JPS5897114A - Nonlinear emphasis circuit - Google Patents

Abstract

PURPOSE:To decrease the noise at an edge of a reproduced video signal, by providing an LPF for a nonlinear emphasis circuit having an HPF, a compressor, and an attenuator for a VTR or the like, bringing a cut-off frequency of the HPF into higher frequencies for the provision of the LPF and decreasing the attenuation. CONSTITUTION:A reproduced video signal of nonlinear preemphasis is inputted to an input terminal 7 at recording, a high frequency component is picked up at an HPF8, and a large amplitude part is compressed at a compressor 9. After the component is applied to an LPF13, the level is attenuated to a suitable level at an attenuator 10, and a signal difference with the input signal to the terminal 7 is produced at an output terminal 12 of a subtractor 11. The characteristics as shown in 16 in figure are obtained as the output of the compressor 9, the characteristics shown in 15 are obtained at the LPF13, this is suitably attenuated at the attenuator 10, to obtain the nonlinear deemphasis characteristic as shown in 14. As a result, in comparison with the conventional curve 7, the cut-off frequency is shifted to high frequencies, the noise at the edge is reduced, allowing to obtain the nonlinear emphasis circuit having improved S/N.

Description

[Detailed Description of the Invention] The present invention provides a magnetic recording and reproducing @ for recording and reproducing video signals, etc.
This invention relates to improving the characteristics of the nonlinear emphasis circuit of the 111 (hereinafter referred to as VTR).

In 1/TR for 1 garden, S/! In order to improve V, in addition to normal emphasis, non-linear emphasis is performed which changes the emphasis percentage according to the signal level.

Conventional non-linear 7° used in VTRIC for crocodile gardens
Figure 2 shows the configuration of a conventional non-linear de-emphasis circuit. 1st
In the figure, 1 is an input terminal, 2 is a no-pass filter (
Hereinafter referred to as BPF, 5 is a compressor, 4 is an attenuator, 5 is an adder, 6 is an output terminal, and the input terminal 1vc is used to remove the color component of the video signal to be recorded, and to remove only the bright # signal. can be input. The high-frequency components of one of the input signals are extracted by the BrF3, and the large amplitude parts are compressed by the next compressor 3. The output of the compressor 3 is attenuated to an appropriate level by an attenuator 4 in the next stage, added to the signal inputted to the input terminal 1, and outputted from the output terminal 6.

Further, in Fig. 2, 7 is an input terminal, 8 is a BPF, and 9 is an input terminal.
1 is a compressor, 10 is a subtractor, 11 is a subtracter 12, and an input terminal 7 receives a reproduced video brightness f signal that has been nonlinearly pre-emphasized during recording. One of the input signals is subjected to a BPF 8 in which high-frequency components are extracted, and a subsequent compressor 9 compresses large amplitude portions. Compressor 9
The output is attenuated to an appropriate level by the attenuator 10 in the next stage, and then subtracted from the signal input to the input terminal 7 and output from the output terminal 12.

An example of the characteristics of the nonlinear pre-emphasis circuit shown in FIG. 11 is shown in FIG. Figure 5 shows the relationship between frequency and response using input level as a parameter.
Due to the effect of compressor 3 shown in Figure @1, almost no pre-emphasis is applied when the input level is large (QctB), but when the input level becomes low, the high frequency response increases and pre-emphasis is applied significantly. It has become. Further, an example of the characteristics of the nonlinear de-emphasis circuit shown in FIG. 2 is shown in FIG. In the non-linear de-emphasis circuit, due to the effect of compressor 9,
When the input level is high, almost nothing is subtracted from the original signal, but when the input level becomes low, the high frequency components of the input signal are significantly subtracted, and the nonlinear pre-emphasized signal is nonlinearly de-emphasized.

In this way, for a signal with a low level, the high frequency range of the signal is avoided during recording, and the high frequency range is conversely suppressed during playback, thereby improving s7h. Note that non-linear emphasis has no effect of improving #1 s7h for large amplitude signals, and is used in combination with normal emphasis.

However, in this prior art, there is a drawback that noise can hardly be completely removed in the so-called edge portions where the level change is suddenly large in the reproduced taste gII signal subjected to non-linear de-emphasis. This will be explained using the waveform diagram shown in Figure @5. The waveform shown in Figure 5 (α) is
When nonlinear pre-emphasis is applied, the waveform shown in Fig. 5 (bl) is obtained, and it is magnetically recorded. At the time of playback, the waveform shown in Fig. 145 (bl) is the same as that shown in Fig. The waveform shown in Fig. 5 (cl) is obtained. This wJs diagram (the signal of cl is supplied with the nonlinear de-emphasis times # & D, and is subtracted by the output of the attenuation gM1o shown in Fig. 5 ←), At the output terminal 12, the waveform has a lot of noise at the edge portion indicated by 5-(gl).

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art.
K provides a non-linear engine 7 assist circuit that can also improve the edge response.

In order to achieve the above object, the present invention provides a bypass 71
In the non-linear engine 7 assist@il, which is equipped with a filter, a compressor, and an attenuator, a low-pass filter is installed, and the cutoff frequency of the bypass filter is increased accordingly, and the amount of attenuation of the attenuator is reduced accordingly. This reduces noise at the edges of the video signal.

