JPH04314285A - Error correction circuit for digital television signal - Google Patents

Abstract

PURPOSE:To correctly recognize two opposite sample data with an error sample data inbetween and to recognize the direction of optimum correction when the error sample data is generated to recognize a phase of each sample data correctly. CONSTITUTION:An error correction circuit 49 for a digital television signal to correct an error in a MUSE signal recognizes sample data in forward/reverse/ upper right/upper left/lower right/lower left directions adjacent to an error sample data based on a transmission control signal included in the MUSE signal to obtain a difference data between two sample data opposite to each other with the error sample data inbetween in the horizontal/upper right and upper left directions respectively. A direction of a difference data of a minimum value in difference data in each direction is decided to be the correction direction and the error sample data is corrected according to the correction direction.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is directed to MUSE (Multiple Sub-Ny
quistSampling Encoding)
The present invention relates to a digital television signal error correction circuit in a MUSE signal digital recording and reproducing device that records and reproduces signals.

0002

[Prior Art] For example, in a digital VTR that handles digital television signals, when code errors occur due to level fluctuations or omissions in the reproduced signal, noise on the playback screen due to the code errors causes a reduction in image quality. . Therefore, the above-mentioned digital VTR usually corrects sample data with code errors (error sample data) of a digital television signal using an error correction code, and also complements and corrects sample data with adjacent correlated samples. This is designed to prevent code errors from occurring.

That is, first, during recording, redundant data for code error detection and correction is added to a digital television signal and recorded, and during playback, errors in error sample data are corrected based on this redundant data. Correct the error sample data to the original correct data. If the error cannot be corrected using the above error correction code, an error flag is added as a mark to the error sample data that could not be corrected, and the error sample data to which this error flag has been added is This will be supplemented and corrected with samples.

By the way, when performing the above correction, it is important to improve the image quality that the corrected error sample data is similar to the correct sample data when there is no code error in the error sample data. However, in television images, the correlation between adjacent sample data often changes greatly depending on the direction, and if the correction is performed in the wrong direction, the image quality will deteriorate significantly.

[0005] Conventionally, when correcting error sample data, as disclosed in Japanese Patent Application Laid-open No. 58-202683 and Japanese Patent Application Laid-open No. 1-228285,
An error correction method is disclosed that uses sample data adjacent to error sample data to select a good direction for error correction, and uses sample data in this direction to find and replace sample data that approximates the original value of the error sample data. has been done.

To explain the above error correction method in detail, as shown in FIG. From left to right: S-1, S0, S+
1, and for example, the S0th sample data of the nth line is expressed as n·S0. Here, it is assumed that n·S0 is error sample data.

First, in order to determine the optimal direction for correction, the level difference HD in the horizontal direction, the level difference VD in the vertical direction, the level difference RD in the diagonal direction upward to the right, and the level difference LD in the diagonal direction upward to the left are as follows. Find it using the formula.

[0008] HD=|n・S−1−n・S+1|VD=
|(n-1)・S0 −(n+1)・S0 |RD=|
(n-1)・S+1-(n+1)・S-1 | LD=|(
n-1)・S-1-(n+1)・S+1 | HD, VD,
Among RD and LD, the direction with the minimum value is determined to be the most suitable direction for correction, and the error sample data is corrected using sample data in this direction. For example, if VD is the minimum value, the error sample data n・S0 is (n・S0 )'=((n-1)・S0 + (n+1)
・S0)/2 will be corrected.

[0009]

By the way, in order to determine the direction of error correction for error sample data, it is necessary to correctly recognize two sample data facing each other with the error sample data in between.

For example, as shown in FIG.
is error sample data, and when determining the accuracy of correction in the upward-rightward diagonal direction, the level difference in correction in the upward-rightward diagonal direction RD=|(n-1)・S+1−(n+1
)・S−1|, but in this case, the sample position diagonally on the upper right and the sample position diagonally on the lower left for the error sample data n・S0 are mistaken and RD'=
Let |(n-1)·S0 −(n+1)·S-2| be the level difference in the diagonally upward direction.

