JP3123062B2 - Frequency multiplexing information signal reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for reproducing a frequency multiplexed information signal.

[Summary of the Invention]

An apparatus for reproducing a frequency multiplexed information signal according to the present invention is a frequency multiplexed information comprising a carrier chrominance signal, a tracking pilot signal having a carrier frequency close to the carrier frequency of the carrier chrominance signal, and the carrier frequency changing in a vertical cycle. In a reproducing apparatus for reproducing signals, a variable trap circuit that traps a tracking pilot signal during variable speed reproduction and does not perform trapping during normal reproduction and a field noise reducer that removes noise due to the tracking pilot signal reproduces a carrier color signal. By providing the circuit, it is possible to prevent the image quality from deteriorating at the time of variable speed reproduction, and to surely expand the band of the carrier color signal at the time of normal reproduction.

[Conventional technology]

In a reproduction system of an 8 mm VTR, providing a trap circuit for trapping a tracking pilot signal in a reproduction circuit of a low-frequency modulated carrier chrominance signal is disclosed in, for example, JP-A-62-214797.
No. 6,086,045.

Hereinafter, the conventional example will be described with reference to FIG. This conventional example shows an 8 mm VTR reproduction system. Although not shown, a rotating magnetic head (a pair of rotating magnetic heads) (1) reproduces a color video signal recorded on a magnetic tape so as to form an inclined track. As shown in FIG. 7, the color video signal is composed of a low-frequency converted carrier color signal having a carrier frequency of 743.444 kHz, a tracking pilot signal on the low frequency side of the low-frequency converted carrier color signal, and a sync chip. And the white level is 4.2 MHz, respectively, FM modulated luminance signal frequency-modulated to correspond to 5.4 MHz, having a band between the band of the low-frequency conversion carrier color signal and the band of the FM modulated luminance signal,
This is a frequency multiplexed signal composed of an FM-modulated audio signal having a carrier frequency of 1.5 MHz.

The tracking pilot signal is composed of four frequency pilot signals, and two different frequency pilot signals are alternately switched for each field.

The color video signal reproduced by the rotating magnetic head (1) is supplied to a high-pass filter (3) and a trap circuit (6) for trapping a frequency-modulated audio signal through a reproduction amplifier (2).

From the high-pass filter (3), an FM-modulated luminance signal is extracted and supplied to a luminance signal processing circuit (4) to limit the amplitude by a limiter, demodulate by an FM demodulation circuit,
De-emphasis etc. are performed by the de-emphasis circuit,
The obtained luminance signal is supplied to the output terminal (5).

The color video signal from the reproduction amplifier (2) is a trap circuit (6) for trapping an FM modulated audio signal, and a trap circuit (7) for trapping a tracking pilot signal.
Is supplied to a low-pass filter (10) to extract a low-pass converted carrier color signal. The low-pass converted carrier color signal is supplied to a carrier color signal processing circuit (11), Processing such as conversion (inverse conversion) is performed, and the resulting carrier chrominance signal is supplied to the output terminal (13).

In the case of an 8 mm VTR, the frequency of the tracking pilot signal changes for each field. Accordingly, the trap circuit (7) is adapted to switch the trap center frequency for each field. Thereby, the band of the carrier chrominance signal composed of the trap circuits (6) and (7) and the low-pass filter (10) is temporarily expanded.

[Problems to be solved by the invention]

However, in such a conventional example, the difference in the trap center frequency for each field in the trap circuit (7) is so small that the effect of expanding the band of the carrier chrominance signal cannot be expected much. If the difference between the frequencies is large, it causes flicker.

In view of the above, the present invention reproduces a frequency multiplexed information signal including a carrier chrominance signal and a tracking pilot signal having a carrier frequency close to the carrier frequency of the carrier chrominance signal, and the carrier frequency changes in a vertical cycle. It is an object of the present invention to propose a reproducing apparatus which can prevent deterioration in image quality in variable speed reproduction and can surely expand the band of a carrier color signal during normal reproduction.

[Means for solving the problem]

The present invention provides a reproducing apparatus for reproducing a frequency multiplexed information signal including a carrier chrominance signal and a carrier frequency close to the carrier frequency of the carrier chrominance signal, and a tracking pilot signal whose carrier frequency changes in a vertical cycle. A frequency multiplexed information signal in which a variable trap circuit that traps a tracking pilot signal during variable speed reproduction and does not trap during normal reproduction and a field noise reducer that removes noise due to the tracking pilot signal are provided in a carrier color signal reproduction circuit. Playback device.

