JPH0241085A - Muse decoder - Google Patents

Abstract

PURPOSE:To prevent deterioration in the picture quality by supplying a subsample phase bit over four field periods during holding under a prescribed condition to a video processing section in the order of holding cyclicly. CONSTITUTION:An output of an OR gate 16 goes to a low level in the case of not being in the still picture display mode when the synchronizing system and the detection of subsample phase bit are normal and each subsample phase bit outputted from a control signal separator circuit 6 is fed to a video processing section 5 through a switch 14 without any modification. If out of synchronism takes place, or the detection of the subsample phase bit is not normal or the still picture display mode is selected, the output of the OR gate 16 goes to a high level. Then the bit is outputted from the control signal separation circuit 6 and subject to delay over 4 fields by holding circuits 11, 12, 13 and the resulting subsample phase bit is fed sequentially to the video processing section 5 sequentially via the switch 14.

Description

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

(Prior technology) Currently, MUSE (Multiple
e Sub-nyquist Sampling f
Experiments have begun on television broadcasting using the incoding 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.
For transmission using a channel, the baseband signal is band-compressed to approximately 8 MHz. 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 sampling points, inter-field offset sampling is performed using the physiological characteristic of the viewer that the resolution in the diagonal direction on the screen is lower than in the vertical and horizontal directions. In addition, the physiological characteristic of viewers is used that they do not get upset about the deterioration of image quality much even if the resolution decreases to some extent in moving areas.

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. The process of playing back and inserting this missing sampling point is as follows:
This is called interpolation processing.

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. For 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.

Also, when interpolating between fields for a static region,
The phase of the transmitted sample points is shifted little by little for each field at a period of 4 fields, and on the receiving side, reproduction is performed by combining the sample points of 4 fields, thereby improving the resolution. The combination of sample points for four fields on the receiving side is performed based on subsample phase bits included in the control signal in the MUSE signal sent in field units. Note that in the MUSE method, sub-Nyquist sampling is performed at a frequency less than twice the highest frequency fm of the input signal, so the term subsampling is also used instead of sampling.

(Problems to be Solved by the Invention) The MUSE decoder currently under development is capable of handling cases where the synchronization system fails to detect the synchronization signal, or when sub-sample phase bits are not detected correctly. However, there is a problem in that sample points for four fields are not properly combined, resulting in deterioration of image quality.

Also, hold the video signal over 4 fields,
Deterioration of image quality also becomes a problem in the still image mode in which still images are displayed by cyclically repeating these processes. Instead of the subsample phase bits added to the video signal for 4 fields to be displayed as a still image, subsample phase bits with a period of 4 fields received after the start of displaying the still image are used to display the still image. This is because the image is assembled. That is, if the subsample phase bits change due to movement in the screen, subsample points will be assembled based on a phase different from the actual one.

(Means for Solving the Problems) The MUSE decoder of the present invention includes a holding section that holds a subsample phase bit detected as a part of a control signal for a period of four fields, and a holding section that holds a subsample phase bit detected as a part of a control signal, and a subsample phase bit that is detected as a part of a control signal. If the phase bit is not detected normally, or if a still image is displayed by sequentially outputting the video signal of the four fields being held, the phase bit is detected as part of the above control signal. supply control means for cyclically supplying sub-sample phase bits over a period of four fields being held to the holding section and to the video processing section in place of the sub-sample phase bits of .

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

(Embodiment) FIG. 1 is a configuration block diagram of a MUSE decoder according to an embodiment of the present invention.

In this MUSE decoder, TN is an input terminal for the MUSE signal, 1 is a BS (MUSE) tuner, 2 is a low-pass filter, 3 is an A/D conversion circuit, 4 is a synchronization detection circuit, 5 is a video processing section, and 6 is a control signal Minute H circuit, 7
1 is a clock generation circuit, 8 is an audio decoder, and 10 is a subsample phase bit holding/supplying section.

The input terminal IN is connected to the 12GH signal received by the BS antenna.
A MUSE signal which is an RF multiplied signal of z and converted to an intermediate frequency of 1.3 GHz is supplied. This MUSE signal is
The signal is converted into a baseband signal by the BS tuner 1, supplied to the A/D conversion circuit 3 through the low-pass filter 2, and converted into a digital signal. This digital MUSE signal is supplied to a synchronization detection circuit 4, a video processing section 5, and a control signal separation circuit 6. The clock generation circuit 7 is
Generates various clock signals based on synchronization signals such as frame pulses and HD signals detected by the synchronization detection circuit 4,
The signal is supplied to the video processing unit 5, audio decoder 8, and the like. A/D
The digital audio signal output from the conversion circuit 3 is decoded by an audio decoder 8 and supplied to a subsequent audio output section (not shown).

