JPS6281894A - 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 the carrier color signal to a low-pass converted carrier color signal, record it, and then frequency-convert it again to the carrier color signal during playback. This is a method called color under.

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

FIG. 2 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 up) 2, and then sent to a low-pass 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 bandpass filter (BPF) 6 to remove unnecessary components that occur during balanced modulation, and is further filtered by a comb filter 7 to remove crosstalk from adjacent trunks. Sent to 9th. A burst gate circuit 9 extracts the burst from the carrier color signal and connects it to a first comparator 10 and a second comparator 12.
sent to. The first comparator 10 converts the burst level into AC
The burst level is compared with the ACC reference level output from the C reference level generator 11, and if the burst level is lower than the XX reference level, a control signal is output to increase the amplification factor of the ACC amplifier 4, and the burst level is set to ACC. If the level is higher than the reference level, 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 7 is output 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.

FIG. 3 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 AC during standard mode playback.
Set the standard burst level of the input of C amplifier 4 (the burst level when recording and playing back a standard level color signal) to o.
[dB], and the vertical axis indicates the standard burst level of the output of the burst gate circuit 9 during standard mode reproduction as O (dB). ACC Ang 4 input burst level is -2
In the region above 0 (dB), the burst level of the output of the burst gate circuit 9 is kept constant by the action of the ACC loop.However, since there is a limit to the amplification factor of the ACC amplifier 4, In the region where the input burst level is below -20 [dB], the ACC amplifier 4
The burst level of the burst gate circuit 9 output also decreases in proportion to the decrease of the input no(-st level).If the killer reference level is set to -10 [dB], the input of the ACC amplifier 4 The burst level of 13o (
By the way, the output switch 8 will be switched at dB.

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, :l) lower than the standard burst level during standard mode playback. The standard burst level during long-time mode playback at the input of amplifier 4 is 4 [dB] lower than the standard burst level during standard mode playback. Therefore, in the configuration described above, standard mode playback Time killer level (standard parse of ACC amplifier 4 input) L/
ACC for bevel when output switch 8 switches
Amplifier 4 input burst level. ) is -3o [dJ], whereas the killer level during long-time mode playback is -30-(-4) knee 26 [dB], which is 4 [dB] higher. Therefore, when the burst level of the reproduced signal obtained from the recording medium becomes low, there is a problem that in the long-time mode, the switch 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 first input amplifier that amplifies the reproduction signal obtained from the recording medium, and a first input amplifier that amplifies the reproduction signal obtained from the recording medium. A second input amplifier amplifies with a larger amplification factor than the first input amplifier, and an output of the first input amplifier is selected during standard mode reproduction.

and switch means for selecting the output of the second input amplifier during long-time mode reproduction.

Effect of the Invention With the above-described configuration, the present invention makes it possible to effectively 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. It becomes possible.

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 a first input amplifier, 3 is a low-pass filter (LPF), and 4 is an ACC
amplifier, 5 is a balanced modulator, 6 is a bandpass filter (B
PF), 7 is a filter, 8 is an output switch, 9 is a burst gate circuit, 1o is a first comparator, 11 is an AC
12 is a second comparator, 13 is an output terminal, 14 is a killer reference level generator, 15 is a switch, 16 is a second input amplifier, and 17 is a mode switching signal input terminal.

The operation of the color signal reproducing apparatus of this embodiment configured as described above will be described below with reference to FIG. 1. In FIG. 1, a reproduced signal obtained from a recording medium is inputted from a reproduced signal input terminal 1 and sent to a first input amplifier 2 and a second input amplifier 16. The reproduction signal sent to the first input amplifier 2 is amplified and sent to the switch 16.

On the other hand, the reproduction signal sent to the second input amplifier 16 is
The signal is amplified with an amplification factor approximately 4 dB larger than the amplification factor of the input amplifier 2 of , and is sent to the switch 16 . The switch 16 is controlled by a mode switching signal input from a mode switching signal input terminal 17.

During standard mode reproduction, the switch 15 is switched to the SP side, and the output of the first input amplifier 2 is sent to the low-pass filter 3. During long-time mode playback, switch 16 is set to L.
Switching to the P side, the output of the second input amplifier 16 is sent to the low-pass filter 3. The operation after the low-pass filter 3 is similar to the conventional example shown in FIG.

At the input terminal 1, the standard burst level during long-time mode reproduction is approximately 4 [dB] lower than the standard burst level during standard mode reproduction.

However, since the amplification factor of the second input amplifier 16 is set 4 [dB] larger than the amplification factor of the first input amplifier 2, the standard burst level during long-time mode playback is The standard pulse level during standard mode playback is the same level. Therefore, the killer level during long-time mode playback is the same as the killer level during standard mode playback.

As described above, according to this embodiment, the first input amplifier amplifies the reproduced signal obtained from the recording medium, and the second input amplifier amplifies the reproduced signal obtained from the recording medium with a larger amplification factor than the first input amplifier. 2 input amplifiers and a switch means for selecting the output of the first input amplifier during standard mode playback and selecting the output of the second input amplifier during long time 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, FIG. 2 is a block diagram of a main part of an example of a conventional color signal reproducing device, and FIG. 3 shows a burst level of the input of the ACC amplifier in FIG. 7 is a graph showing the relationship between the burst levels of the output of the burst gate circuit. 1... Reproduction signal input terminal, 2... First input amplifier, 3... Low pass filter, 4...
・ACC7 amplifier, 5...Balanced modulator, 6...
...Band pass filter, 7...Comb filter,
8... Output switch, 9... Burst gate circuit, 1o...; gl comparator, 11...A
CC reference level generator, 12...second comparator, 13...output terminal, 14...killer reference level generator, 15...switch, 16th 2nd
Input amplifier, 17...Mode switching signal input terminal. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
figure

Claims (1)

[Claims] A first input amplifier for amplifying a reproduced signal obtained from a recording medium in a video tape recorder in which a carrier color signal is frequency-converted into a low-frequency converted carrier color signal for recording, and is inversely converted and returned to the carrier color signal during playback; a second input amplifier that amplifies a reproduction signal obtained from a recording medium with a larger amplification factor than the first input amplifier;
1. A color signal reproducing apparatus, comprising: a switch means for selecting an output of said input amplifier; and a switch means for selecting an output of said second input amplifier during long-time mode reproduction.