JP2001008120A - Image synthesis circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To synthesize an HDTV signal and an HD graphics signal without using a very high speed digital element. SOLUTION: The image synthesis circuit 10 is provided with input terminals 1, 4, an NTSC/HDTV discrimination part 18, 1st to 3rd switches SW1 to SW3, a format conversion part 2A, a frame synchronization part 3, and a synthetic part 5. An NTSC signal or an HDTV signal is inputted to the 1st input terminal 1, whether the input signal is the NTSC signal or the HDTV signal is discriminated by the discrimination part 18 and the 1st to 3rd switches SW1 to SW3 and a switch part 23 in the conversion part 2A are switched to the (a) side or (b) side in accordance with the discriminated result. When an NTSC signal is inputted to the input terminal 1, respective switches are switched to the (a) side and the input signal is converted into an HDSC format by the conversion part 2A, synchronized with an HD graphics signal, returned to an analog signal, and then synthesized with the HD graphics signal. When an HDTV signal is inputted to the input terminal 1, respective switches are switched to the (b) side, only the digital conversion of the input signal is executed by the conversion part 2A and the digital signal is synchronized with the frame synchronization part 3 and returned to an analog signal, which is synthesized with the HDTV signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention makes it possible to combine a high-definition television signal (hereinafter referred to as HDTV signal) with a high-definition text / graphics signal (hereinafter referred to as HD graphics signal) for display. To a video synthesis circuit.

[0002]

2. Description of the Related Art In a television receiver, an HDTV signal system has been developed to improve image quality. H
The screen of the DTV signal system is composed of 1125 scanning lines in a two-to-one interlace, and its luminance signal band is 20 MHz or more (maximum 30 MHz) and the conventional NTN.
There are several times that of the SC system, and fine and high-definition image quality can be obtained. Further, in the HDTV signal system, the frequency band is wide due to the large amount of information, and for example, a band compression system called the MUSE system has been developed from the economical efficiency of broadcast radio waves. This is a broadband HDT over 20 MHz
The V signal is band-compressed to about 8 MHz so that it can be broadcast on only one channel of satellite broadcasting.

The HDTV signal system has a frame frequency of 30H.
z, 1125 scanning lines, aspect ratio 16: 9, for example, a luminance signal band obtained by decoding a MUSE signal is about 20 MHz. On the other hand, the conventional NTSC system has a frame frequency of 30 Hz, 525 scanning lines, an aspect ratio of 4: 3, and a luminance signal band of about 6 MHz.

[0004] Some television receivers that support HDTV signals convert conventional NTSC signals into HDTV signal format and project the signals. As such a television receiver, for example,
There is one described in Japanese Patent Application No. 8-253514 by the present applicant.

By unifying the NTSC signal into the HDTV signal format, there are advantages such as i) the use of a single deflection circuit, and ii) improvement in the resolution of the still image portion of the NTSC signal depending on the conversion method. .

On the other hand, in such a television receiver, a high-definition HD graphics signal is combined with a video signal (superimposition) for taking advantage of the high-definition characteristic, for example, for selecting a channel or guiding an operation method. That is being done. Examples of such HD graphics signals include those used in decoders for receiving satellite or terrestrial digital broadcasts in North America and the like.

FIG. 3 shows a configuration of a video synthesizing circuit for synthesizing an NTSC signal and an HD graphics signal in a conventional HDTV compatible television receiver.

In FIG. 3, analog NTSC signals and HD graphics signals are input to input terminals 1 and 4, respectively.

[0009] The NTSC signal applied to the input terminal 1 is converted to an HDTV signal via a format conversion unit 2 and then input to a frame synchronization unit 3.

The format converter 2 includes an A / D converter 21 for converting an input analog NTSC signal into a digital signal, and a memory (for example, a line memory) for storing a video signal, and converts the digital NTSC signal into an HDTV signal format. And a format conversion unit 22 for converting and outputting. The system conversion unit 22 reads out the digital data written in the memory at a speed 15/7 times as fast as the writing, and generates an interpolation line, so that the time is 7/1 in time.
5, the converted frequency bandwidth is 15/7.
(This is based on 1125: 525 = 15: 7).

