JPS6281893A - color signal regenerator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a color signal reproducing device in a video tape recorder.

Conventional technology Conventionally, the color signal processing method used in consumer video tape recorders is to frequency-convert a carrier color signal to a low-pass converted carrier color signal and record it, and then convert the frequency again during playback to create a carrier color signal. This is a method called color under that returns the color to the original color.

Hereinafter, a conventional color under one type color signal reproducing device will be described with reference to the drawings.

FIG. 3 is a block diagram of an example of a conventional color under one type reproducing apparatus. In the figure, a reproduced signal obtained from a recording medium is inputted from a reproduced signal input terminal 1, amplified by an input amplifier (hereinafter referred to as input amplifier) 2, and then sent to a low filter filter (LPF) 3. The low-pass filter 3 extracts a low-pass conversion carrier color signal from the reproduced color signal, and converts it into an ACC (Automatic Chroma) signal.
control) is sent to amplifier 4. The low frequency converted carrier color signal whose level has been adjusted by the ACC amplifier 4 is frequency converted by the balanced modulator 5 and becomes a carrier color signal. This carrier color signal is filtered by a band pass filter (BPF) 6 to remove unnecessary components generated during balanced modulation, and further removed by a comb filter 7 to remove crosstalk from adjacent tracks. The signal is sent to the output circuit 9. A burst gate circuit 9 extracts the burst from the carrier color signal and connects the first comparator 10 and the second comparator 1.
Sent to 2. The first comparator 1o sets the burst level to A
When the burst level output from the CC reference level generator 11 is lower than the ACC reference level, a control signal is output to increase the amplification factor of the ACC amplifier 4, and the burst level is lower than the ACC reference level. If the amplification factor of the ACC amplifier 4 is also high, a control signal is output to reduce the amplification factor of the ACC amplifier 4. In this way, an ACC loop is formed that keeps the burst level of the output of the burst gate circuit 9 constant.

On the other hand, the second comparator 12 compares the burst level with the killer reference level output from the killer reference level generator 14 and outputs a signal for controlling the output switch 8 . If the burst level is higher than the killer reference level, the second comparator 12 outputs a control signal that turns the output switch 8 on. At this time, the carrier color signal output from the comb filter is outputted from the output terminal 13.

If the burst level is lower than the killer reference level, the second comparator 12 turns off the output switch 8.
Generates a control signal to set the state.

At this time, no carrier color signal is output from the output terminal 13.

41-1 is a graph showing the relationship between the burst level of the input of the ACC amplifier 3 and the burst level of the output of the burst gate circuit 9. However, the horizontal axis is the standard burst level of ACC amplifier 40 input during standard mode playback (burst level when recording and playing back a standard level color signal)
is o [dB], and the vertical axis is the standard burst level of the output of the burst gate circuit 9 during standard mode playback, o [dB].
It is said that In a region where the burst level of the input of the ACC amplifier 40 is -20 (dB) or higher, the burst level of the output of the burst gate circuit 9 is kept constant by the action of the ACC loose. However, since there is a limit to the amplification factor of the ACC amplifier 4, in the region where the burst level of the input to the ACC amplifier 4 is below 12o (dB), the burst level of the input to the ACC amplifier 4 decreases in proportion to the decrease. Therefore, the burst level of the output of the burst gate circuit 9 is also low.

When the killer reference level is set to -10 [dB], A
The burst level of the input of CC amplifier 4 is -30[:dB
The output/output switch will change at :].

Problems to be Solved by the Invention By the way, the standard burst level during long-time mode playback at the playback signal input terminal 1 is about 4 [:dB] lower than the standard burst level during standard mode playback. The standard burst level at the input of the amplifier 4 during long-time mode reproduction is 4 (dB) lower than the standard burst level during standard mode reproduction. Therefore, in the above configuration, the killer level during standard mode playback (relative to the standard burst level of the input of the ACC amplifier 4; the burst level of the input of the ACC amplifier 4 when the output switch 8 is switched) is -30 [dB]. ], whereas the killer level during long mode playback is -3
0-(-4) = -2e CdBl), which is higher by 4 [dB:]. For this reason, when the burst level of the reproduction signal obtained from the recording medium becomes low, there is a problem that in the long-time mode, the Inochi 8 is more likely to turn off than in the standard mode, that is, the color is likely to fade. .

In view of the above problems, the present invention provides a color signal reproducing device that can prevent color fading during long-time mode playback by making the killer level during long-time mode playback the same as the killer level during standard mode playback. It is something to do.

Means for Solving the Problems In order to solve the above problems, the color signal reproducing device of the present invention includes a burst gate means for extracting a burst signal from a carrier color signal, and an amplification means for amplifying the output of the burst gate means. and switch means for selecting the output of the burst gate means during standard mode reproduction and selecting the output of the amplification means during long time mode reproduction.

