JPS6253090A - Digital television receiver - Google Patents

Abstract

PURPOSE:To obtain a high quality picture and to easily cope with a freezing and component signal by separating the signal into a signal in a band in which a brightness signal exists and one in a band where a color signal is included, and eliminating unnecessary signals included in respective one of the said separated signals. CONSTITUTION:A composite signal inputted from an input terminal 1 is quantized by an A/D converter 4 and is converted to a digital signal, from which an unnecessary component that is the color signal is removed by a first frequency selection circuit 5, and then outputted as a brightness signal from a first output terminal. Meanwhile, the band that includes a color signal (for instance the band higher than 2MHz in NTSC) is selected by a second frequency selection circuit 6, and thereafter a third frequency selection circuit 7 removes unnecessary brightness signal existing in the said band, and the signal is outputted as a color signal from a second output terminal 3.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a digital television receiver, and in particular, to a digital television receiver with high image quality and
The present invention relates to a digital T7V receiver suitable for realizing multiple functions.

[Background of the invention]

Digital technology, especially semiconductor technology, has made remarkable progress, and so-called digital television receivers have appeared in which the signal processing system of television receivers is also digitalized. This digital TV receiver uses a comb-shaped frame for easy introduction of memory for a more complete shine! Attention has been focused on separating signals and color signals.

For example, as described in Japanese Patent Application Laid-Open No. 58-115995, color signals are separated using a frame comb shape for still images and a line comb shape for moving images, and this color signal is separated from the original signal. The subtraction is performed to separate the luminance signal, so that a high-resolution image without cross colors or dots can be obtained in the still image portion.

However, frame memory is not only used to separate luminance signals and chrominance signals, but can also be used to freeze input images, but conventional devices were not designed for this purpose. .

Conventional devices freeze the composite signal as it is, but as is well known, for example, in NT8C, the phase of the color subcarrier is reversed between frames, and when freezing one frame, the phase is reversed between frames. It becomes difficult to extract normal color subcarriers. This drawback can be avoided by freezing only one or two frames, but since the image is played over four fields, in the case of a moving image, the movements of the four fields are repeatedly played back, making it unsightly.

Furthermore, it becomes difficult to perform noise removal using interframe correlation.

Furthermore, in current television receivers, the signals inputted are not only the front/back signal, but also the R, GB, and other congonent signals. Even when freezing such a congonent signal, it is difficult to use this frame memory in conventional devices.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a digital television receiver that can not only provide high image quality but also have multiple functions such as support for inputting 7-Leads and Humbond signals.

[Summary of the invention]

That is, in the first aspect of the present invention, after AD converting the input signal, first, it is broadly divided into a signal of the entire band (that is, a band in which the luminance signal exists) and a signal in the band including the color signal. . Remove unnecessary components contained in each signal from these two signals (in other words, remove the color signal component from the entire band signal, and remove the luminance signal component from the signal in the band that contains the color signal, respectively) ) is provided with a frequency selection circuit that focuses on this.

The invention of 11!2 provides a means for easily stopping the frequency selection operation, and includes providing a switch at the output of a frequency selection circuit for extracting unnecessary components, and mixing the output of this switch with the original signal. Accordingly, the frequency selection operation for removing unnecessary components is activated or stopped.

[Embodiments of the invention]

An embodiment of the present invention is shown in FIG. 1. In FIG. 1, 1
is the input terminal of @1, 2 is the first output terminal, 3 is the second output terminal, 4 is the AD converter, 5 is the first frequency selection circuit,
6 is a second frequency selection circuit, and 7 is a third frequency selection circuit.

The composite signal input from the first input terminal 1 is A
The signal is quantized by a D converter 4 and converted into a digital signal. Thereafter, the color signal, which is an unnecessary component, is removed by the first frequency selection circuit 5, and the signal is output from the first output terminal as a luminance signal. On the other hand, the second frequency selection circuit 6 selects the band in which the color signal is included (for example, in NT8C, a frequency band higher than 2M1lz), and the third frequency selection circuit 7 further selects unnecessary luminance within this band. The signal is removed and output as a color signal from the second output terminal 3.

This third frequency selection circuit 7 only needs to be able to remove unnecessary luminance components within the color signal band, and there is no need to extract the luminance signal component at the correct frequency, so it can also be implemented in the embodiment shown in FIG. .

