JP2778018B2 - Low-pass replacement circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a low-pass replacement circuit, and in particular, is applicable to a reproduction device (decoder) of a multiplex sub-sample transmission signal.

[Related Art] As one of the systems for transmitting a television signal after compressing the band, there is a multiplex sub-sample transmission system using offset sampling between frames and between fields. This multiplex sub-sample transmission system is also adopted as a transmission system for high-definition television signals, and a system for high-definition television signals proposed by the Japan Broadcasting Corporation is called a MUSE system.

Therefore, the reproduction apparatus of the transmission signal according to the MUSE system, that is, the MUSE decoder performs a decoding process such as an inter-frame interpolation process, an inter-field interpolation process, a field interpolation process, a noise reduction process, etc., as needed, to perform a high-definition television signal. To play.

By the way, the transmission signal according to the MUSE system has a low frequency range (0 to 0).
4 MHz) does not include a folded component between frames, so that a problem occurs even if the low frequency band of a signal obtained by such a decoding process (hereinafter, referred to as a decoded signal) is replaced with the low frequency band of an input transmission signal. Rather, the replacement can be expected to increase the vertical resolution and improve the dynamic resolution, and it has already been proposed to replace the low band (Japanese Patent Application Laid-Open No. Sho 62-172).
No. 875).

[Problem to be Solved by the Invention] When an input transmission signal is compared with a decoded signal,
The transmission signal has more noise components than the decoded signal because the decoding processing (including the noise reduction processing) is not performed.

As described above, various effects can be obtained by the low-frequency replacement, but when the input transmission signal is replaced with an input transmission signal containing a large amount of noise components, the quality of the reproduced image may be deteriorated. Since the low-frequency noise component becomes a wide noise from the display image, it is conspicuous, and the image quality is easily deteriorated as described above.

The present invention has been made in view of the above points,
An object of the present invention is to provide a low-frequency replacement circuit that can obtain good image quality even when a low-frequency noise component of an input transmission signal is included.

[Means for Solving the Problems] In order to solve the problems, in the first aspect of the present invention, decoding obtained by performing decoding processing on a multiplexed sub-sample transmission signal that does not include a folded component between frames in a low frequency band. A low-band replacement circuit that replaces a low-band of the signal with a low-band of the multiplexed sub-sample transmission signal that has not been decoded; and a noise detection unit that detects at least a low-band noise amount of the multiplexed sub-sample transmission signal. Replacement varying means for varying the replacement ratio between the low frequency of the decoded signal and the low frequency of the multiplexed subsample transmission signal according to the amount of noise is provided.

In the second aspect of the present invention, the low frequency band of the decoded signal obtained by decoding the multiplexed sub-sample transmission signal that does not include the aliasing component between frames in the low frequency band is converted to the multiplexed sub-sample not decoded. In a low-frequency replacement circuit that replaces a low frequency band of a transmission signal, a noise reduction unit that performs a coring process for compressing a low-level low-frequency portion of a multiplexed sub-sample transmission signal to be replaced and reducing a noise component is provided.

According to a third aspect of the present invention, the noise reduction means in the second aspect of the present invention varies the amount of compression in accordance with the amount of noise detected by the newly provided noise detection means.

A fourth aspect of the present invention includes both a component according to the first aspect of the present invention and a component according to the second aspect of the present invention.

According to a fifth aspect of the present invention, the noise reduction unit according to the fourth aspect of the present invention varies the amount of compression in accordance with the amount of noise detected by the noise detection unit.

[Operation] In the case where many noise components are mixed in the low frequency band of the multiplexed sub-sample transmission signal which is the signal to be replaced, the image quality is greatly deteriorated by the replacement.

In that case, the replacement may be performed to such an extent that the image quality does not deteriorate due to the replacement. At this time, if the effect of the replacement is also expected, it is preferable that the replacement is made large when the noise component is small, and it is replaced slightly when the noise component is large. Therefore, in the first aspect of the present invention, the noise detection means detects at least the low-frequency noise amount of the multiplexed sub-sample transmission signal, and the replacement variable means detects the low-frequency noise of the decoded signal according to the detected noise amount.
The rate of replacement of the multiplex sub-sample transmission signal with the low band is varied.