The present invention will be explained below using examples. FIG. 6 is a diagram showing an embodiment of the nonlinear de-emphasis circuit of the present invention, and FIGS. 7 and 8 are diagrams explaining the present invention in detail. In Fig. 6, 1S is a filter (hereinafter referred to as LP).
(abbreviated as F), and parts that are equivalent or the same as those of the conventional example are given the same numbers. A reproduced video signal that has been non-linearly pre-emphasized during recording is input to the input terminal 7, and high frequency components of one of the input signals are extracted by BpF f3 and then compressed! 9, the large amplitude portion is compressed. The output of this compressor 9 is then supplied to the LP 115, and then
The signal is attenuated to an appropriate level by the attenuator 10, subtracted from the signal input to the input terminal 7, and output from the output terminal 12.

Next, the operating characteristics of the present invention will be explained using FIGS. 7 and 8. Now, in response to the non-linear pre-emphasis characteristic, w
When trying to obtain the non-linear de-emphasis curve shown in Figure 14, in the conventional configuration, the output characteristic of the compressor 9 shown in Figure 17 is appropriately attenuated by the attenuator 10. In contrast, in the present invention, the characteristics shown in @7 FIG. 16 are obtained as the output of the compressor 9, and then the characteristics shown in FIG.
1K, and the desired nonlinear de-emphasis characteristic shown in w4Z FIG. 14 is obtained. That is, the output characteristic of the compressor becomes a characteristic (curve 16) in which the cutoff frequency is shifted to a higher frequency range compared to the conventional one (curve 17), and the time constant of the BPF can be reduced. Further, the amount of attenuation of the reduction & mackerel is smaller in the present invention (difference between curve 15 and curve 14) than in the conventional case (difference between curve 17 and curve 14). Next, the edge noise reduction effect at this time will be explained using FIG. 8. As in the conventional case, the video signal shown in FIG. 8 (α) is non-linearly pre-emphasized and becomes the waveform shown in FIG. 8 (b), which is recorded clearly. During playback, the waveform shown in FIG. 8 (cl.
The waveform shown in is obtained and supplied to the nonlinear de-emphasis circuit. This FIG. 8 (cl signal is subtracter 11
8 (d
)K As shown, a subtraction signal with a small attenuation amount and a small time constant is input to the subtracter 11 compared to the conventional method. Therefore, the output terminal 12 is connected to the terminal shown in FIG.
) A reproduced video signal with less noise at the edges can be obtained compared to the conventional reproduced video signal shown in ( ).

Although there is some waveform distortion in Figure 8,
This is because the non-linear pre-emphasis circuit does not have the above-mentioned LpF, and if the above-mentioned LPF is also provided in the non-linear pre-emphasis circuit, the above-mentioned waveform distortion can be eliminated. Next, this point will be explained. FIG. 9 shows a non-linear pre-emphasis circuit when an LPF is provided, 18 is the LPF, and the other parts are the same or the same as those in FIG. 1 and are given the same numbers. 1149
FIG. 10 shows waveform changes when the nonlinear emphasis circuit shown in FIG. 6 and FIG. 6 is operated. Figure 10 (
α) is.

Record video gII4! No., the above LP118 shown in Figure 9
After passing through a nonlinear pre-emphasis circuit equipped with V, a waveform as shown in FIG. 10(b) is obtained.

The signal in FIG. 10(b) is supplied to the magnetic recording and reproducing system,
During reproduction, a waveform as shown in FIG. 10(C) is obtained.

Below, the machine operates in the same way as in the case of the above-mentioned embodiment, and as shown in Fig. 10 (-
), a reproduced film waveform without a waveform pot and with less edge noise can be obtained.

As described above, according to the present invention, the S/Iv Y of the edge portion (the portion where the level change is suddenly large) of the reproduced video signal is
: It is possible to realize a non-linear emphasis circuit that can be improved to a large size.

[Brief explanation of the drawing]

Figure 1 is a conventional non-linear pre-emphasis circuit diagram.
Figure 92 is a conventional non-linear de-emphasis circuit diagram, Figure 5 is a desired characteristic diagram of a non-linear pre-emphasis circuit,
@ Figure 4 is a desired characteristic diagram of a non-linear de-emphasis circuit, Figure 5 is a diagram explaining the operation of a conventional non-linear de-emphasis circuit, Figure 6 is a diagram of an embodiment of a non-linear de-emphasis circuit according to the present invention, and Figure 7 , FIG. 8, and FIG. 10 are diagrams explaining the present invention in detail, and FIG. 9 is a diagram showing an embodiment of the nonlinear pre-emphasis circuit according to the present invention. 1.7...Input terminal 2.8...BpF5.9
... Compression - 4, 10 ... Attenuation - B ... Addition 1iF
6.12...Output terminal 11...Subtraction -15118.
... LPF Patent Attorney Susuki 1) Toshiyuki 1'1 Figure 1 Evening 6, t Figure 74. Figure 5' Figure '2 6 Figure 7 7 Figure 8 Figure 1'9 Figure 10

Claims (1)

[Claims] t In a non-linear emphasis circuit equipped with a bypass filter, a compressor, an attenuator, and a mixer, a low-pass filter is provided in the signal system passing through the bypass filter, the compressor, and the attenuator. 7 assist circuit.