1 but also according to the characteristics of the head used. Normally, the characteristics of individual heads are measured, the heads are classified into ranks, and after the heads are assembled into a system, the mixing ratio is changed according to the ranks.

Taking this situation into consideration, FIG. 3 shows an example of a rational mixing ratio setting circuit. In FIG. 6, the CL, AFM, and P signals are added at a constant level and then adjusted by one recording current setting circuit 34. By adjusting the circuit 34, the heads 16N, 1
CL s AFM's P for YFM flowing to 6B
The mixing ratio of can be set at the same time.

A circuit 65 is a mixing ratio setting circuit for APcM and a P signal recorded as a bias, and sets the current flowing to both heads 16A and 1613 at the same time.

In FIG. 3, the circuit is simplified by allowing signal current to flow through the heads 16A and 16B even in the hatched areas H, I, K, and L in FIG. 4. Similarly, tracks 12a, '12b, 12
The circuit is simplified by recording the above-mentioned signals in c, . . . as well.

Also, in Figure 6, there are four switches (24, 26, 28, 3
0) is designed to simplify the configuration of the recording amplifier.

FIG. 5 is a circuit diagram showing one embodiment of the recording amplifiers 19, 20 and adder 18 in FIG.

47 in FIG. 5 corresponds to 18.19.20 in FIG. The transistor Q1 constitutes a recording amplifier 19, and the transistor Q2 constitutes a recording amplifier 20. In Figure 5, the transistor Q1 that flows a large current of about 20 mApp and the transistor Q2 that flows a small current of about 4 mApp are separate, and cross modulation in the circuit does not become a problem, so the idle current of Ql can be reduced by /JS. .

In addition, by providing Ll, it is easy to secure a large dynamic range, use low Vcc, and facilitate power-saving design.
It has the advantage that it is easy to flatten the frequency characteristics of the recording current.

FIG. 6 is a block diagram showing another embodiment of the recording circuit of the present invention for forming the tape pattern of FIG.

In FIG. 6, 48 is an adder for mixing APCM and P signals, 49 is an adder for mixing YFM and CL+AFM+P signals, 50 is a switch, and the waveform shown in FIG. 4 is applied to the control terminal 51. When D is High, it is connected to the A side, and when D is Low, it is connected to the V side.

Reference numeral 52 denotes a switch, and the waveform shown in FIG.
is connected to the V side during the period when is Low.

54 and 55 are recording amplifiers, respectively.

The feature of FIG. 6 is that only two switches and two recording amplifiers are required. The setting characteristics of the recording current are almost the same as those shown in FIG.

An embodiment of the recording amplifier 54 used in FIG. 6 is shown in FIG. Recording amplifier 540 input signals are YFM and CL+AFM
+P mixed signal, and cross-modulation in the recording amplifier poses a problem. Therefore, it is necessary to use a push-pull type amplifier as shown in FIG. In this case, the amplifier 54 drives the head 16A with a constant voltage, and the frequency characteristic of the recording current becomes a high-frequency attenuation type. Therefore, in order to flatten the frequency characteristics of the recording current, the high frequency compensation circuit 56 is required.

FIG. 8 is a block diagram showing another embodiment of the recording circuit of the present invention for forming the tape pattern of FIG. 2.

The feature of the circuit configuration in FIG. 8 is the recording current setting circuit 57.5.
8.59.60 is provided after the switch 24.26.28.30.

With such a configuration, the head 16A.

1 (SB recording current setting can be done independently.

〔Effect of the invention〕

According to the present invention, it is possible to simultaneously achieve miniaturization of a video tape recorder, long-time recording, and high sound quality, and the recording circuit required for this can be simplified.

[Brief explanation of drawings]

FIG. 1 is a spectrum diagram showing an embodiment of the recorded signal spectrum of the video tape recorder of the present invention, FIG. 2 is a block diagram showing an embodiment of the video tape recorder path of the present invention, and FIG. 5 is a circuit diagram showing an embodiment of the recording amplifier used in FIG. 6,
6 and 8 are block diagrams showing another embodiment of the recording circuit of the video tape recorder 7 of the present invention, and FIG. 7 is a circuit diagram showing an embodiment of the recording amplifier used in FIG. be. [Explanation of symbols] 7... Video tape, 16A116B... Video head, 66... PCM processor, 3'... Video processor, 42... Color processor, 45... Pilot signal generator. E Patent applicant name (510) Stock company God
(b) Standing production agent
Drawings subject to human correction (3 drawings).

Claims (1)

[Claims] In a two-helical force scan type video tape recorder, the rotating cylinder has an angle of about 220 degrees ff. A device for winding a video tape, two video heads, a device for converting an audio signal into a time-compressed signal, a device for generating a pilot signal, and a device for generating a frequency-modulated luminance signal. It has at least a device that generates a chroma signal whose frequency is converted to a low frequency range, and the current flowing through the video head in the recording state is a mixture of at least the time compressed signal and the pilot signal, or at least the frequency modulated luminance signal. A recording circuit for a video tape recorder, characterized in that a low frequency converted chroma signal and a pilot signal are mixed.