[0011] Then, RD' becomes inaccurate data representing the accuracy of correction in the diagonally upward direction to the error sample data n.S0. If the value is small and it is mistakenly determined that the upward diagonal direction is the correction direction, the corrected value of the error sample data n・S0 (n・S0
)' will be different from the original value of n·S0.

In the case of a digital television signal obtained by sampling an NTSC television signal or a high-definition television baseband signal at regular intervals, the sampling number in the horizontal scanning line corresponds to the sampling phase of the digital television signal. Correspondingly, it is possible to correctly recognize two sample data in the horizontal direction, vertical direction, upward diagonal direction to the right, and diagonal direction upward to the left, which are opposite to each other with the error sample data in between.

However, in the case of a MUSE signal obtained by band-compressing a high-definition high-definition signal, in order to band-compress the baseband signal, there are
Offset subsampling is performed between frames, and the sampling number and phase of sample data within a horizontal scanning line differ between lines, fields, and frames, so the peripheral area used to determine the correction direction of error sample data Since the sample data does not match the sampling number and changes between lines, fields, and frames, it is not possible to determine the optimal correction direction.

[0014] As described above, in the conventional error correction method,
If the digital television signal is a MUSE signal,
Since the phase of the sample data cannot be accurately grasped, there is a problem in that the direction of the sample data most suitable for modification cannot be detected. Therefore, in the present invention,
It is an object of the present invention to provide an error correction circuit for digital television signals that can solve the above problem by accurately grasping the phase of sample data.

[0015]

[Means for solving the problem] Claims 1 and 2
The digital television signal error correction circuit invented by
In order to solve the above problems, there is provided an error correction circuit for digital television signals that corrects errors in MUSE signals, which has the following features.

That is, the error correction circuit according to claim 1 is based on the MUS
" in the transmission control signal time-division multiplexed with the E signal.
Based on the ``YM subsample phase'' and/or ``C subsample phase'', the sample data adjacent to the error sample data in the front and back, diagonally above the right, diagonally above the left, diagonally below the right, and diagonally below the left are recognized, and the horizontal direction , find the difference data between two sample data facing each other with the error sample data as the center in the diagonal direction upward to the right and the diagonal direction upward to the left, respectively.
The present invention is characterized in that the direction of the minimum difference data among the difference data in these directions is determined as the correction direction, and the error sample data is corrected in accordance with the correction direction.

[0017] Further, the error correction circuit according to claim 2 is provided with an MUS
" in the transmission control signal time-division multiplexed with the E signal.
Based on the inter-field subsample phase "YM", "YM subsample phase", and "C subsample phase," Recognize the sample data, calculate the difference data between two sample data facing each other with the error sample data as the center in the horizontal direction, diagonal direction upward to the right, and diagonal direction upward to the left, and calculate the minimum value of the difference data in each direction. It is characterized in that the direction of the difference data is defined as the correction direction, and the error sample data is corrected in accordance with the correction direction.

[0018]

[Operation] According to the structure of claim 1, in order to recognize sample data based on "YM subsample phase" and/or "C subsample phase", the sample phase of one field of luminance signal and/or chrominance signal can be recognized correctly, and it becomes possible to determine the optimal correction direction for the luminance signal and/or color signal.

According to the structure of claim 2, "interfield subsample phase YM" in the transmission control signal
”, “YM subsample phase”, and “C subsample phase”.
By being able to correctly recognize the sample phase of the field,
It becomes possible to determine the optimal direction for retouching a still image.

That is, according to the configurations of claims 1 and 2 above, it is possible to decode the transmission control signal in the MUSE signal and correctly recognize the phase of each sample data, so that error sample data does not occur. if you did this,
It becomes possible to correctly recognize two sample data facing each other with error sample data in between, and to recognize the optimal direction of correction.

[0021]

【Example】

[Embodiment 1] An embodiment of the invention of claim 1 will be described below with reference to FIGS. 1 to 9.

The digital television signal error correction circuit according to this embodiment corrects the MUSE signal. This is a band compression method developed by NHK. Please note that this content is from NHK
Technical research Showa 62. Volume 39. No. 2. pp18-53
etc. are disclosed.

