JPH01286688A - Low frequency band replacing circuit for muse decoder - Google Patents

Abstract

PURPOSE:To improve the picture quality of a still picture without adding an exclusive-use frame memory by diverting a frame memory for detecting the movement of a picture, which becomes unnecessary during a still display operation, to a frame memory to store the unprocessed signals of a still display picture. CONSTITUTION:When a command signal for the still display operation is given to an input terminal 12, the operation of a movement detecting circuit 5a is stopped, and a switch S1 to compose a switch 8c is switched to a lower side. Accompanying this, a movement detecting part 5 starts taking preprocessed video signals in a frame memory 5b. When the taking in of the signals is completed, preprocessed video signals for one frame taken in the memory 5b are repeatedly read in a frame cycle and supplied to a low frequency replacing device 8a. On the other hand, a loop is formed between the input and the output of a frame memory 4b of an inter-frame interpolating part 4, and the video signals for the frame taken in immediately after the command for the still display operation is generated are repeatedly read. As the result, the still picture, in which vertical resolution is improved by the replacement of the low frequency, is displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a low frequency replacement circuit for a MUSE decoder installed in a MUSE television receiver.

(Prior technology) Currently, MUSE (Multiple
e Sub-nyquist Sample
gt! Experiments have begun on television broadcasting using the ncoding method.

In this MUSE method, a baseband signal containing a luminance signal with a bandwidth of 22 MHz and a chrominance signal with a bandwidth of 7 MHz is frequency modulated, and this is modulated into 1 of the 27 MHz bandwidth of satellite broadcasting.
In order to transmit using the channel, the baseband signal is band-compressed to approximately 8M11z. This band compression is performed by thinning out the complete sampled fish school extracted from the original video signal according to a predetermined rule. When thinning out the sampling points, the resolution in the diagonal direction on the screen is higher than that in the vertical and horizontal directions. Inter-field offset sampling is performed by taking advantage of the viewer's physiological characteristic that the resolution decreases.Also, the viewer's physiological characteristic that in areas of movement, even if the resolution decreases slightly, the viewer does not notice much deterioration in image quality. is also used.

That is, the screen to be transmitted is divided into a moving area and a still area, and the sampling point thinning rate for the moving area is increased compared to that for the still area.

In the decoder on the receiving side, the sampling points thinned out by the encoder on the transmitting side are reproduced based on the sampled fish schools before and after they were actually sent and received, and inserted into the missing points. This process of reproducing and inserting missing sampling points is called interpolation process. This interpolation process includes intra-field interpolation using adjacent sampling fish schools in the same field and inter-field interpolation using sampling fish schools at corresponding positions in adjacent fields. In this interpolation process, a moving area and a still area are detected from the received screen, intra-field interpolation is performed for the moving area, and inter-field interpolation is performed for the still area.

The transmission signal components after inter-field offset sampling on the transmitting side are (vertical resolution 1025 TV lines, horizontal resolution OMHz) and (vertical resolution OTV lines, horizontal resolution 24.3 MHz), as shown by the dashed line in Figure 3. ) is a straight line that slopes downward to the right. As a result of the low-pass filtering processing, sampling frequency conversion processing, and interframe/interline offset sampling processing performed after the interfield offset sampling, the final transmitted signal component is 8.1 MHz from OMHz. M.H.
The band is compressed between 4 Hz and 8.1 MHz, and high frequency components of 8.1 MHz or higher are folded back between 4 Hz and 8.1 MHz.

In the decoder on the receiving side, the signal components indicated by the dashed line in FIG. 3 are decoded by restoring aliasing by frequency conversion, filtering, interpolation, etc., and by reproducing high frequency components. During this decoding, a low frequency permutation method is applied for the purpose of simplifying and economicalizing various processing circuits such as filters. That is, as shown by the solid line in FIG. 3, the processing characteristics in which high vertical resolution components are missing due to insufficient filtering characteristics in the vertical direction are allowed, and the
The high vertical resolution components included in the band below Ml (Z) are cut out and superimposed on the processed signal components. Through this low frequency replacement processing, the high vertical resolution signals accompanying decoding are Compensates for missing ingredients.

The conventional MUSE decoder described above is provided with a still display function that freezes the display screen at a desired time by forming a loop between the input and output of the frame memory necessarily included in the processing circuit. If we try to improve the vertical resolution of this static display screen by the above-mentioned low frequency replacement,
A frame memory is required to store and repeatedly read out the unprocessed signals of the static display screen. However, it is economically difficult to provide an expensive frame memory solely for the special purpose of improving the vertical resolution of a static display screen. For this reason, conventionally, improvement of vertical resolution by low-frequency replacement for static display screens has been omitted.

