JP2928597B2 - Receiver for band-compressed television signal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a band-compressed television signal receiving apparatus, and is applicable to, for example, a MUSE decoder.

[Prior Art] The baseband bandwidth of a high definition television signal is about 30
MHz, and it is necessary to compress the band to about 8 MHz in order to transmit this on one channel of the current satellite broadcast. The MUSE system exists as a system for transmitting a high-definition television signal in a band-compressed manner.

In this MUSE system, a band compression method as exemplified below is used. (1) The time axis of the color signal is compressed to 1/4 and multiplexed in the horizontal blanking period of the luminance signal.
(2) In a still region of an image, dot interlace by offset sampling between fields and between frames is used. (3) In the moving area of the image, dot interlace by offset between lines is used. (4) Deterioration of resolution during pan and tilt is kept to a minimum by motion compensation.

Therefore, in the receiving apparatus, a band expansion configuration corresponding to these band compression methods is required, and a configuration for suppressing a noise component mixed in the transmission system, a noise component generated through the compression / decompression processing, and the like is required.

As a configuration for suppressing noise components, a noise reduction circuit, a noise coring circuit, and the like are provided.
The present invention relates to a noise coring circuit.

FIG. 5 shows a conventional noise coring circuit provided in a moving area processing system for a luminance signal.

In FIG. 5, a television signal (a signal including a luminance signal and a chrominance signal in time sequence) subjected to field interpolation processing by a field interpolation circuit (not shown) in a moving area processing system of a luminance signal is referred to as the television signal. Noise coring circuit 10
Given to. The noise coring circuit 10 includes a low-pass filter circuit 11, a first subtraction circuit 12, a second subtraction circuit 13, and a noise coring amount setting circuit 14, and the television signal S1 outputs a low-pass filter circuit 11, a first subtraction circuit
12 and a second subtraction circuit 13.

The low-frequency component S2 filtered through the low-pass filter circuit 11 is given as a subtraction input to a first subtraction circuit 12, and thus the high-frequency component S3 of the television signal S1 including a noise component is also output from the subtraction circuit 12. can get. The high frequency component S3 is provided to the noise coring amount setting circuit 14. The noise coring amount setting circuit 14 extracts only the high-frequency component S3 whose level is equal to or less than a predetermined value, and supplies it to the second subtraction circuit 10 as a subtraction input. As a result, a signal is obtained from the subtraction circuit 13 in which components having a frequency equal to or higher than the predetermined frequency of the television signal S1 and the level of which is equal to or lower than the predetermined value are removed as a noise component. The signal is supplied to an adaptive mixing circuit (not shown) in the signal processing system and a field interpolation circuit (not shown) in the color signal processing system.

[Problem to be Solved by the Invention] As described above, a television signal in which a luminance signal and a chrominance signal appear in time sequence is input to the noise coring circuit 10, but the television signal supplied to the MUSE decoder is Are different in the encoding method of the luminance signal and the chrominance signal. That is, the encoding method of the chrominance signal has a characteristic that the aliasing component is included up to near the DC component, compared with the encoding method of the luminance signal.

Thus, despite the different noise components,
Conventionally, a luminance signal and a chrominance signal are processed with the same noise coring characteristics. As a result, the noise component of the color signal was more conspicuous than the luminance signal.

Increasing the amount of noise coring in order to solve such inconveniences can reduce noise components for color signals, but for luminance signals, the original components that are not noise components are also suppressed and image quality deteriorates. was there.

JP-A-2-96494 “Image signal processing circuit” receives a television signal in which a luminance signal, a time-compressed color difference signal and a synchronization signal are time-division multiplexed, and reduces noise by a noise reduction circuit. There is disclosed a circuit in which, when processing is performed, the coefficient of a coefficient unit that affects the amount of noise reduction provided commonly to a luminance signal and a chrominance signal is separately controlled for the luminance signal and the chrominance signal. However, this circuit only considers that the noise component superimposed on the transmission path differs between the luminance signal and the time-compressed chrominance signal, and performs only the cyclic noise reduction processing with the coefficient adapted to each signal. Moreover, a cyclic noise reduction circuit that multiplies a field difference signal by a coefficient and cyclically adds the input signal to the input signal is
As the noise reduction effect increases, the occurrence of afterimages is inevitable,
Since a frame memory for storing image data for four fields is still indispensable, the circuit configuration is very complicated.
In addition to the NR control signal time-division multiplexed to the television signal, a noise detection circuit for detecting this transmission noise is required, and the outputs of the NR control signal extraction circuit and the noise detection circuit are logically processed in a logical circuit, and the logical Since the coefficient of the coefficient unit is switched based on the processing output, there is a problem that further complication of the entire circuit cannot be avoided.