The HD graphics signal applied to the input terminal 4 is guided to the synthesizing section 5 and simultaneously the frame synchronizing section 3
Is also used as a reference for video synchronization. That is, the frame synchronization unit 3 synchronizes the frame of the NTSC signal converted into the HDTV signal with reference to the HD graphics signal.

The frame synchronizing unit 3 includes a memory (eg, a frame memory) for storing video signals, and synchronizes the NTSC signal, which has been converted into the HDTV signal, with the synchronizing signal from the synchronizing signal generator 32. 31 and H
A synchronizing signal generator 32 for generating a synchronizing signal corresponding to the D graphics signal; and a D / D converter for converting the digital NTSC signal synchronized by the synchronizing unit 31 into an analog signal and outputting the analog signal.
And an A conversion unit 33.

The NTSC synchronized by the frame synchronization unit 3
The signal and the HD graphics signal from the input terminal 4 are added together, for example, by the synthesizing unit 5, and an output terminal 6 outputs a video signal in HDTV format. In the synthesizing unit 5, two signals are synthesized and output in an analog signal state.

The video signal band of the conventional NTSC signal is at most 6 MHz, and that of the double-speed NTSC signal is twice that of 12 MHz. Normally, the format converter 2 and the frame synchronizer 3 perform signal processing by digital technology, and the sampling clock for digitally converting the NTSC signal is 4 fsc (where fsc is the frequency of the chrominance carrier, and 4 times as large as the frequency). About 14.3 MHz). Alternatively, the sampling clock of the doubled NTSC signal is 8 fsc (about 28.6 MHz), and the original video signal can be converted into a digital signal without deteriorating the quality. Further, the read clock of the format conversion unit 22 is 4 fsc × (15 /
7) is about 30.7 MHz.

In the above-described video synthesizing circuit, the case where the NTSC signal is synthesized with the HD graphics signal through the video synthesizing circuit has been described. However, in the above-described video synthesizing circuit, if an HDTV signal is supplied to the input terminal 1 instead of the NTSC signal, and the HDTV signal is synthesized, the video signal bandwidth of the HDTV signal is about 3 at maximum.
Since there is 0 MHz, the sampling clock requires 60 MHz or more. This is twice or more the operating speed as when an NTSC signal is input to the input terminal 1, and an ultra-high-speed digital device for format conversion is required. When an ultra-high-speed digital element is used, problems such as an increase in heat generation, an increase in spurious power, and an increase in cost are caused.

[0016]

SUMMARY OF THE INVENTION As described above, HDTV
In order to combine the signal with the HD graphics signal, the HD
When a TV signal is passed through the same video synthesizing circuit as in the case of the NTSC signal, an ultra-high-speed digital element is required, which causes an increase in heat generation, an increase in spurious power, and an increase in cost.

Accordingly, the present invention has been made in view of the above problems, and
After converting the SC signal to the HDTV signal format,
In addition to the function of synthesizing with the D graphics signal, the HDTV signal and the HD
It is an object of the present invention to provide a video synthesizing circuit capable of synthesizing graphics signals.

[0018]

According to a first aspect of the present invention, there is provided a video synthesizing circuit comprising: a first input terminal to which an NTSC signal or an HDTV signal is input as a first video signal;
A second input terminal to which an HD graphics signal is input as a video signal, and an NTSC signal as a first video signal to the first input terminal (hereinafter referred to as a first video signal).
), The NTSC signal is selected, and when the HDTV signal is input to the first input terminal as the first video signal (hereinafter, the second case), the NTSC signal is input to the second input terminal. A first switch for selecting the added HD graphics signal, and converting an output signal selected by the first switch into an HDTV signal format as required, wherein Converts the NTSC signal output from the first switch into an HDTV signal format, and in the second case, passes through the HD graphics signal output from the first switch without format conversion. A conversion unit for selecting one of the signals to be synthesized, and in the first case, the HD signal from the second input terminal.
A second switch for selecting a graphics signal and, in the second case, an HDTV signal from the first input terminal; and a second switch for selecting a synchronization reference signal. , The HD from the second input terminal
A graphics signal is selected, and in the second case, a third switch for selecting an HDTV signal from the first input terminal and an output signal of the format conversion unit are selected by the second switch. In the first case, the HDTV format-converted NTSC signal output from the format conversion unit is converted to an HD graphics signal from the third switch. In the second case, the HD graphics signal output from the format conversion unit is synchronized with the HDTV signal from the third switch, and the frame input unit is input to the first input terminal. It is determined whether the first video signal to be output is an NTSC signal or an HDTV signal, and the first, second, and third switches are switched based on the determination result. NTSC / HD switching the necessity of format conversion at Utotomoni the format converter
A TV discriminating section; and a synthesizing section for synthesizing an output signal from the frame synchronizing section and an output signal from the second switch.