(Problems to be Solved by the Invention) In the conventional MUSE decoder described above, improvement of image quality by low frequency replacement for a static display screen has been omitted from the viewpoint of economy. However, in a still display screen, deterioration in image quality (blurring) due to the omission of high vertical resolution components is more noticeable than in a normal display screen, so there is a problem in that low frequency replacement is required rather than in the normal case.

(Means for Solving the Problems) The low frequency replacement circuit of the MUSE decoder according to the present invention captures video processing immediately before interframe interpolation processing into a frame memory for motion detection at the start of a still display operation, and repeats this process. It is provided with means for performing low frequency replacement using the low frequency components while reading.

That is, the low-frequency replacement circuit of the present invention replaces the frame memory for motion detection, which is always included in the MUSE decoder and is always unnecessary during the still display operation, with the frame memory that stores the unprocessed signals of the still display screen. By repurposing, it is configured to improve the image quality of static display screens without adding expensive dedicated frame memory.

Hereinafter, the operation of the present invention will be explained in detail together with examples.

(Embodiment) FIG. 1 shows an MU including a low frequency replacement circuit according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating an example of a configuration of a main part of an SE decoder.

In this MUSE decoder, IN is an input terminal for the received video signal, 1 is an A/D conversion circuit, 2 is a preprocessing circuit, 3 is a control signal extraction circuit, 4 is an interframe interpolation unit, 5
is a motion detection section. Further, 6 is a luminance signal processing section, 7 is a chrominance signal processing section, 8 is a low frequency replacement circuit, 9 is a temporary filter, 10 is a line sequential decoder, 11 is a matrix circuit, 12 is an operation command input terminal for static display, 0. ~0. is R
This is an output terminal for lG and B signals.

The MUSE video signal appearing at the input terminal IN is converted into a 10-bit width digital signal by the A/D conversion circuit 1 at a sampling frequency of 16.2 MHz. A preprocessing circuit 2 performs preprocessing such as nonlinear de-emphasis and reverse gamma correction on this A/D converted digital video signal. Control signal extraction circuit 3
extracts a control signal including a motion vector signal, subsample phase information, etc. from the A/D converted digital video signal, and supplies it to the interframe interpolation unit 4, luminance signal processing unit 6, color signal processing unit 7, etc. do.

Although not shown in the figure, this MUSE decoder includes a synchronization extraction circuit that extracts various synchronization signals from the A/D-converted digital video signal, and a synchronization extraction circuit that extracts various synchronization signals from the extracted synchronization signals at 16.2 MHz and 32. 4 MB2゜48.6
Also installed are circuits that reproduce MHz clock signals and supply them to various parts, as well as audio signal separation and decoding circuits.

The video signal output from the preprocessing circuit 2 is processed by an interframe interpolation unit 4 consisting of an interframe interpolation circuit 4a and a frame memory 4b, based on the motion vector signal included in the extracted control signal. Interpolated. The motion detection unit 6, which is composed of a motion detection circuit 6a and a frame memory 6b, determines the magnitude of motion in the screen from the magnitude of the interframe difference signal of one frame or two frames before for the video signal before and after interframe interpolation processing. is detected and supplied to adaptive synthesis units 6C and 70 in the luminance signal processing unit 6 and color signal processing unit 7.

The luminance signal included in the video signal that has been interpolated between frames is
The signal is supplied to an inter-field interpolation circuit 6a through a low-pass filter circuit 6d with a pass band of O to 12 MHz, and subjected to inter-field interpolation processing. Further, the luminance signal included in the video signal that has been interpolated between frames is also supplied to the intra-field interpolation circuit 6b, and subjected to intra-field interpolation processing. The inter-field interpolated graininess signal and the intra-field interpolated luminance signal are adaptively processed in the adaptive synthesis circuit 6C according to a synthesis ratio that is adaptively controlled according to the magnitude of the motion detected by the motion detection circuit 5a. be synthesized. The adaptively synthesized luminance signal undergoes low-pass replacement processing in a low-pass replacer 8a of the low-range replacement circuit 8, and then is supplied to the matrix circuit 11 via a temporary filter 9.

The color signal whose time axis has been expanded by four times in the time axis expansion circuits 7d and 7e is similarly subjected to interpolation processing in the interfield interpolation circuit 7a and the intrafield interpolation circuit 7b. The interpolated color signals are adaptively synthesized in the adaptive synthesis circuit 7C according to a synthesis ratio that is adaptively controlled according to the magnitude of the motion detected by the motion detection circuit 5a. This adaptively combined color signal includes a (R-Y) signal and a (B-Y
) Data compression is applied in which signals appear alternately on every other line. This color signal is converted into a continuous line color signal by line interpolation in the line sequential decoder 10,
The signal is supplied to the matrix circuit 11.

