JPS6057274B2 - Color video signal recording and reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color video signal recording and reproducing apparatus capable of recording and reproducing both PAL and SECAM type signals.

When trying to record and play back both P-Kawaichi and SECAM signals using the same signal processing system as much as possible in a simple VTR, in order to obtain good image quality, it is necessary to distinguish between the two signals so that some Signal processing must be performed separately.

Therefore, if a malfunction occurs in the PAL and SECAM color signal discrimination circuits, or in other words, the PAL color killer detection circuit and the SECAM color killer detection circuit, the reproduced image quality will deteriorate because the signal processing is different. Similar to PAL color television receivers, simple VTRs generally use the N°C color killer detection method to detect PAL color states, and with this, there are no malfunctions caused by SECAM color signals.

However, the detection of SECAM color status is different from that of SECAM color television receivers (hereinafter referred to as SECAM television), and the following method is usually adopted. Its basic circuit diagram is shown in FIG. 1 is a color signal input terminal, 2 is a burst gate pulse input terminal, 3 is a color killer voltage output terminal, and CF is a 4.5N for audio signal commonly used in television receivers.
It is a 4H2 ceramic filter.

Hereinafter, regarding the SECAM color signal as well, similar to the PAL color signal, the color signal that is several μsec after the horizontal synchronization signal will be tentatively referred to as a burst signal. Only the burst portion of the color signal input to terminal 1 is extracted by the positive burst gate pulse supplied to terminal 2, and the burst signal is amplified and output to the collector of NPN transistor Q1 as shown in Figure 2a. Ru. Then, when this signal is passed through a ceramic filter CF, its frequency characteristics change the SECA
At M, the signal becomes a burst signal having a level difference every horizontal period (hereinafter referred to as IH) as shown in FIG. Therefore, transistor Q2, capacitance Cl, and inductance L
A signal with a frequency fH/2 as shown in FIG. 2c is output to the collector of the transistor Q2 by a tuned amplifier having a tuning frequency fH/2 (fH: horizontal scanning frequency). This signal is then smoothed by the capacitor C2 and the diode D, and the output terminal 3 becomes OV only in the SECAM color state. That is, the circuit shown in FIG. 1 detects the SECAM color state by detecting the difference in the burst signal level of the output of the ceramic filter, and it is difficult to distinguish the SECAM color state from a low level SECAM color signal.

On the other hand, malfunctions are likely to occur when level fluctuations occur in high-level PAL color signals or when large level fluctuations occur. In other words, the lower the SECAM color signal, the more likely the circuit will malfunction, assuming that the level fluctuation rate is constant for the PAL color signal, and the higher the level. In fact, in the circuit shown in Figure 1, when the color killer threshold level is set to the same level as that of a SECAM TV, it is necessary to set the gain of the tunable amplifier to be sufficiently large. Fluctuations in the level of color signals cause malfunctions, and if the original PAL color signal processing is not performed, the reproduced image quality will deteriorate.

The purpose of the present invention is to solve the problems of the above-mentioned conventional method, and to
P, which has the same level of SECAM color killer detection function as CAM TV and does not malfunction due to PAL color signals.
An object of the present invention is to provide a video signal recording and reproducing device capable of recording and reproducing both AL and SECAM type signals.

In the SECAM color killer detection circuit, the color killer threshold level setting for recording and playback is as follows:
It needs to be at a fairly low level, similar to SECAM TV.

However, due to signal processing during recording and reproduction, this low level color signal is sufficiently amplified during reproduction and is supplied to the SECAM color killer detection circuit. Therefore, there is no problem even if the SECAM color killer threshold level during playback is set to a higher level than recording. Focusing on
The present invention thereby also attempts to solve the malfunction caused by PAL and color signals.

In other words, the reproduction SECAM color killer threshold level is set higher than that for recording. This solves the drawbacks of the conventional method described above.

In recording, if the killer threshold level of the SECAM color killer detection circuit is set to the same level as that of the SECAM television, almost no malfunction will occur in PAL and -SECAM signal discrimination.