[0023] The above MUSE method performs offset subsampling and converts the high-definition baseband signal into 8
．． It compresses the band to 1MHz, and is a signal format that can broadcast high-definition television signals in a narrow band.
In addition to TV broadcasting using broadcasting satellites, etc., VTR,
It can be applied to various digital recording and reproducing devices such as video discs.

When a broadcasting satellite is used, as shown in FIG. 4, a MUSE signal in a format having the transmission control signals (hereinafter referred to as control signals) shown in Table 1 by time division multiplexing is transmitted. and this MU
As shown in FIG. 5, the sampling pattern of the SE signal is such that the sample phase is rotated in four fields.

[0025]

[Table 1]

The above-mentioned error correction circuit for correcting the MUSE signal is used in the reproducing system of a digital recording/reproducing apparatus 30 capable of recording and reproducing the MUSE signal, as shown in FIG. This digital recording/reproducing device 30 is an MU
It is connected to a monitor 32 via a MUSE decoder 31 that converts the SE signal b into a baseband signal a, and this digital recording/reproducing device 30 includes a MUSE
The encoder 34 generates a high-definition baseband signal a.
A MUSE signal b converted from the HD baseband signal a (hereinafter referred to as an HD baseband signal a) is input via a broadcasting satellite 33 and a tuner 35.

As shown in FIG. 3, the reproducing system of the digital recording/reproducing apparatus 30 described above has a magnetic head 44 for reproducing signals recorded on a magnetic tape. This magnetic head 44 is connected to a demodulator 46 via an amplifier circuit 45, and the demodulator 46 decodes a signal that has been modulated into a signal suitable for recording during recording.

The above demodulator 46 is connected to an error correction circuit 47, and this error correction circuit 47
The playback data, which is a USE signal, is output to the error correction circuit 49, and the playback signal is corrected by dropout, etc. and errors are detected based on the error correction code added at the time of recording. An error flag is output for data that could not be completed.

The error correction circuit 47 described above is connected to a control signal separation circuit 48 and an error correction circuit 49, and the error correction circuit 49 is connected to the control signal separation circuit 48 and control circuit 50 described above. . The control signal separation circuit 48 extracts only the control signal of the MUSE signal from the data corrected by the error correction circuit 47 and outputs it to the error correction circuit 49. outputs a control signal such as a Y/C switching signal to the error correction circuit 49.

As shown in FIG. 1, the above-mentioned error correction circuit 49 has a control signal decoding circuit 20 to which the above-mentioned control signal is input. This control signal decoding circuit 20 is connected to a sub-sample phase decoding circuit 21.
The Y/C switching signal from the control circuit 50 of FIG. 3 and the MUSE signal from the error correction circuit 47 are input to the circuit.

The above sub-sample phase decoding circuit 21 is as follows:
One input terminal 27 of a switch circuit 27 having a switching terminal 27d into which an error flag from an error correction circuit is input.
a, and is also connected to the multiplexer circuit 22 and absolute value circuits 23, 24, and 25. The absolute value circuit 23 is configured to find the level difference (absolute value) in the horizontal direction between two points of sample data before and after the output data from the sub-sample phase decoding circuit 21, and the absolute value circuit 24 is , the level difference (absolute value) in the diagonal direction upward to the right is determined from two sample data points, diagonally above the right and diagonally below the left of the output data. Further, the absolute value circuit 25 is configured to obtain a level difference (absolute value) in the diagonally upward left direction from two sample data points, diagonally upper left and diagonally lower right of the output data.

The above absolute value circuits 23, 24, and 25 are connected to a multiplexer circuit 22, and the multiplexer circuit 22 is connected to an average value circuit 26. This average value circuit 26 is connected to the other input terminal 27b of the above-mentioned switch circuit 27, and when the error flag is input, the switch circuit 27 outputs the output terminal 27b.
The connection state between C and the input terminals 27a and 27b is switched.