The present invention has been made in view of the above points,
An object of the present invention is to provide a band-compressed television signal receiving apparatus capable of performing appropriate noise coring processing on both a chrominance signal and a luminance signal.

[Means for Solving the Problems] In order to solve the problems, in the present invention, the color signal is compressed on the time axis and multiplexed in the horizontal blanking period of the luminance signal, and the time division multiplexed signal is subjected to multiplex sampling encoding. A band interpolation television signal, and a field interpolation circuit for interpolating the luminance signal included in the band compression television signal in a field, and a field interpolation circuit disposed downstream of the field interpolation circuit. High-frequency component extraction means for extracting high-frequency components included in the output of the field interpolation circuit; and a high-frequency component extracted by the high-frequency component extraction means for determining different threshold values for the luminance signal period and the chrominance signal period. Sorted into criteria
Noise coring processing means for extracting only a component less than the threshold value and subtracting the extracted component from the output.

[Operation] In the present invention, the noise coring processing means provided at the subsequent stage of the field interpolation circuit for the luminance signal performs processing with different noise coring characteristics between the luminance signal period and the chrominance signal period. As a result, the noise coring characteristic for the luminance signal and the noise core rig characteristic for the chrominance signal can be separately set to be appropriate, and the image quality can be improved as compared with the conventional art.

Hereinafter, a first embodiment in which the present invention is applied to a MUSE decoder will be described in detail with reference to the drawings.

FIG. 1 shows a noise coring circuit of the first embodiment. In the figure, a television signal (a signal including a luminance signal and a chrominance signal in time sequence) S10 subjected to intra-field insertion processing by a field interpolation circuit (not shown) in a luminance signal moving area processing system is the signal. It is provided to the noise coring circuit 20.

The noise coring circuit 20 includes a low-pass filter circuit 21, a first subtraction circuit 22, a second subtraction circuit 23, a noise coring amount setting circuit 24 for a luminance signal, a noise coring amount setting circuit 25 for a chrominance signal, first and second signals. And two switch circuits 26 and 27, and a synchronization separation timing generation circuit 28. Note that the synchronization separation timing generation circuit 28 is not used only for the noise coring circuit 20, but for the entire MUSE decoder.

Television signal S10 from field interpolation circuit
Is a low-pass filter circuit 21, a subtraction circuit 22, and a subtraction circuit
Given to 23.

The low-frequency component S11 of the television signal S10 filtered through the low-pass filter circuit 21 is provided to a first subtraction circuit 22 as a subtraction input, and thus the subtraction circuit 22
, A high-frequency component S12 including a noise component is obtained.

This high frequency component S12 is provided to a switch circuit 26 having a one-input two-output configuration. This switch circuit 26 is a switch circuit
The switching operation is performed in conjunction with 27, and a selection control signal Y / C is given to these switch circuits 26 and 27 from a synchronization separation timing generation circuit 28.

FIG. 2 shows the positions of the color signal (color difference signal) and the luminance signal on the time axis. The synchronization separation timing generation circuit 28 switches the switching circuits 26 and 27 at the timing of the luminance signal.
Selects the luminance signal noise coring amount setting circuit 24,
The switch circuits 26 and 27 provide a selection control signal Y / C to the switch circuits 26 and 27 so that the switch circuits 26 and 27 select the color signal noise coring amount setting circuit 25 at the timing of the color signal.

Noise coring amount setting circuit for luminance signal and color signal
Both 24 and 25 take out only the high-frequency component S12 input through the switch circuit 26 and have a level equal to or lower than a predetermined value, and output the second subtraction circuit 23 through the switch circuit 27.
As a subtraction input. Here, the luminance signal noise coring amount setting circuit 24 has a predetermined value set for the noise coring amount suitable for the luminance signal, and the color signal noise coring amount setting circuit 25 has the predetermined value for the color signal noise coring amount. Is set. For example, the color signal noise coring amount is set large.

From the subtraction circuit 23 to which the high-frequency component S13 whose level is equal to or lower than the predetermined value is given, a signal is obtained in which the component whose level is equal to or lower than the predetermined value is removed as a noise component, and this is the output signal S14 of the noise coring circuit 20. Are supplied to an adaptive mixing circuit (not shown) in the luminance signal processing system and a field interpolation circuit (not shown) in the color signal processing system.