According to the first aspect of the present invention, first to third selection switches are provided at an input terminal of the format conversion unit, one input terminal of the synthesizing unit, and a reference signal input terminal of the frame synchronizing unit, respectively. With the circuit configuration, NTSC signals can be converted to HD using the same video synthesis circuit as before.
In addition to the function of synthesizing with the HD graphics signal after converting to the TV signal format, a video synthesizing circuit having a function of synthesizing the HDTV signal and the HD graphics signal without using an ultra-high-speed digital element can be realized.

According to a second aspect of the present invention, in the video synthesizing circuit according to the first aspect, the format converter includes an A / D converter for converting an input analog NTSC signal or HD graphics signal into a digital signal. And a memory for storing the video signal, and the digitally converted N
A system converter for converting a TSC signal into an HDTV signal format and outputting the same, and a switch interposed between the A / D converter and the system converter, wherein a digital signal from the A / D converter is When the signal is an NTSC signal, the NTS signal
The C signal is guided to the format conversion unit, and when the digital signal from the A / D conversion unit is an HD graphics signal, the HD graphics signal is passed through the format conversion unit and sent to the next-stage frame synchronization unit. A switch unit for guiding the video signal, the frame synchronization unit includes a memory for storing a video signal, and the format conversion unit converts the digital NTSC signal into an HDTV signal format, or the format conversion unit. A synchronizing unit for synchronizing the digital HD graphics signal subjected to only the A / D conversion with reference to the signal selected by the third switch, and an HD graphics signal or HD from the third switch.
TV signal input, HD graphics signal or HDT
A synchronization signal generator for generating a synchronization signal corresponding to the V signal, a D / A converter for converting a digital NTSC signal or a digital HD graphics signal synchronized by the synchronization unit into an analog signal and outputting the analog signal; It is characterized by having.

[0021]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an HD according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a video synthesizing circuit in a TV compatible television receiver, and FIG. 2 is an image diagram of the television receiver in FIG. The same elements as those in FIG. 3 are described with the same reference numerals.

First, a description will be given with reference to the image diagram of FIG. H
The DTV-compatible television receiver 20 has an analog H
A set-top box (hereinafter, referred to as STB) 11 for receiving and demodulating (including descrambling) a DTV broadcast signal via a cable (CABLE) is connected.
The HDTV signal is demodulated by the HDTV STB 11 and supplied to one input terminal of the selector 13 in the receiver 20. The receiver 20 is connected to antennas ANT1, ANT2, and ANT3 for receiving terrestrial analog broadcasting, satellite digital broadcasting, and terrestrial digital broadcasting, in addition to a cable (CABLE) for HDTV reception. Receiver 2
0, a tuner 12 for receiving and demodulating a terrestrial analog TV broadcast signal, a satellite digital broadcast (including satellite data broadcast), and a terrestrial digital broadcast HDT.
An HDTV digital decoder 16 for receiving and demodulating the V signal is provided, and the output of the tuner 12 is supplied to the other input terminal of the selector 13. HDT
The V digital decoder 16 can supply the decoded output to the display device 19, and generates an HD graphics signal in the HDTV digital decoder 16 (see FIG. 1).
Can generate an HD graphics signal.
The HD graphics signal generator receives various control signals from a microcomputer (not shown) in the decoder 16 and outputs a high-definition signal (ie, H) of a character or a picture according to the control signals.
D graphics signal), and the generated H
The D graphics signal is supplied to the video composition circuit 10,
The analog signal (HDTV signal or NTSC signal) selected by the user operation by the selector 13 is combined and supplied to the display device 19.