Since it is required to suppress image quality degradation due to a large amount of noise components mixed in, it is only necessary to reduce the noise components in order to satisfy the requirement. Therefore,
According to the second aspect of the present invention, a noise reduction unit is provided to compress a low-level low-level portion of a multiplexed sub-sample transmission signal to be replaced to reduce a noise component.

If the compression processing is performed when the noise component is small, the original signal portion may be degraded. Therefore, it is preferable to control the noise reduction processing according to the noise amount. Third
The present invention combines the configuration of the second present invention with variable control based on the amount of noise.

The basic inventions for suppressing the image quality deterioration due to the mixing of many noise components are the above-described first and second (third) inventions. The effect can be expected. The fourth and fifth aspects of the present invention are a combination of these aspects.

EXAMPLES Hereinafter, first to fifth examples of the present invention will be sequentially described in detail with reference to the drawings.

First Embodiment First, a first embodiment will be described with reference to FIG.

In FIG. 1, an input multiplexed subsample transmission signal is supplied to a decoding processing unit 1. Decoding processing unit 1
Performs decoding processing such as inter-frame interpolation processing, inter-field interpolation processing, field interpolation, and noise reduction processing (for details, see Ninomiya et al., "Hi-Vision Satellite Transmission System-MUSE-", Magazine, Vol. 4
2, No. 5 (1988) and others).

The decoded signal is provided to the low-frequency replacement unit 2. The low-frequency replacement unit 2 is provided as a signal to be replaced by the input multiplex sub-sample transmission signal. In the low-frequency replacement unit 2, a difference signal between the multiplexed sub-sample transmission signal and the decoded signal is obtained by the subtractor 3, and the difference signal is multiplied by a coefficient through the variable coefficient unit 4. Only the band component (for example, 0 to 4 MHz) is waved, and finally, the wave signal and the decoded signal are added by the adder 6 to replace the low band.

The fact that the replacement is performed by such an arithmetic processing will be described in detail. Considering the low band of the multiplexed sub-sampled transmission signal in consideration of passing through the low-pass filter unit 5, the low band passes through the subtractor 3, is multiplied by the coefficient unit 4 and added to the decoded signal by the adder 6. Will be done.
On the other hand, considering the low-pass of the decoded signal in consideration of passing through the low-pass filter section 5, the low-pass passes through the subtractor 3, the polarity is inverted, is multiplied by the coefficient unit 4, and is multiplied by the adder 6. Such addition substantially means subtraction since it will be added to the decoded signal and the polarity is reversed.

That is, the low band of the multiplexed sub-sample transmission signal is multiplied by a coefficient and added to the decoded signal, and the low band of the decoded signal is multiplied by the coefficient and subtracted from the decoded signal. Will be.

In the case of the first embodiment, the noise detector 7 generates a control signal for the variable coefficient unit 4. The noise detection unit 7 is provided with the input multiplexed sub-sample transmission signal, and detects a noise amount of the transmission signal. A smaller coefficient is output as the amount of noise increases, and a larger coefficient is output as the amount of noise decreases. In other words, the greater the amount of noise, the smaller the ratio of replacement with the input multiplexed subsample transmission signal and the higher the ratio of the decoded signal.The smaller the noise amount, the more the input multiplexed subsample transmission signal. The rate of replacement is increased and the rate of decoded signals is reduced.

Controlling the replacement ratio in accordance with the amount of noise in this way comprehensively considers the improvement in image quality due to the improvement in vertical resolution and dynamic resolution due to replacement, and the reduction in image quality due to the conspicuousness of noise portions due to replacement. This is because the best image quality was obtained.

Therefore, according to the first embodiment, when the amount of the noise component is large, the replacement ratio is reduced.
Even if the transmission signal contains a low-frequency noise component, the image quality based on the low-frequency replacement signal can be maintained in a good state.

However, it is conceivable to selectively control whether or not to perform low-frequency replacement according to the noise amount. However, in practice, since the noise amount changes in an analog manner, it is not sufficient to improve the image quality. is there.