In FIG. 112, 8 is a color difference signal demodulation circuit, and 9 is a fourth frequency selection circuit. The color difference signal demodulation circuit 8 generates a color difference signal, for example (R-Y, B
-Y), and the two demodulated color difference signals are used separately or together in a time-axis multiplexed state, and then the two demodulated color difference signals are combined into a second color difference signal having a comb-shaped filter that removes unnecessary luminance signals. The signal is inputted to the frequency selection circuit 9 of No. 4, and a color difference signal from which unnecessary luminance signals are removed is obtained.

The first frequency selection circuit 5 shown in FIG. 1 may have a configuration as shown in FIG. 3, for example. In FIG. 3, 10 is a tll input terminal, 11 is a third output terminal, 12 is a frame comb, 13 is a line comb, and 14 is a first mixing circuit. The AD-converted combo shift signal is the second
It is input from the input terminal 10 of. The frame comb 12 has a frame memory capable of storing at least one frame's worth of signals, and adds signals of different times for one frame. As is well known, in NTSC, in the case of a still image, the polarity of the color signal is reversed between frames, so when signals that differ in one frame time are added, the color signal is completely removed. In the line comb 13, for example, signals having different times during one horizontal scanning period are added. If this is done, as is well known, the color subcarrier frequency is selected so that its polarity is reversed after one horizontal scanning period, so in a picture with strong vertical correlation, color signals are largely removed by this process. In the mixing circuit, when it is a still image, the output of frame comb 12 is
When it is a moving image, the output of the line comb 13 is output, so that the ID of the image is output! The mixed device is controlled according to the movement of each element. This movement can be determined, for example, by using a frame memory used in the frame comb 12 and detecting a level difference between one frame.

This frame comb shape can be realized, for example, by the method shown in Fig. 4. In Fig. 4, 15 is a third input terminal, 16 is a fourth output terminal, 17 is a polarity inversion circuit, and 18 is a frame memory. ,
19 is a first addition circuit, 20 is a high frequency pass filter, 2
1 is a second addition circuit. The combo shift signal input from the third input terminal is sent to the polarity inverting circuit 17. Frame memory 18. The frames are processed by a frame comb circuit consisting of a first adder circuit 19, and inter-frame differences are determined. Furthermore, a high frequency pass filter 20 extracts the frequency band containing the color signal. In this way, in the case of a still image, the brightness signal has exactly the same level and the same polarity between frames, and the color signal has reverse polarity, so only the color signal is separated in the output of the high frequency pass filter 20. be done. , Well, at this time, the color signal and level of the combo shift signal that is also input to the third input terminal 15 are exactly the same, and only the polarity is reversed.
By performing the addition in the second addition circuit 21, a luminance signal from which the color signal has been completely removed is obtained at the fourth output terminal 16. By using the frame memory in this way, it is possible to realize a frame comb 12 that almost completely removes unnecessary color signals.

Using this idea, the first frequency selection circuit 5 can also be realized in the form shown in FIG.

That is, 22 is a second frame comb, 23 is a second line comb, and 24 is a third adder circuit.

The second frame comb 22 is, for example, a frame comb circuit for extracting unnecessary color signals, which is composed of a polarity inversion circuit 17, a frame memory 18, and a first addition circuit shown in FIG. 4, and a second line. The comb 23 extracts unnecessary color signals by subtracting signals separated by, for example, one horizontal scanning period. ■・
A mixing circuit 14 that controls the mixing ratio according to the movement of the image outputs the output of the second frame comb 22 when the image is a still image, and outputs the output from the second line comb 23 when the image is a moving image. A first frequency selection circuit that removes unnecessary color signals in an optimal form according to the movement by outputting the output of , at an intermediate mixing ratio according to the amount of movement, and adding it to the original signal. 5 can be achieved.

Furthermore, when the original signal is not frequency multiplexed and a component signal such as only a luminance signal is input, this frequency selection operation is not necessary. This can be easily implemented by simply providing a switch circuit 25 as shown in FIG. 6, for example, to stop the addition operation.

Furthermore, considering the comb operation, whether it is a frame comb or a line comb, the original signal component is -. (1 horizontal scanning period) only changes from the previous signal to -, and even if the mixing circuit 14 is changed, the amount of the original signal component does not change to -. Therefore, this first frequency selection circuit can be easily realized in the form shown in FIG.

26 is a frame memory, and 27 is a 1H memory.

Furthermore, since it is only necessary to extract the luminance signal, it is extremely easy to handle matters other than frequency selection.