Next, FIG. 1 will be described. The analog HDTV signal transmitted via the cable (CABLE) is received and demodulated by the HDTV STB 11 and supplied to the first input terminal of the selector 13. Also, antenna ANT1
The terrestrial analog TV broadcast signal (NTSC signal) input to the tuner 12 is received and demodulated by the tuner 12 and
Is supplied to a second input terminal. HDTV is connected to the third and fourth input terminals 14 and 15 of the selector 13, respectively.
HDTV and NTSC video signals can be externally input from external devices for TV and TV (for example, a recording / reproducing device such as a VTR).

Therefore, the selector 13 includes the S for HDTV.
Two signals of the HDTV system from the TB 11 and the input terminal 14 and two signals of the NTSC system from the tuner 12 and the input terminal 15 can be input. ) Allows one signal to be selected and output.

On the other hand, each digital TV broadcast signal of satellite digital and terrestrial digital from each of the antennas ANT2 and ANT3 is received and demodulated by the HDTV digital decoder 16 and can be supplied to the display device 19, while the internal HD graphic is The signal generation unit 17 outputs an HD graphic of characters and pictures in response to a control signal from a microcomputer (not shown) provided in the decoder 16 (for example, a control signal for instructing channel display at the time of channel switching or displaying help information). Signal can be generated. In addition, the HD graphics signal generation unit 17 uses an HDTV
It is also possible to generate independent data that is not directly related to digital broadcast channels and programs received by the digital decoder 16. Therefore, STB for HDTV
It is also possible to generate the channel display data in synchronization with the channel switching of the analog broadcast by the tuner 11 or the tuner 12. In other words, the HD graphics signal generator 17 has a function of generating character graphics necessary for displaying a channel or help when receiving digital broadcasting by the HDTV digital decoder 16,
It also has a function of generating character graphics necessary for channel display, help display, and the like at the time of analog broadcast reception by the V STB 11 and the tuner 12.

The analog video signal (HDTV signal or NTSC signal) selected by the selector 13 is supplied to the input terminal 1 of the video synthesizing circuit 10. In addition, the HD
The HD graphics signal from the graphics signal generator 17 can be supplied to the input terminal 4.

The video synthesizing circuit 10 includes first and second input terminals 1 and 4, an NTSC / HDTV discriminating unit 18,
Second and third switches SW1, SW2, SW3, a format converter 2A, a frame synchronizer 3, and a synthesizer 5
And an output terminal 6.

A first input terminal 1 receives an analog NTSC signal or HDT signal from a selector 13 as a first video signal.
The V signal is input, and an analog HD graphics signal is input to the second input terminal 4 as a second video signal.

The NTSC / HDTV discriminating section 18 receives the video signal selected by the selector 13, separates the synchronizing signal from the video signal, and separates the synchronizing signal frequency (NTSC
15.75 kHz for signal, 33.7 for HDTV signal
5 kHz) to determine whether the signal is NTSC or HDT.
V is determined, and a high-level and low-level determination signal indicating the determination result is output.

The first video signal from the first input terminal 1 is input to one input terminal a of a first switch SW1, while one input terminal b and third input terminal b of a second switch SW2.
Is input to one input terminal b of the switch SW3. The second video signal from the second input terminal 4 is input to the other input terminal b of the first switch SW1, while the other input terminal a of the second switch SW2 and the third switch SW3.
Is input to the other input terminal a. Each of the first to third switches SW1 to SW3 is such that the input terminals a and b can be switched by a discrimination signal from the NTSC / HDTV discriminating unit 18, and the discrimination signal indicates a HDTV signal (for example, a high signal). Level signal), each switch SW1
SW3 are simultaneously switched to the input terminal b, and when the discrimination signal is a signal indicating the NTSC signal (for example, a low level signal), each of the switches SW1 to SW3 is simultaneously switched to the input terminal a.

