JPH0549011A - High definition television signal decoder - Google Patents

Abstract

PURPOSE:To attain high performance and to reduce the cost by simplifying the circuit configuration for low frequency replacement and improving effectively the replacement with the low frequency replacement. CONSTITUTION:A still picture processing circuit 11 decodes a still picture of a MUSE signal. A moving picture processing circuit 12 is provided with a two-dimension interpolation filter 15 and a sample rate conversion circuit 16. The moving picture processing circuit 12 decodes a moving picture of the MUSE signal. The two-dimension interpolation filter 15 makes the filter characteristic in the vertical direction broad. An output of the two-dimension interpolation filter 15 is subject to rate conversion by a sample rate conversion circuit 16 and a motion picture decode output of the moving picture processing circuit 12 is obtained. A mixer 13 mixes a still picture decode output and a moving picture decode output and gives the result to a low frequency replacement circuit 14. The low frequency replacement circuit 14 replaces a low frequency of the output of the mixer 13 with a low frequency of the moving picture decode output from the moving picture processing circuit 13 and outputs the result.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to, for example, MUSE (mu
The present invention relates to a high-definition television signal decoder for demodulating a high-definition television signal such as an ltiple sub-nyquist sampling encoding) system, and particularly to a high-definition television signal decoder with improved low frequency replacement processing.

[0002]

BACKGROUND OF THE INVENTION High definition television signals such as MUSE.
When decoding the signal, so-called low frequency replacement processing is performed. The low-pass replacement processing is a replacement of a low-pass signal of 4 MHz or less that does not include aliasing of a MUSE signal with a low-pass signal of a decoded signal, that is, low-pass replacement, which occurs during still image decoding processing. This is a process for reducing interference due to a decrease in vertical resolution and a motion detection error.

In a conventional MUSE decoder, a still image decoded signal and a moving image decoded signal are mixed according to motion detection information and then replaced with the low frequency component of the MUSE signal before decoding. Was there.

An example of such a conventional MUSE decoder is shown in FIG. In FIG. 2, a terminal T receives a MUSE signal (in this case, a 16.2 MHz rate MUSE digital signal). The MUSE signal is given to a still image processing circuit 1 for still image decoding, a moving image processing circuit 2 for moving image decoding, and a sub-sampling processing circuit 3 for sub-sampling. The still image processing circuit 1 performs still image decoding of the MUSE signal, that is, decoding of the MUSE signal suitable for the still image information component. The video processing circuit 2 decodes video of MUSE signal,
That is, the MUSE signal suitable for the moving image information component is decoded. The mixer (MIX) 4 mixes the output of the still image processing circuit 1 and the output of the moving image processing circuit 2 according to the separately detected motion detection information, and outputs it as a 48.6 MHz rate. The output of the mixer 4 is supplied to the low frequency substituting circuit 5 which performs the above low frequency substituting processing. In this case, the low band signal used for the low band replacement processing in the low band replacement circuit 5 is obtained from the MUSE digital signal input to the terminal T before being decoded.

That is, the MUSE digital signal input to the terminal T is sub-sampled by the sub-sampling processing circuit 3, and then interpolated by the interpolating low-pass filter 6 to obtain data of 32.4 MHz rate. The conversion circuit 7 converts the output data of the mixer 4 into the same data of 48.6 MHz rate. As described above, the low-frequency signal obtained from the MUSE signal through the sub-sample processing circuit 3-interpolation low-pass filter 6-data rate conversion circuit 7 is converted into the low-frequency signal output from the mixer 4 by the low-frequency replacement circuit 5. And output it.

As another example of the conventional MUSE decoder, Japanese Patent Laid-Open No. 1-318391 discloses S / N.
In order to improve the (signal-to-noise ratio), the low-pass signal for low-pass replacement is used as the signal after noise reduction processing, and this signal is set to 2H from the interpolation filter in the moving image processing circuit.
(H is a horizontal scanning period) It is shown that the signal is extracted and used as a delayed signal.