[Action]

According to the present invention described above, the tracking pilot signal is trapped during variable speed reproduction by the variable trap circuit, and the trapping is not performed during normal reproduction, and noise due to the tracking pilot signal is removed by the field noise reducer.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1. In this embodiment, similarly to the conventional example, the present invention is applied to an 8 mm VTR, and FIG. This shows the reproduction system of the millimeter VTR. In FIG. 1, parts corresponding to those in FIG. 6 showing the conventional example are denoted by the same reference numerals, and a duplicate description is partially omitted.

In FIG. 1, the output of a trap circuit (6) for trapping an FM-modulated audio signal is supplied to a trap circuit (7) in which the trap center frequency is switched for each field, as in FIG. A delay unit (8) having the same delay amount as that of the circuit (7) and having neither gain nor delay amount having frequency characteristics is supplied. Then, the outputs of the trap circuit (7) and the delay unit (8) are switched by the changeover switch (9), and the low-pass filter (1) is switched.
0).

This changeover switch (9) is used for variable speed playback of the VTR.
It is switched to the trap circuit (7) side, and is switched to the delay unit (8) side during normal reproduction.

The low-pass conversion carrier color signal extracted by the low-pass filter (10) is supplied to a carrier color signal processing circuit (11), where processing such as high-frequency conversion (inverse conversion) is performed, and the obtained carrier signal is obtained. The color signal is a color field noise reducer (1
2), and the output is output to the output terminal (13).

Next, a specific example of the color field noise reducer (12) in FIG. 1 will be described with reference to FIG. A carrier chrominance signal (including a burst signal) from the carrier chrominance signal processing circuit (7) is supplied to an A / D converter (21) through an input terminal (20) and is converted into a parallel 8-bit digital signal. .
The digital carrier chrominance signal (including the digital burst signal) from the A / D converter (21) is supplied directly to the subtractor (23) and supplied to the field memory (22) to be delayed by one field period. After that, it is supplied to a subtractor (23), the latter is subtracted from the former, and the parallel 9-bit subtraction output is used as an address signal to form a ROM constituting a limiter.
(24).

As shown in FIG. 5, when the level of the input signal supplied to the ROM (24) as an address signal is inside the positive / negative reference level,
The relationship between the level of the input signal and the level of the output signal is linear, and when the level of the input signal is outside the positive / negative reference level, regardless of the increase in the absolute value of the level of the input signal, An 8-bit digital output signal whose level is 0 is stored.

Then, the parallel 8-bit digital output signal from the ROM (24) is regarded as a noise signal and supplied to the subtracter (25) together with the digital carrier color signal from the field memory (22). Is subtracted. Subtractor (29)
Is output to a bit compressor (26), bit-compressed into a parallel 8-bit digital carrier color signal, and then supplied to a D / A converter (27) to be converted into an analog signal. The converted carrier chrominance signal (including the burst signal) is supplied to the output terminal (13) of FIG. 1 through the output terminal (28).

Next, another specific example of the color field noise reducer (12) shown in FIG. 1 will be described with reference to FIG. 4. In FIG. 4, the same reference numerals are given to parts corresponding to FIG. Then, a duplicate description will be partially omitted. The parallel 8-bit digital carrier chrominance signal (including the digital burst signal) from the A / D converter (21) is supplied directly to the subtracters (29) and (30). The parallel 9-bit subtraction output from the subtractor (29) is
After being supplied to the bit compressor (26) and bit-compressed into a parallel 8-bit digital signal, the field memory (2
2) and is delayed by one field period. The output of the field memory (22) is output from the D / A converter (2
7) and supplied to the subtractor (30),
It is subtracted from the digital carrier chrominance signal (including the burst signal) from the / D converter (21), and the parallel 9-bit subtraction output is supplied to the ROM (24) as a limiter.

Then, the parallel 8-bit digital output signal from the ROM (24) is regarded as a noise signal and supplied to a subtractor (29) to subtract from the digital carrier color signal from the A / D converter (21). Is done.