Further, as shown in FIG. 2, the MUS
As shown in FIG. 6, the MUSE decoder 31 to which the E signal is input has an A/D conversion circuit 2 connected to the input terminal 1 to which the MUSE signal is input. is connected to the control signal separation and detection circuit 3 and the de-emphasis circuit 4. The control signal separation detection circuit 3 is connected to a motion detection circuit 5 and a still image processing circuit 6.

On the other hand, the de-emphasis circuit 4 is connected to the above-described motion detection circuit 5 and still image processing circuit 6, and is also connected to a moving image processing circuit 7. , and still image processing circuit 6
is connected to the mixing circuit 8. This mixing circuit 8 is connected to a TCI decoding circuit 9, and the TC
The I decode circuit 9 is connected to an output terminal 11 via a D/A conversion circuit 10.

The operation of the error correction circuit in the above configuration will be explained.

First, as shown in FIG. 2, the HD baseband signal a is converted into the MUSE signal b by the MUSE encoder 34, and transmitted to the digital recording/reproducing device 30 via the broadcasting satellite 33 and tuner 35, where it is recorded. It turns out. When reproducing the digital recording/reproducing device 30, as shown in FIG.
This error correction circuit performs error correction.
The error sample data will be corrected to the original correct data. If the error cannot be corrected by the above-mentioned error correction circuit, an error flag is added as a mark to the error sample data that could not be corrected, and as shown in FIG.
It will be output to.

On the other hand, the error-corrected MUSE signal from the error correction circuit 47 is sent to the sub-sample phase decoding circuit 21.
, the subsample phase decoding circuit 21 outputs the output data to the input terminal 27a of the switch circuit 27. At this time, the subsample phase decoding circuit 21
, the "b9 YM subsample phase" and "b10 C subsample phase" of the control signal from the control signal decoding circuit 20 are input, as well as the Y/C switching signal from the control circuit. There is.

The subsample phase decoding circuit 21 described above determines the "b9 YM subsample phase" and "b1
0 C subsample phase", the subsample phase of the output data to be output to the switch circuit 27 is determined, and the subsample phase of the output data to be outputted to the switch circuit 27 is determined, and the subsample phase of the output data is determined based on the sample data of the front and rear, diagonally upper right, and diagonally left within the same horizontal scanning line as neighboring sample data of the output data. Above, diagonally below right,
The sample data on the diagonally lower left side is output to the multiplexer circuit 22.

Furthermore, the above sample data before and after are also output to the absolute value circuit 23, and this absolute value circuit 23 calculates the horizontal level difference (absolute value) between the two sample data before and after. It will be done. In addition, the sample data at the upper right and lower left are the absolute value circuit 2.
4, and the absolute value circuit 24 determines the level difference (absolute value) in the diagonally upward right direction between the two sample data points, diagonally upper right and diagonally lower left. Furthermore, the sample data at the upper left and the lower right are also output to the absolute value circuit 25, and the absolute value circuit 25 determines the level difference in the upper left diagonal direction between the two sample data at the upper left and the lower right. absolute value) is required.

As a result, the multiplexer circuit 22 receives sample data before and after the output data from the sub-sample phase decoding circuit 21, diagonally upper right, diagonally upper left, diagonally lower right,
Sample data diagonally lower left, absolute value circuits 23, 24, 2
Level differences from 5 in the horizontal direction, upward diagonal direction to the right, and diagonal upward direction to the left are input.

Then, the multiplexer circuit 22 compares the level difference between the horizontal direction, the diagonal direction upward to the right, and the diagonal direction upward to the left, and outputs two points of sample data in the direction having the minimum level difference. That is, for example, if the output of the absolute value circuit 23 for determining the level difference in the horizontal direction is the minimum, the multiplexer circuit 22 will output sample data before and after the output data. Then, the two sample data from the multiplexer circuit 22 are input to the average value circuit 26, and the average value circuit 26 is
The average value of these sample data is outputted to the other input terminal 27b of the switch circuit 27 as modified data.