Either the NTSC signal applied to the input terminal 1 or the HD graphics signal applied to the input terminal 4 is input to the format converter 2A through the first switch SW1, where the NTSC signal is input. In the case of, the format is converted to an HDTV signal, and then supplied to the frame synchronization unit 3.

The format converter 2A includes an A / D converter 21 for converting an input analog NTSC signal or HD graphics signal into a digital signal, and a memory (for example, a line memory) for storing a video signal. A format converter 22 for converting the digitally converted NTSC signal into an HDTV signal format and outputting the converted signal;
A switch interposed between the conversion unit 21 and the system conversion unit 22. When the digitally converted signal from the A / D conversion unit 21 is an NTSC signal, the NTSC signal is converted to the system conversion unit 22. When the digital signal from the A / D conversion unit 21 is an HD graphics signal, a switch for guiding the HD graphics signal through the format conversion unit 22 to the frame synchronization unit 3 at the next stage. And a unit 23. The switch unit 23 includes an output terminal a for leading the output of the A / D conversion unit 21 to an input terminal of the system conversion unit 22 and an output terminal a for converting the output of the A / D conversion unit 21 to the system conversion unit 22.
And an output terminal b for guiding the signal to the output terminal of the format conversion unit 22 without passing through the switching unit 22 in accordance with a determination signal from the NTSC / HDTV determination unit 18. Therefore, the output terminals a and b of the switch unit 23 are also connected to the terminal a when the output of the selector 13 is an NTSC signal and the output of the selector 13 is connected to the HDTV simultaneously with the switching of the first to third switches SW1 to SW3. If it is a signal, it is switched to terminal b. The format conversion unit 22 reads out the digital NTSC signal written in the video memory at a speed 15/7 times that at the time of writing, and generates an interpolation line to temporally compress the signal to 7/15. Therefore, the frequency bandwidth after format conversion is 15/7 times.

The frame synchronizing unit 3 includes a memory (eg, a frame memory) for storing a video signal, and a digital NTSC signal converted to an HDTV signal format by the format converting unit 2A or a format converting unit 2
A synchronizing unit 31 for synchronizing the digital HD graphics signal subjected to A / D conversion only in A with a synchronizing signal from a synchronizing signal generating unit 32 and outputting the HD graphics signal or HDTV signal from a third switch SW3 And enter H
A synchronizing signal generating unit 32 for generating a synchronizing signal corresponding to a D graphics signal or an HDTV signal; and a digital NTSC signal or digital H synchronized by the synchronizing unit 31.
The D / A converter 33 converts a D graphics signal into an analog signal and outputs the analog signal.

Therefore, when the NTSC signal is selected by the selector 13, the NTSC signal supplied to the input terminal 1 is format-converted by the format converter 2A, synchronized by the frame synchronizer 3, and multiplexed by one of the synthesizers 5. The HD graphics signal guided to the input terminal and applied to the input terminal 4 is guided to the synchronizing signal generating unit 33 of the frame synchronizing unit 3 to be used as a reference for video synchronization and to the other input terminal of the synthesizing unit 5 at the same time. I will That is, when the NTSC signal is selected by the selector 13, the frame synchronization of the NTSC signal converted into the HDTV signal format is performed by the frame synchronization unit 3 based on the HD graphics signal.

When the HDTV signal is selected by the selector 13, the HD graphics signal applied to the input terminal 4 is guided to the format converter 2A (actually, the format converter 22 is passed through). The HDTV signal synchronized at 3 and supplied to one input terminal of the synthesizing unit 5 and supplied to the input terminal 1 is guided to the synchronizing signal generating unit 32 of the frame synchronizing unit 3 and used as a reference for video synchronization. The signal is guided to the other input terminal of the synthesizing unit 5. That is, when the HDTV signal is selected by the selector 13, the frame synchronizing unit 3 synchronizes the frame of the HD graphics signal with the HDTV signal as a reference.