Next, the operation of the embodiment of FIG. 1 will be described. At the time of variable speed reproduction, the changeover switch (9) is set to the trap circuit (7).
It is switched to the side. During variable speed reproduction such as a picture search, the frequency of the tracking pilot signal in the previous field and the current field partially coincides with each other due to head skew before and after switching of the pair of rotating magnetic heads, fluctuation in running of the magnetic tape, and the like. Cases arise. in this case,
Depending on the color field noise reducer (12),
Although the tracking pilot signal as an interfering wave for the carrier chrominance signal cannot be reliably removed, image quality deterioration can be prevented by trapping the tracking pilot signal by the trap circuit (7).

Note that the frequency of the tracking pilot signal does not change during still image reproduction because it is a field still, and the tracking pilot signal as an interference wave for the carrier chrominance signal cannot be removed by the color field noise reducer (12).

At the time of normal reproduction, the changeover switch (9) is switched to the side of the delay unit (8). In this case, the color field noise reducer (12) reduces the interference wave beat due to the tracking pilot signal as the interference wave for the carrier color signal, so that the beat noise on the reproduction screen becomes invisible. As a result, the band of the carrier chrominance signal restricted by the tracking pilot signal can be expanded in the same manner as when there is no tracking pilot signal.

 Note that the delay unit (8) does not necessarily need to be provided.

Although the embodiment of FIG. 1 described above is the case where the present invention is applied to an 8 mm VTR, the present invention can also be applied to a Beta Hi-Fi VTR. In a Beta Hi-Fi VTR, a color video signal recorded on a magnetic tape so as to form an inclined track is composed of a low-frequency converted carrier color signal having a carrier frequency of 688 kHz, a sync chip and a white level as shown in FIG. It has a band between an FM-modulated luminance signal frequency-modulated to correspond to 4 MHz and 5.17 MHz, a band of a low-frequency converted carrier chrominance signal, and a band of an FM-modulated luminance signal, respectively.
The frequency carrier signal is different for each field from two different
This is a frequency multiplexed signal composed of a frequency-modulated audio signal that is alternately switched to a carrier signal of a frequency.

Therefore, although the reproduction circuit of the embodiment in which the present invention is applied to the Beta Hi-Fi VTR is not shown, the trap circuit (6) is omitted in the embodiment of FIG. Instead, a trap circuit for trapping a frequency-modulated audio signal whose center frequency is switched for each field is provided. Other configurations are the same as those of the embodiment of FIG. However, various constants and characteristics in the low-pass filter (10), the carrier color signal processing circuit (11) and the color field noise reducer (12) depend on the frequency allocation of the color video signal recorded on the magnetic tape of the Beta Hi-Fi VTR. Of course, it is set.

〔The invention's effect〕

According to the present invention described above, a frequency multiplexed information signal composed of a carrier chrominance signal and a tracking pilot signal having a carrier frequency close to the carrier frequency of the carrier chrominance signal and whose carrier frequency changes in a vertical cycle is reproduced. In the reproducing apparatus, a variable trap circuit that traps a tracking pilot signal during variable speed reproduction and does not trap the tracking pilot signal during normal reproduction and a field noise reducer that removes noise due to the tracking pilot signal are provided in the carrier color signal reproduction circuit. Therefore, it is possible to obtain a frequency multiplexed information signal reproducing apparatus that can prevent image quality deterioration during variable speed reproduction and can reliably expand the band of the carrier chrominance signal during normal reproduction.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing frequency allocation of a recording signal in a Beta Hi-Fi VTR, and FIGS. 3 and 4 each show a specific example of a color field noise reducer. Block diagram,
FIG. 5 is a curve diagram showing characteristics of a limiter, FIG. 6 is a block diagram showing a conventional example, and FIG. 7 is a diagram showing frequency allocation of a recording signal in an 8 mm VTR. (1) is a rotating magnetic head, (3) is a high-pass filter,
(4) is a luminance signal processing circuit, (6) and (7) are trap circuits, (8) is a delay unit, (9) is a changeover switch,
(10) is a low-pass film, (11) is a carrier color signal processing circuit, and (12) is a color field noise reducer.

Claims (1)

(57) [Claims] A reproducing apparatus for reproducing a frequency multiplexed information signal comprising a carrier chrominance signal and a tracking pilot signal having a carrier frequency close to the carrier frequency of the carrier chrominance signal, wherein the carrier frequency changes in a vertical cycle. A variable trap circuit that traps the tracking pilot signal during variable-speed reproduction and does not trap the tracking pilot signal during normal reproduction, and a field noise reducer that removes noise due to the tracking pilot signal, are provided in the carrier color signal reproduction circuit. An apparatus for reproducing a frequency-division multiplexed information signal.