The matrix circuit 11 outputs R and G from the supplied luminance signal Y and color signals (RY) and (B-Y).

B signal is generated and the output terminal 0. ．． 0□, 0. supply to each of them.

Note that in order to avoid complication of illustration, the filters are installed between the low-pass filter circuit 6d and the inter-field interpolation circuit 6a and between the intra-field interpolation circuit 6b and the luminance signal adaptive synthesis circuit 6C in FIG. from 32.4 MHz to 48.6 MHz
The illustration of the frequency conversion circuit is omitted.

If a more detailed explanation is required, please refer to the NE
Please refer to the paper by the present inventors titled "rMUSE Decoder" published in C Technical Report Vol. 1.41 No. 3/1988.

Swift S1 configuring switch 8C of low frequency replacement circuit 8
and 82 are both switched to the upper contacts in the figure during normal operation. Along with this, the video signal that has only been preprocessed in the preprocessing circuit 2 is transferred to the switch 8C and the delay device 8b.
The signal is then supplied to the low frequency replacer 8a.

As shown in FIG. 2, the low-pass replacer 8a has an input terminal 11 that receives the adaptively synthesized luminance signal, an input terminal 8 that receives the preprocessed video signal from the delay device 8b, and a 4 MH.
2-20 MHz bandpass filter 21 and 4 MHz bandpass filter 21
z low-pass filter 22, coefficient unit 23, and adder 2
4 and an output terminal 0. Input terminal 11
The signal component shown by the solid line in Figure 3 that appears in 4
Only the low-frequency components below MH2 pass through the bandpass filter 21 or are supplied to one input terminal of the adder 24 while receiving an appropriate amount of attenuation. On the other hand, the signal component appearing at the input terminal 2, as shown by the one-dot diagonal line in FIG. The signal is multiplied by a coefficient corresponding to the amount of attenuation of the filter 21 and then supplied to the other input terminal of the adder 24 .

The adder 24 synthesizes the filtered signals of the re-input terminals to generate a luminance signal subjected to low frequency substitution at an appropriate ratio as shown by the solid line in FIG. 4, and supplies it to the output terminal O.

When a command signal for static display operation appears at the input terminal 12 in FIG. 1, the operation of the motion detection circuit 5a is stopped, and the switch SL constituting the switch 8C is switched to the lower side in the figure. Along with this, loading of the preprocessed video signal into the frame memory 5b of the motion detection section 5 is started. When this capture is completed, the preprocessed video signal for one frame captured in the frame memory 5b is read out repeatedly at the frame period, and is supplied to the low-frequency replacer 8a via the switch S3 and the delay circuit 8b. .

On the other hand, based on the command signal for static display operation that appears on the input terminal 12, the frame memory 4b of the interframe interpolation unit 4
A loop is formed between the input and output of the frame, and the capture of the video signal of a new frame is prohibited, and the video signal of the frame captured immediately after the command for static display operation is issued is repeatedly read out.

As a result, a still screen is displayed whose vertical resolution has been improved by low frequency replacement.

(Effects of the Invention) As explained in detail above, the low frequency replacement circuit of the present invention has the following features:
Since the frame memory for motion detection, which is always included in the MUSE decoder and is always unnecessary during static display operation, is used as a frame memory that stores unprocessed signals from the static display screen, expensive dedicated The effect is that the image quality of a still display screen can be improved without adding a frame memory.

[Brief explanation of the drawing]

FIG. 1 shows an MUS including a low frequency replacement circuit according to an embodiment of the present invention.
A block diagram showing an example of the configuration of an E decoder, FIG.
3 and 4 are signal component diagrams for explaining the concept of low-frequency replacement. IN...Input terminal for received video signal, 1...A/D conversion circuit, 2...Preprocessing circuit, 4...Interframe interpolation section, 5...Motion detection section, 6...・Luminance signal processing section, 7
...Color signal processing section, 8...Low frequency replacement circuit, 8a...
-Low frequency replacer, 8b...delay device, 8C...switch, 11...matrix circuit. Patent applicant: NEC Home Electronics Co., Ltd. (1 other person)

Claims (1)

[Claims] When the static display operation is not in progress, low frequency components of the video signal immediately before the interframe interpolation process are used for low frequency replacement, and at the start of the static display operation, the video signal immediately before the interframe interpolation process is used as the frame for motion detection. 1. A low-frequency replacement circuit for a MUSE decoder, characterized in that the low-frequency replacement circuit for a MUSE decoder is provided with means for performing low-frequency replacement using the low-frequency components of a memory while repeatedly reading the same.