JP2856903B2 - 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.

[Prior Art] As a method of transmitting a television signal by band compression, there is a multiplex sub-sample transmission method using offset sampling between frames and fields, and a high-definition television proposed by the Japan Broadcasting Corporation. The one for signals is called the MUSE system. Therefore, a reproduction apparatus for a transmission signal in accordance with the MUSE system, that is, a MUSE decoder appropriately performs decoding processing such as inter-frame interpolation processing, inter-field interpolation processing, field interpolation, and noise reduction processing to appropriately execute 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, it is possible to increase the vertical resolution and improve the dynamic resolution by replacing the gas, and it has already been proposed to replace the low frequency band (JP-A-62-1728).
No. 75 gazette).

FIG. 3 shows such a conventional low-frequency replacement circuit 10.

In FIG. 3, an input multiplexed sub-sample transmission signal is provided to a decoding processing unit 1 via a non-linear de-emphasis processing unit 2. The decoding processing unit 1 performs decoding processing such as inter-frame interpolation processing, inter-field interpolation processing, field interpolation, and noise reduction processing.

The decoded signal is supplied to the low-frequency replacement circuit 10.
This low-pass replacement circuit 10 is supplied as a signal to be replaced by the input multiplex sub-sample transmission signal. In the low-frequency replacement circuit 10, a difference signal between the multiplexed sub-sample transmission signal and the decoded signal is obtained by the subtractor 11, and this difference signal is converted by the replacement amount control unit 12 into one of, for example, one of five-stage coefficients. After that, only the low-frequency component (for example, 0 to 4 MHz) is waved by the low-pass filter unit 13, and finally, the wave signal and the decoded signal are added by the adder 14, and the low frequency band is replaced.

The control signal for the replacement amount control unit 12 is generated by the non-linear edge detection unit 15. In the MUSE method, when a non-linear edge fasis filter is used to lower the required C / N, high frequency components in the horizontal direction are lifted. The non-linear edge detection unit 15 is provided with the multiplexed sub-sample transmission signal before being input to the non-linear de-emphasis processing unit 2, and detects the non-linear edge amount of this transmission signal. If the amount of detection is small, it is determined that there is a low-frequency signal, and processing is performed with a large coefficient. To control.

[Problem to be Solved by the Invention] According to the conventional low-frequency replacement circuit, the resolution is improved, but there are the following problems.

The multiplexed subsample transmission signal, which is a replacement signal, has not been subjected to interpolation processing, noise reduction processing, or noise coring processing, and therefore has a poor S / N ratio compared to the decoded signal subjected to these processings It will be.

In addition, although the improvement of the moving image is recognized by performing the low-frequency replacement, the replacement is also performed for signals that do not require resolution in the vertical direction, and the effect of improving the vertical resolution is small,
The S / N ratio will deteriorate.

The present invention has been made in view of the above points,
It is an object of the present invention to provide a low-frequency replacement circuit that can perform the replacement process on a portion where the effect of the replacement is great, and that also has a good low-frequency S / N ratio after the replacement.

[Means for Solving the Problem] In order to solve such a problem, in the present invention, a decoding signal obtained by decoding a multiplexed subsample transmission signal that does not include a regression component between frames in a low frequency band is obtained. A low-frequency replacement circuit that replaces the low frequency with the low frequency of the multiplexed sub-sampled transmission signal that has not been decoded; a vertical edge detection unit that detects a vertical edge in the decoded signal; There is provided a replacement amount changing means for changing a replacement ratio between a low band of the decoded signal and a low band of the multiplexed sub-sample transmission signal.

Here, it is preferable to provide noise coring processing means for executing noise coring processing on the decoded signal and supplying the processed decoded signal to the vertical edge detecting means.

[Operation] The present invention has been made by paying attention to the fact that a portion where the effect of the low-frequency replacement is large is a vertical edge portion. The vertical edge detecting means detects a vertical edge in the decoded signal, and the replacement amount variable means. The ratio of replacement between the low band of the decoded signal and the low band of the multiplexed sub-sampled transmission signal is varied in accordance with the detected vertical edge amount. Here, the reason why the vertical edge is detected from the decoded signal is to effectively increase the vertical resolution.

In order to prevent a noise component from being erroneously detected as a vertical edge, noise coring processing means for executing a noise coring process on the decoded signal and supplying the decoded signal to the vertical edge detection means is provided. Is preferred.

Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the first embodiment,
The same or corresponding parts as those in FIG. 3 are denoted by the same reference numerals.

The low-frequency replacement circuit 20 according to this embodiment also has a replacement amount control, and the basic configuration of the replacement is the same as the conventional one.