Second Embodiment Next, a second embodiment will be described with reference to FIG.

In FIG. 2, the input multiplex sub-sample transmission signal is provided to a decoding processing unit 11. Decoding processing unit 11
Performs decoding processing such as inter-frame interpolation processing, inter-field interpolation processing, field interpolation, and noise reduction processing, and supplies a decoded signal to the low-frequency replacement unit 12.

An input multiplexed sub-sample transmission signal is provided to the low-frequency replacement unit 12. In the low-frequency replacement unit 12, a subtraction unit 13 obtains a difference signal between the multiplexed sub-sample transmission signal and the decoded signal, and the difference signal is compressed through the coring processing unit 14, and only a low-level portion is compressed. Only the low-frequency component is waved by the low-pass filter unit 15, and finally, the wave signal and the decoded signal are added by the adder 16 to replace the low frequency component.

The reason why the coring processing unit 14 is provided is that noise is reduced by compressing a low-level portion, and low-frequency conversion in which the noise of the input multiplex sub-sample transmission signal is replaced even when the noise is large. This is because it is intended to reduce the noise in the signal and to prevent the image quality from being deteriorated due to the noise while maintaining the effects such as improvement of the vertical resolution and the dynamic resolution by the replacement.

Thus, according to the second embodiment, it is possible to improve the image quality as compared with the related art.

Third Embodiment Next, a third embodiment will be described with reference to FIG.
The third embodiment differs from the second embodiment in that the amount of coring processing (the amount of noise reduction) is varied depending on the amount of noise of the input multiplexed sub-sample transmission signal.

In FIG. 3, the input multiplexed sub-sample transmission signal is provided to a decoding processing unit 21, which performs a decoding process, and the decoded signal is provided to a low band replacement unit 22.

An input multiplexed sub-sample transmission signal is provided to the low band replacement section 22. In the low-frequency replacement unit 22, a difference signal between the multiplexed sub-sample transmission signal and the decoded signal is obtained by the subtractor 23, and this difference signal is compressed through the variable coring processing unit 24, and only a low-level portion is compressed. Then, only the low-frequency component is waved by the low-pass filter 25, and finally, the wave signal and the decoded signal are added by the adder 26 to replace the low-frequency component.

In the case of the third embodiment, a noise detector 27 generates a control signal for the variable coring processor 24. This noise detection unit 27 detects the noise amount of the input multiplexed sub-sample transmission signal. A control signal is output so that the larger the amount of noise, the larger the coring process, and the smaller the amount of noise, the smaller the coring process.

The reason why the amount of coring processing is controlled in accordance with the amount of noise in this way is that when the amount of noise is small, if the coring processing is performed large, the reduction other than the noise component also increases, and the image quality is improved by replacement. This is because the effect may be reduced.

Thus, according to the third embodiment, the image quality can be improved as compared with the related art.

Fourth Embodiment Next, a fourth embodiment will be described with reference to FIG.
The fourth embodiment differs from the first embodiment in that a coring processing unit is interposed between the variable coefficient unit and the low-pass filter unit.

In FIG. 4, the input multiplexed subsample transmission signal is
After being decoded by the decoding processing unit 31, it is provided to the low-frequency replacement unit 32.

In the low-frequency replacement unit 32, a subtractor 33 obtains a difference signal between the multiplexed sub-sample transmission signal and the decoded signal. The variable coefficient unit multiplies the difference signal by a coefficient corresponding to the noise detection signal from the noise detection unit. Thereafter, the coring processing unit 36 performs a coring process, the low-pass filter unit 37 passes only the low-frequency component, and the adder 38 adds the wave signal and the decoded signal, thereby replacing the low frequency band.

In this embodiment, the variable coefficient unit 34 whose coefficient is controlled by the noise amount is provided for the same reason as in the first embodiment, and the coring processing unit 36 is provided in the second embodiment. For the same reason as in the embodiment.

Thus, according to the fourth embodiment, the image quality can be improved as compared with the related art.

Fifth Embodiment Next, a fifth embodiment will be described with reference to FIG.
The fifth embodiment differs from the fourth embodiment only in that the coring process is also varied depending on the amount of noise. The reason why the coring process is varied depending on the amount of noise is the same as in the third embodiment.