For example, when image quality improvement such as noise reduction or scanning line interpolation is to be performed, the first frequency selection circuit 5 may be expanded as shown in FIG.

In FIG. 8, 28 is a first delay circuit, 29 is a fourth addition circuit, 30 is a 263H memory, 31 is a 262H memory, 32 is a second polarity inversion circuit, 33 is a third addition circuit, 5
4 is a first low-pass filter, 35 is a nonlinear circuit, 66
37 is the second delay circuit, 37 is the sixth addition circuit, 58 is the motion detection circuit, 39 is the second low-pass filter, and 40 is the third
This is the output circuit.

The delay circuit 28 of the well 1 is connected to the second polarity reversing circuit 32°.
Addition circuit 33. Low pass filter 34. Nonlinear circuit 3
This is to correct the delay time that occurs in step 5. 26
The 2H memory 31 is actually busy with the third addition circuit 33. Low pass filter 34. Nonlinear circuit 35. The delay time caused by the addition circuit 29 of IE4 is shorter than 262H.

The nonlinear circuit 35 adjusts the coefficient depending on the level difference so that when the level difference between the current signal and the previous frame signal is small, more of the previous frame signal is fed back, and when the level difference is large, less of the previous frame signal is fed back. With a changing multiplication circuit,
This is, for example, ROM (Read Qnly Memo
ry: read-only memory). This fourth adder circuit 29.26
3H memory 30°262H memory 51. Third addition circuit 33. second polarity inversion circuit 32, first low-pass filter 34. The nonlinear circuit 35 constitutes a feedback type noise reduction circuit using frame correlation. The second delay circuit 36 is for correcting the fact that the 262H memory is slightly shorter than 262H and obtaining the difference between the output of the fourth adder 29 and one frame, and the output of this second delay circuit is ,m
This corresponds to the output of the frame memory 26 in FIG. Therefore, using this output and the 1H memory 27 output, the polarity inverting circuit 18. First addition circuit 19. High pass filter 20. Switch circuit 25. From the third addition circuit 24,
A circuit corresponding to the first frequency selection circuit 5 shown in FIG. 7 will be realized. Since the inter-frame difference is obtained by the sixth addition circuit, the motion detection circuit 38 passes this through a low-pass filter and takes the absolute value to extract the amount of motion, and the mixing circuit 14 is controlled.

The second scanning line interpolation signal for increasing the vertical resolution by increasing the density of scanning lines is, for example, the luminance of one field before the color signal obtained by passing the 263H mesori output through the second low-pass filter 59. All you have to do is use a signal. In this way, a part of the frame comb-shaped frame memory can also be used for field delay between scanning lines.

In order to improve the image quality by making the interpolation signal even higher in resolution, the interpolation signal may be turgorically compressed as shown in FIG.

41 is the third input terminal, 42 is the second 1H memory ζ・4
3 is the second 262H memory, 44 is the seventh adder circuit, 4
5 is a Wt2 mixing circuit, and 46 is a sixth output terminal.

A broadband luminance signal from which the color difference signal from the third output terminal 11 has been removed is input to the third input terminal 41 .

The output of the second 1H memory 42 and the signal averaged by the adder circuit 44 of wL7, the output of the second 1H memory 42 and the second 2
62H memory 43 simply creates a class 21II signal which is a signal delayed by 263H, and a second mixing circuit 45 controls the mixing ratio of these two types of signals according to the amount of motion, and generates a 6th class signal as an interpolation signal. It is output from the output terminal 46 of.

This interpolation signal is used for interpolation as a signal of the scanning line between the scanning lines output from the third output terminal 11. In this way, the interpolated signal also becomes a wideband signal.

Furthermore, in the example of FIG. 8, noise removal could only be applied to the low-frequency components of the luminance signal, but in order to apply this to the entire band, it is sufficient to do as shown in FIG. 10.

