JPS6281895A - 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 amplifier) 2, and then sent to a low-pass filter (LPF) 3. A low-pass conversion carrier color signal is extracted from the reproduced color signal by a low-pass filter 3, and is converted into an ACC (Automatta Chroma C
(ontrol) The low frequency conversion carrier color signal whose level has been adjusted by the oACC amplifier 4 and which is sent to the amplifier 4 is sent to the balanced modulator 6.
The signal is frequency-converted and becomes a carrier color signal. This carrier color signal is filtered by a bandpass filter (BPF) e to remove unnecessary components that occur during balanced modulation, and is further filtered by a comb filter 7.
After removing crosstalk from adjacent tracks, the signal is sent to an output switch 8 and a burst gate circuit 9. A burst gate circuit 9 extracts the burst from the carrier color signal and sends it to a first comparator 10 and a second comparator 12 . The first comparator 10 compares the burst level with the ACC reference level output from the ACC reference level generator 11, and when the burst level is lower than the ACC reference level, a control signal is provided to increase the amplification factor of the ACC amplifier 4. The burst gate circuit 9 outputs a control signal that reduces the amplification factor of the ACC amplifier 4 when the burst level is higher than the ACC reference level.
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 the output switch 8 Outputs a signal to control the 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 Hurst gate circuit 9. However, the horizontal axis is the AC during standard mode playback.
Set the standard burst level (burst level when recording and playing back a standard level color signal) of the input of C amplifier 4 to ○.
(aB) The vertical axis indicates the standard burst level of the output of the burst gate circuit 9 during standard mode reproduction as 0 (dB). The burst level of the input of ACC amplifier 4 is -2
In the region of 0 (dB) or more, 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 of the ACC amplifier 4 is below -20[:dB], the burst level of the input of the ACC amplifier 4 becomes proportional to the lower value. 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), the burst level of the input of ACC amplifier 4 is -13o.
(dB), the output switch 8 is switched.

Problem 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, so the ACC amplifier 4 The standard burst level during long-time mode playback at the input is 4 [dB] lower than the standard burst level during standard mode playback.
In the configuration described above, the killer level (ACC amplifier 4 when the output switch 8 is switched with respect to the standard burst level of the ACC amplifier 40 input) during standard mode playback is
input burst level) is -30 (dB), while the killer level during long-term mode playback is -30 (dB).
-(-4)=-26(dB), which is 4(dB) higher.For this reason, when the burst level of the playback signal obtained from the recording medium becomes low, the long time mode is higher than the standard mode. There is a problem in that it is easy to be turned off when the base switch 8 is turned off, that is, the color is easy 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 killer reference level generator that outputs a first killer reference level; a second killer reference level generator that outputs a second killer reference level lower than the second killer reference level, and selects the output of the first killer reference level generator during standard mode playback, and selects the output of the first killer reference level generator during long time mode playback. and switch means for selecting the output of the killer reference level generator.

Effect: With the above-described configuration, the present invention makes it possible to effectively 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 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 Figure 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, 6 is a balanced modulator, and 6 is a band-pass filter (BPF).
, 7 is a comb-shaped 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 first killer reference level generator, 16 is a second killer reference level generator, 16 is a switch, 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.

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 playback, the switch 16 is switched to the SP side 9, and the first killer reference level output from the first killer reference level generator 14 is sent to the second comparator, and the burst gate circuit 9 is compared with the burst level of the output.

On the other hand, in the case of long-time mode playback, the switch 16 is switched to the LP side, and the second killer reference level output from the second killer reference level generator 16 is sent to the second comparator, and the second killer reference level is sent to the second comparator. It is compared with the burst level of the output of the gate circuit 9. This point is different from the conventional color signal reproducing device shown in FIG. 2, and other parts are the same. The first killer reference level is -1ow:dB), and the second killer reference level is -14(dB) (the standard burst level of the output of the burst gate circuit 9 during standard mode playback is o(dB)). 3, the burst level of the input to the ACC amplifier 4 when the output switch 8 is switched is -30 in the case of standard mode playback.
[dB), -34 (dB:] for long time mode playback)
becomes. Therefore, the killer level is -30-0=-30 (dB) in the case of standard mode playback.

For long-term remote playback, -3a-(-4)=-so(
:dB).

As described above, according to this embodiment, the first killer reference level generator outputs the first killer reference level, and the second killer reference level generator outputs the second killer reference level lower than the first killer reference level. The second killer reference level generator and the output of the first killer reference level generator are selected during standard mode playback.

By providing a switch means for selecting the output of the second killer reference level generator during long-time mode playback, the killer level during long-time mode playback can be set to the same level as the killer level during standard mode playback. This makes it possible to prevent color fading during long-time mode playback.

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

[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 is a block diagram of a main part of an example of a conventional color signal reproducing device. 7 is a graph showing the relationship between the output and the burst level. 1... Reproduction signal input terminal, 2... Input amplifier, 3... Low pass filter, 4...
...ACC amplifier, 5...Balanced modulator, 6...
...Band pass filter, 7...Comb filter, 8...Output switch, 9...
burst gate circuit, 10...first comparator,
11...ACC reference level generator, 12...
...Second comparator, 13... Output terminal, 14.
...First killer reference level generator, 16...
...Second killer reference level generator, 16...
・Switch, 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 killer reference level is generated for outputting a first killer reference level in a video tape recorder that frequency-converts a carrier color signal into a low-pass converted carrier color signal and records it, and inversely converts it and returns it to the carrier color signal during playback. a second killer reference level generator that outputs a second killer reference level lower than the first killer reference level; and a second killer reference level generator that selects the output of the first killer reference level generator during standard mode playback. ,
1. A color signal reproducing device comprising: switch means for selecting the output of the second killer reference level generator during long-time mode reproduction.