In FIG. 5, the input multiplexed subsample transmission signal is:
After being decoded by the decode signal unit 41, the decoded signal is supplied to the low band replacement unit 42.

In the low-frequency replacement unit 42, a subtractor 43 obtains a difference signal between the multiplexed sub-sample transmission signal and the decoded signal. The variable coefficient unit 44 multiplies the difference signal by a coefficient corresponding to the noise detection signal from the noise detection unit 45. Thereafter, the coring processing unit 46 performs a coring process according to the noise detection signal from the noise detection unit 45, the low pal filter unit 47 passes only the low frequency component, and the adder 48 outputs the wave signal and the decode signal. , Which replaces the low end.

According to the fifth embodiment as well, image quality can be improved as compared with the related art.

Other Embodiments (1) In the above-described embodiment, the detection of the noise amount of the input multiplexed sub-sampled transmission signal has been described. However, at least the noise amount of the low band which is the frequency component to be replaced may be detected. good. The noise detection unit may use an existing element in addition to being provided as an independent component. For example, a circuit for performing a noise reduction process may be used.

(2) The present invention can be widely applied not only to a MUSE decoder but also to a reproduction device for a multiplexed sub-sampled transmission signal.

(3) The position of the low-pass filter unit is not limited to a stage subsequent to the coefficient unit and the coring processing unit, and may be provided at a position preceding the stage.

[Effects of the Invention] As described above, according to the present invention, a coefficient defining the replacement ratio is varied according to the amount of noise, and / or coring processing is performed to reduce noise of low-frequency components to be replaced. Therefore, even if the input transmission signal includes a low-frequency noise component, the effect of the low-frequency substitution can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a low band replacement circuit according to the present invention, FIG. 2 is a block diagram of a second embodiment of the present invention, and FIG. 3 is a block diagram of a third embodiment of the present invention. FIG. 4 is a block diagram of a fourth embodiment of the present invention, and FIG. 5 is a block diagram of a fifth embodiment of the present invention. 1, 11... Decoding processing section, 2, 12.
3, 13 subtractor, 4 variable coefficient unit, 5, 15 low-pass filter unit, 6, 16 adder, 7 noise detection unit, 14 coring processing unit.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuichi Ninomiya 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside Japan Broadcasting Corporation Broadcasting Research Institute (72) Inventor Toshiro Omura 2-2-1 Jinnan, Shibuya-ku, Tokyo Examiner in the Japan Broadcasting Corporation Broadcasting Center Seiichi Tamura (58) Field surveyed (Int. Cl. ⁶ , DB name) H04N 7/00

Claims (5)

(57) [Claims] 1. A low frequency band of a decoded signal obtained by decoding a multiplexed subsample transmission signal that does not include a folded component between frames in a low frequency band. A low-frequency replacement circuit that replaces a low-frequency band of the decoded signal with at least a low-frequency noise amount of the multiplexed sub-sampled transmission signal; A low-frequency replacement circuit comprising: a replacement variable unit that varies a replacement ratio of a sample transmission signal with a low frequency. 2. The low frequency band of a decoded signal obtained by decoding a multiplexed sub-sampled transmission signal that does not include aliasing components between frames in the low frequency band. A low-frequency replacement circuit that replaces a low-frequency portion of the multiplexed sub-sampled transmission signal with a noise reduction unit that performs a coring process for reducing a noise component by compressing a low-level portion of the low frequency of the transmission signal. Range replacement circuit. 3. A noise detecting means for detecting at least a low-frequency noise amount of the multiplexed sub-sample transmission signal, wherein the noise reducing means varies a compression amount according to the detected noise amount. The low-frequency replacement circuit according to claim 2, wherein 4. The apparatus according to claim 1, further comprising noise reduction means for performing coring processing for compressing a low-level low-frequency portion of the multiplexed sub-sample transmission signal to be replaced to reduce noise components. 2. The low-frequency replacement circuit according to 1. 5. The low-frequency replacement circuit according to claim 4, wherein said noise reduction means varies the amount of compression in accordance with the amount of noise detected by said noise detection means.