The error flag from the error correction circuit described above, the output data from the subsample phase decoding circuit 21, and the modified data from the average value circuit 26 are input to the switch circuit 27, and the switch circuit 27 27 uses the error flag signal as an output data switching signal, and if there is no error flag signal, outputs the output data as is,
If the error flag is set, corrected data will be output. As a result, a direction suitable for error correction is selected for the MUSE signal b using sample data adjacent to the error sample data, and the sample data in this direction is used to convert the MUSE signal b into sample data that approximates the original value of the error sample data. It will be corrected.

[0043] When the MUSE signal b is corrected by the above error correction circuit and outputted from the digital recording/reproducing device 30,
The MUSE signal b is input to the MUSE decoder 31, as shown in FIG. The operation of this MUSE decoder 31 will be explained below.

In this MUSE decoder 31, as shown in FIG. 6, the MUSE signal input through the input terminal 1 is converted into a digital signal by the A/D conversion circuit 2, and the MUSE signal is converted to a digital signal by the control signal separation detection circuit 3 and the de-emphasis signal. This will be input to circuit 4.

The control signal separation detection circuit 3 is shown in Table 1.
The control signal in the MUSE signal is detected, and the data processing method of the still image processing circuit 6 and the content of the output signal of the motion detection circuit 5 are controlled depending on the content of the control signal.

On the other hand, the de-emphasis circuit 4
After the signal from the conversion circuit 2 is subjected to processing inverse to the emphasis processing applied for transmission, it is output to the motion detection circuit 5, the moving image processing circuit 7, and the still image processing circuit 6. Then, the motion detection circuit 5 detects a moving area of the image and forms a motion signal by taking the difference between the 1st (first) frame and the 2nd (second) frame of the input MUSE signal, and the mixing circuit The moving image processing circuit 7 performs only intra-field interpolation to form a moving image signal, and outputs it to the mixing circuit 8.

Further, the still image processing circuit 6 performs interframe interpolation using four field signals, and then performs interfield interpolation to generate a still image signal using all four types of sample points. It will be formed and output to the mixing circuit 8.

The mixing circuit 8 mixes or switches the moving image signal and the still image signal for each pixel according to the above-mentioned motion signal, and outputs the mixture to the TCI decoding circuit 9. and,
When the output signal of the mixing circuit 8 is input to the TCI decoding circuit 9, the line-sequential/time-division multiplexed luminance signal and color difference signal are TCI-decoded and the D/A conversion circuit 9 receives the output signal from the mixing circuit 8.
0, it is converted into an analog signal by the D/A conversion circuit 10, and is output from the output terminal 11 to the monitor 32 in FIG.

In the still image processing, interpolation processing is performed using all the sample points of four fields to form a still image signal, so it is necessary to know the sample phase of the sample points for the interpolation processing. The data showing this sample phase is
Since it is written in the control signal shown in Table 1, its contents are detected by the control signal separation and detection circuit 3, and the phase with respect to the previous frame and field is determined to obtain a good image.

Next, the case where the luminance signal is corrected within the field by the error correction circuit of this embodiment will be explained.

FIG. 7 shows that among the luminance signals of one field,
It represents three consecutive horizontal scanning lines n-1, n, and n+1. S at each horizontal scan line
K-1 to SK+2 represent sampling numbers within the horizontal scanning line; for example, the SK-th sample data of the n-th line is represented as n·SK. Here, assuming that n・SK is the error sample data,
In order to modify n・SK, consider sample data around n・SK.

In the case shown in FIG. 7, the sample data before and after the same horizontal scanning line as n·SK are n·SK−1,
n・SK+1, the sample data diagonally on the upper right of n・SK is (n-1)・SK+1, the sample data diagonally on the upper left is (n−1)・SK, and the sample data diagonally on the lower right is (n+1)・SK+1 , the sample data diagonally at the lower left is (n+1)·SK.

However, in the MUSE signal, between lines and
Since offset subsampling is performed between fields and frames, the sample phase differs depending on the field even if the line number and sampling number are the same. FIG. 8 shows a diagram of a field when the line numbers and sampling numbers are the same as those in FIG. 7 but the sample phases are different.