In FIG. 10, 47 is the third mixing circuit, and 48 is the eighth mixing circuit.
adder circuit, 49 is @2 263H memory, 5 (1 is m
3 262H memory, 51 a subtraction circuit, 52 a second nonlinear circuit, 53 a third 1H memory, 54 a ninth addition circuit, 55 an flL4 mixing circuit, 56 an eighth output terminal, 57 is the ninth output terminal. second frame comb 22, g2 line comb 23, first mixing circuit 14
Then, detect unnecessary color signal components in the same manner as in Figure 3,
The high-pass filter 20 removes the color signal outside the band, and the detected unnecessary color component is mixed with the original signal via the switch 25 to produce the luminance signal from which the unnecessary color signal has been removed. obtain. After that, the eighth adder 48° second 263H
Feedback type noise removal using frame correlation is constituted by a third 262H memory, a subtraction circuit 511, and a second nonlinear circuit 52. In this way, since the chrominance signal has already been removed, noise can be reduced over the entire signal band of the luminance signal, making it possible to significantly improve the S/N ratio. Rather than using the average of the third 1H memory output and the eighth adder output as an interpolation signal for moving images, this second 263H memory output is used as an interpolation signal when stationary, and the mixing ratio is adaptively adjusted according to movement. An interpolated signal is taken out from the eighth output terminal 56 as the output of the third mixer 55, which is controlled, and is displayed alternately with the output signal from the ninth output terminal 57 line by line.

Although the first frequency selection circuit 5 has been described above, similar processing is also possible for the fR3 frequency selection circuit 7 that removes unnecessary luminance signals. That-
An example is shown in FIG.

In FIG. 11, 58 is a seventh input terminal, 59 is a bandpass filter, 60 is an ACC amplifier circuit, 61 is a color signal demodulation circuit, 62 is a third delay circuit, 63 is a tenth addition circuit, and 64 is a Frame memory, 65 is m11 addition circuit,
66 is a sixth nonlinear circuit, 67 is a third polarity inversion circuit,
68 is the 1H memory, 69 is the third mixing circuit, and 70 is the second
, 71 is the twelfth adder circuit, 72 is the first switch circuit, and 71 is the twelfth adder circuit.
0 output terminal 73 is a fourth delay circuit.

The digital composite signal inputted from the seventh input terminal 59 is filtered by a bandpass filter 59 to remove low frequency components that do not contain color signals, and then sent to an ACC amplifier circuit 6.
At 0, the burst is amplified to a constant level.

Here, the frequency (-4fsa) + 4 times the color subcarrier
For example, (RY), (B-Y), (-(R-Y)) (-(B-
Y)), so if you reverse the polarity every two data, each sample becomes [(FL-Y) and (
A signal is obtained in which the detected color difference signals (B-Y) are alternately multiplexed for each sample.

Therefore, this signal is passed directly to the third delay circuit 62 and the first delay circuit 62.
The signal is input to the frame memory 64 via the 0 addition circuit 63. This frame memory 64 is actually slightly shorter than the i frame (ie, 525H) by the delay time caused by the 11th addition circuit, the third nonlinear circuit 66, and the 10th addition circuit 63. The output of this frame memory 64 is m3
The signal is subtracted by a subtraction circuit composed of a polarity inversion circuit 67 and an eleventh addition circuit 65, and the difference between the signal and the signal before the frame delay is calculated. When this difference is small, the coefficient is large and the feedback amount is large; when the difference is large, the coefficient is small and the feedback amount is small. The signals are added together and a noise removal operation is performed. In this case, it is possible to achieve a good improvement over the entire band, and a large S/N improvement can be achieved.

Thereafter, the signal delayed by one frame in the fourth delay circuit 73 of the frame memory 64 and the 1H memo 1 Noro 8 output are mixed in a third mixing circuit whose mixing ratio is adaptively controlled according to the amount of movement. , are added to the original signal via the switch circuit 70. When the original signal is a component signal that does not include a luminance signal, this switch circuit 70 is turned off and the frequency selection operation is stopped. For still images, only the one frame delayed signal is added to the original signal, so frame combing is performed. When the amount of motion is large, only the 1H delayed bone is added to the original signal, so line combing is performed.

In this way, a frequency selection operation for adaptively removing unnecessary luminance signals can be realized. For still images, frame combing is possible and a complete luminance signal removal power of 1 is possible.

Furthermore, when the color signal is detected, two color difference signals (for example, I
and Q, or (RY) and (B-Y)), and noise removal and unnecessary luminance signal component removal may be performed on each of them independently.

In this case, it can be realized, for example, in the form shown in FIG.