[0007]

However, the low-frequency replacement processing in the MUSE decoder shown in FIG. 2 has the following problems. (1) The circuit configuration becomes complicated. That is, in order to obtain the replacement low-frequency signal used in the low-frequency replacement circuit, the 16.2 MHz rate signal before the still image decoding and the moving image decoding is delayed, and after the sub-sampling phase processing is performed by the sub-sampling processing circuit 3. Furthermore, since it is necessary to convert to 48.6 MHz, the circuit configuration of the MUSE decoder becomes complicated.

(2) A folding component may occur as a side effect of low frequency replacement. That is, due to the non-linear processing of the transmission system or the like, the aliasing component may enter the low frequency band of 4 MHz or less, and in such a case, the aliasing occurs in the output due to the low frequency band replacement processing. To deal with this, it is possible to take measures such as detecting the non-linear edge portion of the replacement signal and prohibiting replacement, but this also fails to obtain sufficient results, especially for the diagonal component. There is almost no effect on folding back.

Further, as disclosed in Japanese Patent Laid-Open No. 1-318391, even if a low-pass signal for low-pass replacement is taken out from an interpolation filter in a moving image processing circuit after noise reduction processing, The problems mentioned above still remain unsolved.

The present invention has been made in view of the above circumstances, and can simplify the circuit configuration for low-frequency replacement and effectively improve the folding back due to low-frequency replacement. It is an object of the present invention to provide a high-definition television signal decoder which is capable of high performance and is low in cost.

[0011]

A high-definition television signal decoder according to the present invention is a still picture processing system for decoding a high-definition television signal as a still picture, and a high-definition television signal for moving picture decoding. Video processing system,
Mixing means for mixing the signals decoded by the still image processing system and the moving image processing system according to the motion detection information, and a low-frequency signal that does not include a folding component in the low-frequency signal of the signals mixed by the mixing means. In a high-definition television signal decoder provided with a low-pass replacement means for replacing a moving image, the moving image processing system has a two-dimensional filter for moving image processing in which a vertical characteristic is relatively broad, and The replacement means is characterized in that the low frequency component of the signal decoded by the moving image processing system is used as a low frequency signal for low frequency replacement.

[0012]

In the high-definition television signal decoder of the present invention, the signal obtained as a result of the moving picture decoding processing is not used as the low-frequency signal for low-frequency replacement instead of the signal before the still picture and the moving picture decoding. Since it is used as a low-pass signal for low-pass replacement, the circuit configuration for low-pass replacement can be simplified, and the aliasing due to low-pass replacement can be effectively improved.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a MUSE decoder which is a high definition television signal decoder according to an embodiment of the present invention. The MUSE decoder shown in FIG. 1 is composed of a still image processing circuit 11, a moving image processing circuit 12, a mixer 13, and a low frequency replacement circuit 14. The still image processing circuit 11, the moving image processing circuit 12, the mixer 13, and the low frequency substituting circuit 14 correspond to the still image processing circuit 1, the moving image processing circuit 2, the mixer 4, and the low frequency substituting circuit 5 in FIG. 2, respectively. Correspond.

The still image processing circuit 11 is similar to the still image processing circuit 1 of FIG. 2, and performs still image decoding of the MUSE signal (MUSE digital signal of 16.2 MHz rate) input to the terminal T. The still image decode output of the still image processing circuit 11 is given to the mixer 13.

The moving image processing circuit 12 has a two-dimensional interpolation filter 15 and a sample rate conversion circuit 16. The moving picture processing circuit 12 has substantially the same function as the moving picture processing circuit 2 of FIG. 1, and decodes the moving picture of the MUSE signal input to the terminal T. In this case, the two-dimensional interpolation filter 15
Makes the filter characteristics in the vertical direction considerably broader, as will be described later. The output of the two-dimensional interpolation filter 15 is 3
The signal has a 2.4 MHz rate, and this signal is converted into a signal having a rate of 48.6 MHz by the sample rate conversion circuit 16 and is given to the mixer 13 as a moving image decoding output of the moving image processing circuit 12.

The mixer 13 mixes the still image decoded output from the still image processing circuit 11 and the moving image decoded output from the sample rate conversion circuit 16 of the moving image processing circuit 12 according to the separately detected motion detection information. , To the low frequency replacement circuit 14.