Furthermore, during recording, when PAL<5SECAM, there is generally no need to perform different signal processing that would affect image quality. However, during playback, the playback color signal level fluctuates due to fluctuations in the running of the magnetic tape, and PAL
-Malfunctions are likely to occur in SECAM signal discrimination. Furthermore, during playback, the signal processing of PAL and SECAM is quite different, so malfunctions may cause deterioration in image quality. In general, in the simple type vm, an automatic color level control circuit (hereinafter abbreviated as ACC) is used for both recording and playback.
It has a function to keep the color signal level constant. Therefore S
SECA at the input of the ECAM color killer detection circuit
The low level color signal near the j color killer threshold level of the M signal is sufficiently amplified during reproduction compared to during recording. A high level of PAL that causes the Ichijo βECAM color killer detection circuit to malfunction. The color signal is not amplified as much during playback as compared to when it is recorded. Yotsute S
The level difference between the input signals of the ECAM color killer detection circuit is smaller during reproduction than during recording. In order to eliminate malfunctions during playback of the SECAM color killer detection circuit, low-level SECAM color signals such as the recording killer threshold should be sufficiently amplified, and high-level PAL color signals should be lowered during playback to prevent the killer detection circuit from malfunctioning. It is desirable to input the information into the ACC, and the function of this ACC corresponds to this.
However, during playback, the PA is at the same level as the SECAM color killer threshold level set during recording.
L. - When performing SECAM signal discrimination, since the threshold level is low, if a high-level PAL color signal is accompanied by level fluctuations, a malfunction occurs and the above-mentioned ACC function cannot be fully utilized. From the above, the low-level SECAM color signal is sufficiently amplified and input to the killer detection circuit during playback, so the SECAM color signal during playback is
If you set the killer threshold level of the color killer detection circuit higher than when recording, this will make it easier to use ECAM.
Malfunctions due to PAL color signal reproduction can be eliminated without impairing color signal detection ability.

An embodiment of the invention is shown in FIGS. 3 and 4. FIG. 3 shows a circuit in which a diode D2, a resistor, and a capacitor C3 are added to the conventional circuit shown in FIG. 1, and a DC voltage is applied to the terminal 4 only during reproduction. Therefore, during reproduction, diode D2 becomes conductive and capacitor F3 is connected to the collector of transistor Q2 constituting the tuned amplifier, so this tuning frequency shifts and the collector output level of Q2 decreases during reproduction. As a result, the color killer threshold level during reproduction becomes higher than that during recording. Also, in Figure 4, the switching level itself of the switching transistor in the final stage is different between recording and playback. During playback, +B is applied to terminal 4, which makes diode D3 conductive, and only during playback does switching transistor O turn on. R3 between base and power supply
is connected, so the switching level of 9 becomes higher during reproduction than during recording. (In this circuit, SECAM
Only in the color state, the killer voltage output terminal 3'' becomes +B voltage.) In addition, the present invention can be realized by changing the level of the burst gate amplifier output itself during recording and reproduction.

According to the present invention, by adding a relatively simple circuit to the conventional circuit, it is possible to solve the malfunction of the SECAM killer detection circuit due to PAL signal reproduction without impairing the original color discrimination ability of SECAM, and to ensure reliable discrimination between PAL and SECAM signals. It can be made into something.

[Brief explanation of the drawing]

Figure 1 is a conventional basic circuit diagram of a SECAM color killer detection circuit, Figures 2 a-c are signal waveform diagrams of the circuit in Figure 1, and Figure 3
FIG. 4 is a circuit diagram showing an embodiment of the present invention.

Claims (1)

[Claims] 1. In a color video signal recording and reproducing device capable of recording and reproducing both PAL and SECAM color video signals,
A color video signal recording and reproducing device comprising: a SECAM color signal discriminating circuit; an automatic color level control circuit; and means for switching the detection level of the SECAM color signal discriminating circuit to be different during recording and during playback. Device.