In FIG. 8, the error sample data is n
・SK, then the sample data before and after the same horizontal scanning line as n・SK are n・SK−1, n・
SK+1, which is the same as in the case of FIG. However, the sample data diagonally to the upper right of n・SK is (n-1)
・SK, the sample data on the diagonal upper left is (n-1)・S
K-1, the sample data on the diagonal lower right is (n+1)・S
K, the sample data at the lower left diagonally is (n+1)・SK-
1, which is different from the case in FIG.

In this way, even if the MUSE signal has the same line number and sampling number, it has two sampling phases as shown in FIGS. 7 and 8. In the case of a luminance signal, the sample phase within the field can be determined by decoding "b9YM subsample phase 1 when the sample point is on the right on an odd line" of the control signal in Table 1, and as shown in FIG. It can be determined whether it is the sample phase or the sample phase of FIG.

That is, in order to determine the optimal correction direction for correcting the error sample data n・SK, the level difference HD in the horizontal direction between two points facing each other with the error sample data n・SK in between, and the diagonal direction upward to the right. level difference RD
, find the level difference LD in the diagonal upward left direction. As a result, the sample phases HD, RD, and LD in FIG.
It will look like this:

[0057] HD=|n・SK−1 −n・SK+1
|RD=|(n-1)・SK+1 −(n+1)・SK
|LD=|(n-1)・SK −(n+1)・SK+
1 | Also, the sample phases HD, RD, and LD in FIG. 8 are as follows.

[0058] HD=|n・SK−1 −n・SK+1
|RD=|(n-1)・SK −(n+1)・SK-1
|LD=|(n-1)・SK-1 −(n+1)・S
K | Next, the level difference HD in the horizontal direction, the level difference RD in the diagonal upward-right direction, and the level difference LD in the diagonal upward-left direction
Among them, the direction with the minimum value is determined to be the direction suitable for modification, and the modification value for modifying the error sample data n.SK is set as (n.SK)'. In the case of the sample phase in FIG. 7, if the horizontal level difference HD is the minimum value, then (n・SK)'=(n・SK−1 +n・SK+1
)/2.

Furthermore, if the level difference RD in the upward and diagonal direction is the minimum value, then (n·SK)'=((n-1)·SK+1 +(
n+1)・SK )/2, and if the level difference LD in the upward left diagonal direction is the minimum value, (n・SK )'=((n-1)・SK + (n+
It will be modified by 1)・SK+1)/2.

On the other hand, in the case of the sample phase shown in FIG. 8, if the horizontal level difference HD is the minimum value, then (n·SK
)'=(n・SK-1 +n・SK+1)/2, and if the level difference RD in the upward and diagonal direction is the minimum value, then (n・SK)'=((n-1)・SK +(n+
1)・SK-1)/2, and if the level difference LD in the upward left diagonal direction is the minimum value, (n・SK)'=((n-1)・SK-1 +(
It will be corrected by n+1)・SK)/2.

[0061] As a result, the error correction circuit of this embodiment is as follows.
Even for signals such as MUSE signals that undergo line-to-line, inter-field, and inter-frame offset subsampling, it is possible to determine the optimal correction direction by accurately recognizing the sample phase of the luminance signal. , it is now possible to perform good corrections.

Next, a case will be described in which a color signal is corrected within a field using the error correction circuit of this embodiment.

Color signal (R-YM) in MUSE signal
, B-YM), inter-frame offset subsampling is performed with an offset of two lines, and two types of color signals are time-division multiplexed for each line. and,
Similar to the luminance signal in Example 1, this color signal undergoes offset subsampling between lines, fields, and frames, so as shown in FIGS. 9 and 10, the same line number and the same sampling There are two types of sample phases even for numbers. However, FIGS. 9 and 10 are diagrams showing only one color signal.

First, if n·SK of the color signal having the sample phase shown in FIG. 9 is error sample data, then
The sample data before and after in the horizontal scanning line for correcting n・SK are n・SK−1, n・SK+1, and the sample data diagonally on the upper right is (n−2)・SK+
1. The sample data diagonally on the left is (n-2)・SK
, the sample data diagonally below the right is (n+2)・SK+1
, the sample data diagonally below the left is (n+2)·SK.