Effect: With the above-described configuration, the present invention makes it possible to prevent color fading during long-time mode playback by setting the killer level during long-time mode playback to the same level as the killer level during standard mode playback. .

Embodiments Hereinafter, embodiments of the color signal reproducing device of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of essential parts of an embodiment of the present invention. In Fig. 1, 1 is a reproduction signal input terminal, 2 is an input amplifier, 3 is a low-pass filter (LPF), 4 is an ACC amplifier, 5 is a balanced modulator, and 6 is a band-pass filter (BPF).
, 71d<L-type filter, 8 is an output switch, 9 is a burst gate circuit, 10 is a first comparator, 11 is an ACC reference level generator, 12 is a second comparator, 13 is an output terminal, 14 is a killer Reference level generator, 16 is a switch, 1
6 is a burst amplifier, and 17 is a mode switching signal input terminal.

The operation of the color signal reproducing device of this embodiment configured as described above will be described below with reference to FIGS. 1 and 2.

In FIG. 1, switch 16 is controlled by a mode switching signal inputted from mode switching signal input terminal 17. In FIG. In the case of standard mode reproduction, the switch 15 is switched to the SP side, and the output of the burst gate circuit 9 is sent as is to the second comparator 12.

On the other hand, in the case of long-time mode playback, the switch 15 is set to L.
The output of the burst gate circuit 9 is switched to the P side, and the output of the burst gate circuit 9 is amplified by 4 [dB] by the burst amplifier 16 and then sent to the second comparator 12. This point is different from the conventional color signal reproducing device shown in FIG. 3, and the other parts operate in the same way.

FIG. 2 is a graph showing the relationship between the burst level of the input of the ACC amplifier 4 and the burst level of the output of the switch 16. However, the horizontal axis is the ACC amplifier 4 during standard mode playback.
The standard burst level of the input is o (dB), and the vertical axis is o (dB) the standard burst level of the output of the switch 15 during standard mode reproduction. In the figure, a is a graph for standard mode reproduction, and b is a graph for long time mode reproduction. Killer reference level -1o (dB)
(The burst level of the output of the burst gate 9 during standard mode playback is set to o (dB).) When the burst level of the input of the ACC amplifier 4 is set to 13 o (dB:l) during standard mode playback, Switch 8 changes (
(See Figure 2 a). Therefore, the killer level during standard mode reproduction is -30 [dB].

On the other hand, during long-time mode playback, when the input burst level of ACC amplifier 4 is -34 (dB), switch 8
is switched (see b in Figure 2). The standard burst level at the input of ACC amplifier 4 during long-time mode playback is 4[:dB:] lower than the standard burst level at the input of ACC amplifier 4 during standard-mode playback. The killer level is -34-(-4)=-so(
dB).

As described above, according to this embodiment, the burst gate means (circuit) extracts the burst signal from the carrier color signal, the amplification means (burst amplifier) amplifies the output of the burst gate means, and the burst signal Select the output of the gate means.

By configuring the apparatus to include a switch means for selecting the output of the amplifying means during long-time mode playback, the killer level during long-time mode playback can be made the same as the killer level during standard mode playback, Color fading during long-time mode playback can be effectively prevented.

Effects of the Invention As described above, according to the present invention, excellent effects such as being able to effectively prevent color fading during long-time mode playback can be obtained with a relatively simple configuration.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a main part of an embodiment of the present invention, and FIG. 2 is a graph showing the relationship between the burst level of the input of the ACC amplifier and the burst level of the output of the switch in FIG.
FIG. 3 is a block diagram of an example of a conventional color signal reproducing device, and FIG. 4 is a graph showing the relationship between the burst level of the input of the ACC amplifier in FIG. 3 and the burst level of the output of the Hurst gate circuit. 1...Reproduction signal input terminal, 2...Input amplifier, 3...Low pass filter, 4...
...ACC amplifier, 6...Balanced modulator, 6...
...Band pass filter, 7...Comb filter, 8...Output switch, 9...
Burst gate circuit, 1o...first comparator,
11...+++ A CC reference level generator, 12.
...Second comparator, 13...Output terminal,
14... Killer reference level generator, 15...
...Switch, 16...Burst amplifier, 1
7...Mode switching signal input terminal. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 2
Figure AC (, burst level of amplifier 4 [t8] Figure 4)

Claims (1)

[Claims] In a video tape recorder, a carrier color signal is frequency-converted into a low-pass converted carrier color signal and recorded, and upon playback, the carrier color signal is inversely converted and returned to the carrier color signal, comprising a burst gate means for extracting a burst signal from the carrier color signal, and the burst gate means. and a switch means that selects the output of the burst gate means during standard mode reproduction and selects the output of the amplification means during long time mode reproduction. Device.