The subsample phase bit holding/supplying section 10 is composed of holding circuits 11, 12, 13, switches 14, 17, and two-manual OR gates 15, 16.

The holding circuit 11 maintains the Y subsample phase bit by cascading four stages of launch circuits (Z-') that give a delay time of one field to the Y subsample phase bit output from the control signal separation circuit 6. 4
Retain for the duration of the field. Similarly, the holding circuits 12 and 13 are latch circuits (Z-' ) are connected in series over four stages to maintain the Y subsample phase bit and the interfield subsample phase focus over the period of four fields.

When an out-of-synchronization occurs in the built-in PLL in the clock generation circuit 7, the voltage of the signal line connected to one input terminal of the two-man OR gate 15 is raised from low to high. In addition, if the sub-sample phase bit is not detected normally in the control signal separation circuit 6 due to an uncorrectable code error, etc., the voltage of the signal line connected to the other input terminal of the two-man OR gate 15 changes from low to high. will be launched. The output terminal of this two-man powered OR gate 15 is connected to one input terminal of a two-man powered OR gate 16.

Further, when the viewer of this MUSE decoder closes the switch 17 to enter the still image display mode, the voltage of the signal line connected to the other input terminal of the two-man OR gate 26 is raised from low to high.

Switch 14 controlled by the output of two-man power OR gate 16
The contact point is switched to the upper side in the figure if the output of the two-man power OR gate 1-16 is low, and is switched to the lower side in the figure if the output of the two-man power OR gate 16 is high.

Therefore, if the synchronization system is normal, subsample phase bit detection is normal, and the still image display mode is not in effect, the output of the OR gate 16 will be low, and each subsample phase bit output from the control signal separation circuit 6 will be The signal passes through the switch 14 as it is and is supplied to the video processing section 5.

On the other hand, if synchronization occurs, if the detection of the subsample phase bit is not normal, or if the still image display mode is selected, the output of the OR gate 16 becomes high, and the output is output from the control signal separation circuit 6. Then, the sub-sampled phase bits delayed for four fields in each of the holding circuits 11, 12 and OR gates 13 are sequentially and cyclically supplied to the video processing unit 5 via the switch 14.

Note that among the control signals separated and detected by the control signal separation circuit 6, those other than the sub-sample phase bits, such as motion vectors, are directly supplied to the video processing section 5.

The video processing section 5 includes a preprocessing section that performs preprocessing such as nonlinear de-emphasis and reverse gamma correction, an interframe interpolation section, a motion detection section, a luminance signal processing section, and a color signal processing section. The luminance signal and color signal are interpolated using inter-field interpolation for static areas, and intra-field interpolation for moving areas, and the processing results of both systems are processed according to the motion detection results. The signals are combined with weighting, converted into analog R, G, and B signals, and output. For more detailed configuration of this video processing section 5, please refer to N.
Please refer to the paper by the present inventors entitled "rMUSE Decoder" published in EC Technical Journal Vol. 1.41 No. 3/1988.

(Effects of the Invention) As described above in detail, the MUSE decoder of the present invention retains the sub-sample phase bits detected as part of the control signal over a period of four fields, and under predetermined conditions. Since the sub-sample phase bits over the period of four fields that are being held are supplied to the video processing unit cyclically in the order in which they are held, synchronization may occur, sub-sample phase bit detection may fail, or there may be times when the sub-sample phase bits are stopped. Even when the image display mode is started, it is possible to effectively prevent image quality from deteriorating due to inappropriate combinations of sub-sample points.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the configuration of a MUSE decoder according to an embodiment of the present invention. l...BS tuner, 3...A/D conversion circuit, 5.
...Video processing unit, 6...Control signal separation circuit,
7... Clock generation circuit, 10... Sub sample phase bit holding/supplying section, 11.12.13... Sub sample phase bit holding section, 14.17... Switch. Patent applicant: NEC Home Electronics Co., Ltd. ()1.1)7))

Claims (1)

[Claims] In a decoder for a MUSE signal in which the phase difference between subsample points between adjacent fields is changed at a period of four fields, the subsample phase bits detected as part of the control signal are changed over a period of four fields. When the holding unit and the synchronization system are not normal, when the detection of the sub-sample phase bits is not performed normally, or when displaying a still image by sequentially and repeatedly outputting the video signal for the four fields being held. supply control means for cyclically supplying the sub-sample phase bits over the period of the four fields being held to the video processing unit in place of the sub-sample phase bits just detected as part of the control signal; A MUSE characterized by having
E-decoder.