Next, if n·SK of the color signal having the sample phase shown in FIG. 10 is error sample data, the sample data before and after the horizontal scanning line for correcting n·SK is -1, n・SK+1
The sample data diagonally on the upper right is (n-2)・SK
, the sample data diagonally on the left is (n-2)・SK-1
, the sample data diagonally below the right is (n+2)・SK,
The sample data on the lower left side is (n+2)·SK-1.

The sample phase of the above color signal can be determined by decoding the control signal in the same way as the luminance signal, b10 "C subsample phase line number/2
When is an odd number and the sample point is on the right, the sample phase can be determined from 1'' (see Table 1).

As a result, the color signals are as shown in FIGS. 9 and 10.
Regardless of the sample phase, the control signal allows sample data before and after the same horizontal scanning line as n・SK, sample data diagonally above the right, diagonally above the left, diagonally below the right, and diagonally below the left of n・SK. Accurately recognizes n・SK
The level difference HD in the horizontal direction, the level difference RD in the diagonal direction upward to the right, and the level difference LD in the diagonal direction upward to the left are found between two points facing each other with the two points in between, and correction can be performed in the direction having the minimum value.

In this way, the error correction circuit of this embodiment is
“b9 YM subsample phase” and “b10
"C subsample phase" is read, and the sample data adjacent to the error sample data in the front and back, diagonally upper right, diagonally upper left, diagonally lower right, and diagonally lower left are recognized, and then the horizontal direction, diagonally upward right direction, After obtaining the difference data of two sample data facing each other with the error sample data as the center in an upward left diagonal direction, and determining that the direction of the minimum difference data among the difference data in each direction is the correction direction,
It is set to be fixed.

[0069] As a result, the error correction circuit of this embodiment is as follows.
By accurately recognizing two sample data points in the horizontal direction, upward diagonal direction to the right, and diagonal direction upward to the left that are opposite to each other across the error sample data to be corrected, the luminance signal and color signal can be corrected in the optimal direction. It is possible to correct it.

[0070] The above sample phase may be recorded as is during recording and determined by decoding the control signal during playback, or it may be determined by decoding the control signal during recording and then determining the decoded control signal during playback. It may be determined based on the signal.

In addition, in this embodiment, "b9 YM subsample phase" and "b1
0 C subsample phase" to correct both the luminance signal and the color signal, but the invention is not limited to this; "b9 YM subsample phase" or "b10 C subsample phase"'' may be used to modify only either the luminance signal or the color signal.

[Embodiment 2] Another embodiment of the invention of claim 2 will be described as follows. Note that the circuit configuration of the error correction circuit is the same as that of the first embodiment described above, so its explanation will be omitted.

First, "b1 inter-field sub-sample phase YM", "b9 YM sub-sample phase" and "
b10 "C subsample phase" is read, and the front and back adjacent to the error sample data, diagonally upper right, diagonally upper left,
Sample data diagonally lower right and diagonally lower left will be recognized.

After that, difference data between two sample data facing each other with the error sample data as the center is obtained in the horizontal direction, diagonally upward to the right direction, and diagonally upward to the left direction, and the minimum of the difference data in each direction is calculated. After the direction of the value difference data is determined as the correction direction, it will be corrected.

[0075] As a result, the error correction circuit of this embodiment is as follows.
By accurately recognizing two sample data points in the horizontal direction, upward diagonal direction to the right, and diagonal direction upward to the left that face each other across the error sample data to be corrected, correction can be performed in the optimal correction direction. It has become. In the case of this error correction circuit, it is possible to perform correction using four fields of sample data, so in particular,
The still image of the MUSE signal uses 4 fields of data to form one screen, and the correlation between each field is high, making it possible to retouch still images well. There is.

[0076]

Effects of the Invention As described above, the digital television signal error correction circuit of the invention of claim 1 corrects errors in the MUSE signal. Based on the "YM subsample phase" and/or "C subsample phase" in the middle, the sample data adjacent to the error sample data before and after, diagonally upper right, diagonally upper left, diagonally lower right, and diagonally lower left are recognized. , find the difference data of two sample data facing each other with the error sample data as the center in the horizontal direction, diagonal direction upward to the right, and diagonal direction upward to the left, and calculate the direction of the difference data of the minimum value among the difference data in each direction. The error sample data is corrected according to the correction direction.