In FIG. 12, 74 is a first unnecessary signal removal circuit;
5 is the third delay circuit, 76 is the addition circuit of m13, 77 is the frame memory, 78 is the 14th addition circuit, and 79 is the fourth addition circuit.
, 80 is a polarity inversion circuit, 81 is a sixth delay circuit, 82 is a 1H memory, 83 is a sixth mixing circuit, 84
is a switch circuit, 85 is a 16th adder circuit, 86 is an IE
2, an unnecessary signal removal circuit 87, a 12th output terminal 87, and a color difference demodulation circuit 89 outputting two color difference signals from separate terminals.

tILl no fuii! The inside of the signal rejection circuit has exactly the same configuration as the corresponding part in FIG.
In the case shown in the figure, it is a multiplex signal of (RY) and (B-Y) (or a multiplex signal of E and Q), but only one of these is input.The operation is shown in Figure 11. is exactly the same. Furthermore, the second unnecessary signal removal circuit 86 may be exactly the same as the first unnecessary signal removal circuit.

It is clear that the scanning line interpolation for color signals can be easily carried out by using a circuit as shown in FIG.

As explained above, by using Fig. 8, Fig. If the signal is inputted from before the first frequency selection port 5 in FIG. 2, and the color signal is inputted from the output part of the second frequency selection circuit 6, it will be extremely easy to input the 7-lease component signal. I can handle it. Also, for composite signals, t and -C are set to MK so that there is no need to consider the phase of color subcarriers in the frame memory part, so one frame freeze can be handled extremely easily. .

〔Effect of the invention〕

As explained above, according to the present invention, first, the luminance signal and the chrominance signal are roughly separated, and then Lτ is applied to each, and unnecessary signals are further removed, resulting in high image quality such as YC separation and noise removal. At the same time, it has the effect of making it easier to respond to higher functionality, such as making it easier to handle freezes and component signals.

[Brief explanation of drawings]

FIG. 1 is a diagram showing one embodiment of the present invention, FIG. 2 is a diagram showing another embodiment of the present invention, FIG. 3 is a diagram showing an embodiment of the frequency selection circuit portion of the present invention, and FIG. The figure shows a second embodiment of the frequency selection circuit portion of the invention, FIG. 3 shows a third embodiment of the frequency selection circuit portion of the invention, and FIG. 6 shows the frequency selection circuit of the invention. Figure 1 showing a fourth embodiment of the part
Figure 1R7 shows a third embodiment of the frequency selection circuit portion of the present invention, Figure '88 shows a sixth embodiment of the frequency selection circuit portion of the present invention, and Figure 9 shows a signal for scanning line interpolation. 10 is a diagram showing a seventh embodiment of the frequency selection circuit portion of the present invention, and FIG. 11 is a diagram showing an example of the frequency selection circuit of the color signal processing circuit portion of the present invention. 12 are diagrams showing other embodiments of the frequency selection circuit of the color signal processing circuit portion of the present invention. Explanation of symbols 4...AD converter, 5, 6.7.9...Frequency selection circuit, 12.22...
・Frame comb shape, 12.23... Line comb shape, 18, 26. (54, 77... frame memory, 8
... Color difference signal demodulation circuit, 14, 69.83 ... Mixing circuit, 19, 21.24.71.85 ... Addition circuit, 27,
73.82... line memory, 25, 70.84...
・Switch. 17... Polarity inversion circuit, 20... High frequency pass filter, 30... 263H memory, 31... 262H memory, 32... Delay circuit. ／″飄(、＊－'、、、）' j

Claims (1)

[Claims] 1. An AD converter that quantizes a composite signal in which a color signal is multiplexed on a high frequency band of a luminance signal, and an AD converter that extracts a frequency band in which the color signal is multiplexed from the output of the AD converter. a second frequency selection circuit for removing a color signal from the output of the AD converter; and a third frequency selection circuit for further removing a luminance signal component from the output of the first frequency selection circuit. A digital television receiver comprising a frequency selection circuit. 2. The digital television receiver according to claim 1, characterized in that the second frequency selection circuit includes a frame comb that calculates the sum between one frame. 3. The digital television receiver according to claim 1, characterized in that a color difference signal demodulation circuit is provided between the first frequency selection circuit and the third frequency selection circuit. 4. A frequency selection circuit for extracting unnecessary components whose frequency selection characteristics can be varied according to the amount of movement of the composite signal, at the subsequent stage of the AD converter that quantizes the composite signal obtained by multiplexing the color signal on the high frequency band of the luminance signal. A signal selection circuit including a mixing circuit that mixes an output with an original signal to remove unnecessary components, characterized in that a switch is provided between the frequency selection circuit and the mixing circuit. The digital television receiver according to item 1.