The low frequency substituting circuit 14 is a mixer 13 in which a still image decoded output and a moving image decoded output are mixed.
The low band of the video decoding output from the video processing circuit 12 is replaced with the low band of the output of the above, and is output according to the replacement control signal described later. That is, the low frequency substituting circuit 14 obtains the low frequency signal used for the low frequency substituting processing from the video decoding output of the video processing circuit 12.

If there is no aliasing in the low frequency band, for example, 4 MHz or less, the decoded still image and moving image signals of 4 MHz or less are exactly the same, so that the mix by the mixer 13 is 4 MHz or more. It will be sufficient to perform only for the high frequency signal of. However, in reality, as described above, a folding component may occur even at 4 MHz or less due to non-linear processing of the transmission system. For this reason, the mixer 13 mixes the entire band in accordance with the motion detection information, and then the low band replacement circuit 14 adaptively replaces it. A replacement control signal for realizing this adaptive replacement is applied to the low-frequency replacement circuit 14, and the low-frequency replacement circuit 14 performs low-frequency replacement according to the replacement control signal. In the current system, the replacement control signal is obtained by detecting a non-linear edge of the signal with a non-linear de-emphasis circuit, expanding the width with a low-pass filter, and then converting the sample rate from 16.2 MHz to 48.6 MHz. ..

The characteristics of the two-dimensional interpolation filter 15 of the moving picture processing circuit 12, which is a two-dimensional filter of the moving picture processing system, will be described. Originally, in the field interpolation filter, the vertical resolution must be limited to 1/2 in order to remove the folding in the vertical direction, but in reality, the vertical direction has a relatively broad characteristic. No significant image quality deterioration occurs. This is because the vertical folding of the moving image portion is inconspicuous. Therefore, if low-pass replacement is performed by the signal subjected to the moving picture decoding process in the moving picture processing circuit 12 using the two-dimensional interpolation filter 15 having such a characteristic that is relatively broad in the vertical direction, interference at the time of motion detection error will occur. It is sufficiently effective not only for improving the vertical resolution, but also for improving the vertical resolution.

As described above, in this embodiment, the MUSE signal before decoding is not used as the low band signal for low band replacement, but the signal obtained from the moving image processing circuit 12 as a result of the moving image decoding process is used. It is used as a low band signal for low band replacement by the low band replacement circuit 14. That is, since the low frequency range of the video processed signal is used as it is,
A delay circuit, a sub-sample processing circuit, an LPF, a data rate conversion circuit, etc. are not required, and the circuit becomes simple. Also,
Since the signal from which the oblique aliasing component has been removed by the two-dimensional filter of the moving image processing system is used for low-pass replacement, aliasing is significantly improved.

The present invention is not limited to a MUSE signal decoder, but can be applied to any high-definition television signal decoder as long as it is a decoder for decoding a high-definition television signal having a substantially similar signal format. Can be applied.

[0022]

As described above, according to the present invention,
By using the signal obtained as a result of the video decoding process as the low-pass signal for low-pass replacement, instead of using the signal before decoding still images and moving images as the low-pass signal for low-pass replacement, (EN) Provided is a high-performance and low-cost high-definition television signal decoder capable of simplifying a circuit configuration for replacement and effectively improving folding due to replacement in a low frequency range. it can.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a MUSE decoder which is a high quality television signal decoder according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an example of a conventional MUSE decoder.

[Explanation of symbols]

11 ... Still image processing circuit, 12 ... Moving image processing circuit, 13 ... Mixer, 14 ... Low-pass replacement circuit, 15 ... Two-dimensional interpolation filter, 16 ... Sample rate conversion circuit.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04N 11/04 B 9187-5C 11/08 9187-5C

Claims (1)

[Claims] 1. A still image processing system for decoding a high-definition television signal as a still image, a moving image processing system for decoding the high-definition television signal as a moving image, and decoding by these still image processing system and moving image processing system. A mixing means for mixing the mixed signal according to the motion detection information, and a low-pass replacing means for replacing the low-frequency signal of the signal mixed by the mixing means with the low-frequency signal containing no folding component. In the high-definition television signal decoder, the moving image processing system has a two-dimensional filter for moving image processing in which the vertical characteristic is relatively broad, and the low-pass replacement section is a moving image decoding system by the moving image processing system. A high-definition television signal decoder, characterized in that the low-frequency component of the converted signal is used as a low-frequency signal for low-frequency replacement.