That is, the input multiplexed sub-sample transmission signal is provided to the decoding processing unit 1 and subjected to decoding processing such as inter-frame interpolation processing, inter-field interpolation processing, field interpolation and noise reduction processing, and then subtraction. The difference from the multiplexed sub-sampled transmission signal inputted by the subtracter 11 is obtained as a subtracted input to the subtractor 11, and the difference signal is transmitted through the switching amount controller 12 to any one of, for example, five-stage coefficients. After that, only the low-frequency component (for example, 0 to 4 MHz) is waved by the low-pass filter unit 13, and finally, the wave signal and the decoded signal are added by the adder 14 to replace the low frequency component.

However, this embodiment is different from the conventional one in the control configuration of the replacement amount. That is, the configuration for providing a control signal to the replacement amount control unit 12 is different from the conventional configuration. The decode signal from the decode processing unit 1 is given to the vertical edge detection unit 23. The vertical edge detection unit 23 detects a vertical edge in the input decoded signal, and according to the detected amount,
The control signal is provided to the replacement control unit 12 such that the larger the detection amount is, the larger the replacement is.

That is, in the first embodiment, the vertical edge of the decoded signal is detected, and when the vertical edge is detected, the reduction of the decoded signal is replaced with the low frequency of the input multiplex sub-sample transmission signal in accordance with the edge amount. I have to.

Therefore, according to the above-described first embodiment, since the replacement is performed on the vertical edge portion where high resolution is required, the overall resolution can be improved.

FIG. 2 shows a second embodiment of the present invention, and portions corresponding to those in FIG. 1 are denoted by the same reference numerals.

The second embodiment differs from the first embodiment in the control structure of the replacement amount. That is, the configuration for controlling the replacement amount in the second embodiment includes the noise coring processing unit 21 and the noise level detection unit 22 in addition to the vertical edge detection unit 23.

The decoded signal is supplied from the decode processing unit 1 to the noise coring processing unit 21. The noise level detection unit 22 provided in association with the noise coring processing unit 21 detects the noise level of the decoded signal and provides the detection signal to the noise scoring processing unit 21. For example, the noise level detection unit 22 detects a noise amount by integrating a flat portion of a horizontal scanning line including a frame pulse in a decode signal. Noise coring processor 21
Performs a noise coring process according to the amount of noise detected on the decoded signal, and supplies the decoded signal whose noise component has been reduced by the coring process to the vertical edge detection unit 23.

Here, the noise coring processing unit 21 and the noise level detection unit 22 are provided because the vertical edge detection unit 23
Prevents the noise component from being erroneously detected as a vertical edge.

The vertical edge detection unit 23 detects a vertical edge in the input decoded signal after the noise coring processing, and, in accordance with the detection amount, replaces the control signal such that the larger the detection amount is, the larger the replacement signal is. Give to.

Therefore, according to the above-described second embodiment, since the replacement is performed on the vertical edge portion where high resolution is required, the overall resolution can be improved. In this way, noise components are not mistakenly detected as vertical edges, so unnecessary parts are not replaced, and parts that can be replaced by transmission signals with a poor S / N ratio need to be truly replaced. And the overall S / N ratio can be improved as compared with the conventional case.

In the above-described embodiment, the present invention is applied to the low-frequency replacement circuit of the MUSE decoder. However, the present invention is widely applied to a band compression television signal receiving apparatus (decoder) having the low-frequency replacement circuit. Can be.

Further, in the above-described embodiment, the case where the vertical edge is detected and the replacement amount is controlled is described. However, the replacement amount control based on the detection of the non-linear edge may be used together.

[Effects of the Invention] As described above, according to the present invention, a vertical edge is detected from a decoded signal and the replacement amount is varied according to the detected amount of the vertical edge. Can be performed only when the improvement effect of the above is large, and a low-frequency replacement circuit that can improve the S / N ratio as a whole can be realized.

[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, and FIG. 2 is a second embodiment of the low band replacement circuit according to the present invention.
FIG. 3 is a block diagram showing a conventional circuit. 1 ... Decoding processing unit, 2 ... Non-linear de-emphasis processing unit, 11 ... Subtractor, 12 ... Replacement amount control unit,
13 low-pass filter section, 14 adder, 20 low-pass replacement circuit, 21 noise coring processing section, 22 noise level detection section, 23 vertical edge detection section.

Claims (2)

(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 substituting circuit for substituting an area, a vertical edge detecting means for detecting a vertical edge extending in a vertical direction in the decode signal; a low-frequency area of the decode signal according to the detected vertical edge amount; A low-frequency replacement circuit provided with replacement amount varying means for varying a replacement ratio of a transmission signal with a low frequency. 2. A noise coring unit according to claim 1, further comprising noise coring processing means for executing a noise coring process on the decoded signal and supplying the processed decoded signal to the vertical edge detecting means. Range replacement circuit.