[0077] As a result, "YM subsample phase"
Since the sample data is recognized based on the "C subsample phase" and/or "C subsample phase", the sample phase of one field of luminance signal and/or chrominance signal can be correctly recognized, and the luminance signal and/or chrominance signal can be optimally modified. This has the effect of making it possible to determine the direction.

Further, in the digital television signal error correction circuit of the invention of claim 2, as described above, the digital television signal error correction circuit for correcting errors in the MUSE signal is time-division multiplexed on the MUSE signal. "Interfield subsample phase YM" in the transmission control signal
”, “YM subsample phase”, and “C subsample phase”, the sample data adjacent to the error sample data before and after, diagonally upper right, diagonally upper left, diagonally lower right, and diagonally lower left are recognized, Find the difference data between two sample data facing each other with the error sample data as the center in the horizontal direction, diagonal direction upward to the right, and diagonal direction upward to the left.
The direction of the difference data having the minimum value among the difference data in each direction is determined as the correction direction, and the error sample data is corrected in accordance with the correction direction.

[0079] As a result, "
Since the sample data is recognized based on the inter-field subsample phase YM, YM subsample phase, and C subsample phase, it is possible to correctly recognize the sample phase of 4 fields, allowing for the optimal correction direction for still images. This has the effect of making it possible to determine.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an error correction circuit of the present invention.

FIG. 2 is an explanatory diagram showing an example of use of a digital recording/reproducing device.

FIG. 3 is a block diagram showing a playback system of the digital recording and playback device.

FIG. 4 is an explanatory diagram showing the format of a MUSE signal.

FIG. 5 is an explanatory diagram showing a sample phase of a MUSE signal.

FIG. 6 is a block diagram of a MUSE decoder.

FIG. 7 is an explanatory diagram showing the sample phase of the MUSE signal.

FIG. 8 is an explanatory diagram showing the sample phase of the MUSE signal.

FIG. 9 is an explanatory diagram showing the sample phase of the MUSE signal.

FIG. 10 is an explanatory diagram showing the sample phase of the MUSE signal.

FIG. 11 shows a conventional example and is an explanatory diagram showing sample phases.

[Explanation of symbols]

20 Control signal decoding circuit 21
Subsample phase decoding circuit 22 Multiplexer circuit 23 Absolute value circuit 24 Absolute value circuit 25 Absolute value circuit 26 Average value circuit 27 Switch circuit 30 Digital recording/reproducing device 31 MUSE decoder 32 Monitor 33 Broadcasting satellite 34 MUSE encoder 35 Tuner 44 Magnetic head 45 Amplifier Circuit 46 Demodulator 47 Error correction circuit 48 Control signal separation circuit 49 Error correction circuit 50 Control circuit

Claims (2)

[Claims] Claim 1: A digital television signal error correction circuit for correcting errors in a MUSE signal, the circuit comprising:
Based on the "YM subsample phase" and/or "C subsample phase" in the transmission control signal that the signal has, the front and back, diagonally upper right, diagonally upper left, diagonally lower right, and diagonally lower left adjacent to the error sample data are Recognize the sample data of An error correction circuit for a digital television signal, characterized in that the direction of the difference data is defined as a correction direction, and error sample data is corrected in accordance with the correction direction. 2. A digital television signal error correction circuit for correcting errors in a MUSE signal, wherein the MUSE signal
Based on the "interfield subsample phase YM", "YM subsample phase", and "C subsample phase" in the transmission control signal that the signal has, , recognize the sample data diagonally downward to the right and diagonally downward to the left, horizontally,
Obtain the difference data between two sample data facing each other with the error sample data as the center in the upward diagonal direction to the right and the diagonal upward direction to the left, and determine the direction of the minimum difference data among the difference data in each direction as the correction direction. , an error correction circuit for a digital television signal, characterized in that it corrects error sample data according to a correction direction.