Therefore, according to the first embodiment, since the noise coring process can be performed by setting the optimum noise coring amount for each of the color signal and the luminance signal, the image quality can be improved as compared with the related art.

FIG. 3 shows a second embodiment of the present invention. In the second embodiment, a circuit 21Y for a luminance signal and a circuit 21C for a color signal are provided as low-pass filter circuits,
A switch circuit 29 for selecting the output by a selection control signal Y / C is provided so that the frequency components for noise coring processing are different between the luminance signal and the chrominance signal.

According to the second embodiment, since the frequency components to be subjected to the noise coring process are also made different for the luminance signal and the chrominance signal, the configuration becomes complicated, but the image quality can be improved more than the first embodiment. FIG. 4 shows a third embodiment of the present invention. In the third embodiment, a noise coring circuit 31 performs a noise coring process on a television signal supplied from a field interpolation circuit 30 of a luminance signal processing system irrespective of a luminance signal and a chrominance signal. The output is applied to the adaptive mixing circuit 32 of the luminance signal processing system and to the field interpolation circuit 34 of the color signal processing system via the second noise coring circuit 33 so that the noise coring for the color signal and the luminance signal is The amount was changed.

In the third embodiment, the first noise coring circuit 31 and the second noise coring circuit 33 constitute noise coring processing means, and set the optimum noise coring amounts for the color signal and the luminance signal. Since the noise coring process can be performed by using the image processing, the image quality can be improved as compared with the related art.

In the above embodiment, the present invention is applied to the MUSE decoder. However, the present invention is not limited to this, and may be applied to other devices using the same encoding method. Can also be applied. For example, at the moment,
Although the U.S. standard for high-definition television signals has not been clearly defined, it is thought that when applying it to satellite broadcasting, an encoding system similar to the MUSE system will be adopted. The present invention can be applied to a signal receiving device.

[Effects of the Invention] As described above, according to the present invention, a color compression signal is time-axis-compressed, multiplexed in a horizontal blanking period of a luminance signal, and the time-division multiplexed signal is sampled and coded for band compression television. A signal is received, and a high-frequency component is extracted from an output of a field interpolation circuit that interpolates a luminance signal included in the received signal into a field, and is selected based on different threshold values in a luminance signal period and a chrominance signal period. Since only the components less than the threshold value are extracted and subtracted from the output, when the luminance signal and the chrominance signal included in the time-division multiplexed television signal are compared, the time axis during the horizontal blanking period is Although the compressed color signal contains aliasing components close to the DC component, the noise component is more visible than the luminance signal by applying different noise coring processing to the luminance signal and the color signal. Appropriate noise coring processing can be performed on the standing color signal, and thus, for example, the noise coring amount can be reduced even if the noise component for the color signal can be reduced because the amount of noise coring is uniformly increased as in the conventional case. Does not suppress the original components that are not noise components, does not cause image quality degradation, and has excellent effects such as being able to perform optimal noise coring processing focusing on the characteristics of the luminance signal and the color signal. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a band-compressed television signal receiving apparatus according to the present invention. FIG. 2 is a format diagram showing a positional relationship between a luminance signal and a chrominance signal on a time axis. FIG. 4 is a block diagram showing a second embodiment of the present invention. FIG. 4 is a block diagram showing a third embodiment of the present invention.
FIG. 5 is a block diagram showing a conventional apparatus. 20 noise coring circuit 21 low-pass filter circuit 22, 23 subtraction circuit 24 noise coring amount setting circuit for luminance signal 25 noise coring amount setting circuit for color signal 26, 27 switch circuit 28 ... Synchronous separation timing generator

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 11/00-11/24 H04N 7/00-7/015

Claims (1)

(57) [Claims] 1. A band-compressed television signal obtained by time-compressing a chrominance signal, multiplexing it in a horizontal blanking period of a luminance signal, and multiplex-sampling the time-division multiplexed signal. A field interpolation circuit for interpolating the luminance signal included in the signal in a field, and a high frequency component included in an output of the field interpolation circuit, which is disposed at a subsequent stage of the field interpolation circuit. High-frequency component extraction means, and high-frequency components extracted by the high-frequency component extraction means are selected based on different threshold values in a luminance signal period and a chrominance signal period, and only components that do not satisfy the threshold value are extracted. And a noise coring processing means for subtracting the output from the output.