The NTSC signal and the HD graphics signal synchronized with the HD graphics signal by the frame synchronization unit 3 or the HD graphics signal and the HDTV signal synchronized with the HDTV signal by the frame synchronization unit 3 are as follows. For example, the two signals are added by the synthesizing unit 5 and the output terminal 6
Output from In the synthesizing unit 5, the two signals are synthesized and output in the state of the analog signal. The combined signal from the output terminal 6 is supplied to the display device 19 and displayed on the HDTV. At this time, the synchronization signal used in the display device 19 is an HD graphics signal or an HDT signal supplied to the frame synchronization unit 3 as a reference for video synchronization.
The synchronization signal of the V signal will be used.

When the digital broadcasting signal demodulated by the HDTV digital decoder 16 is displayed on the display device 19, a synchronizing signal obtained from the signal demodulated by the HDTV digital decoder 16 is used as the synchronizing signal. Of course.

Next, the operation of the video synthesizing circuit 10 in FIG. 1 will be described. When the “a” side is selected by the first to third switches SW1 to SW3 and the switch unit 23, the NTSC
This corresponds to the case where the signal and the HD graphics signal are combined, and the case where the b side is selected corresponds to the case where the HDTV signal and the HD graphics signal are combined.

(1) When the output of the selector 13 is an NTSC signal, that is, when each switch is selected to the a side, the circuit operation is the same as that of FIG. In this case, analog NTSC signals and HD graphics signals are input to the input terminals 1 and 4, respectively. The NTSC signal applied to the input terminal 1 is converted into a digital signal and an HDTV signal format via a format converter 2A, and then input to a frame synchronizer 3.

On the other hand, the HD graphics signal applied to the input terminal 4 is guided to the synthesizing unit 5 and is also applied to the frame synchronizing unit 3 to be used as a reference for video synchronization.

In the frame synchronization section 3, the NTSC signal converted into the HDTV signal format is frame-synchronized with the HD graphics signal as a reference, converted into an analog signal, and output.

The analog NTSC signal synchronized with the HD graphics signal by the frame synchronization section 3 is input to an input terminal 4.
Are added to the analog HD graphics signal from the synthesizing unit 5 and output from the output terminal 6 as a synthesized video signal in the HDTV format.

(2) When the output of the selector 13 is an HDTV signal, that is, when each switch is selected to the b side, the analog HDTV signal applied to the input terminal 1 is subjected to the second conversion without any conversion. To the one input terminal of the synthesizing unit 5 through the switch SW2. On the other hand, the analog HD graphics signal applied to the input terminal 4 is guided to the format converter 2A via the first switch SW1. The HD graphics signal input to the format converter 2A is converted into a digital signal by an internal A / D converter 21. Here, the number of horizontal pixels of the high definition HD graphics signal is about 480. Therefore, if a sampling clock of 960 times or more of the horizontal frequency (about 33.75 kHz) is used, the quality can be maintained even when digitized. By the way, if it is set to 960 times the horizontal frequency, it is about 32.4 MHz, which is doubled NTSC
This is not much different from the signal sampling clock of about 28.6 MHz. That is, when digitizing an HD graphics signal, an ultra-high speed (in this case, a sampling clock 70
A digital element that does not require a digital element (which requires more than MHz) and has a necessary speed when digitizing the double-speed NTSC signal described with reference to FIG.

In the format converter 2A, since the HD graphics signal is in the HDTV signal format,
It is not necessary to perform format conversion only by converting the HD graphics signal into a digital signal by the A / D conversion unit 21, and therefore, the signal is passed through the system conversion unit 22 by the switch unit 23 and is guided to the frame synchronization unit 3 in the next stage. In the frame synchronizing unit 3, the HD supplied through the third switch SW3
Using a TV signal as a reference for video synchronization, synchronization of a digital HD graphics signal is achieved. The HD graphics signal synchronized by the frame synchronization unit 3 is returned to an analog signal by the D / A conversion unit 33 inside the frame synchronization unit 3 and supplied to the other input terminal of the synthesis unit 5. The synthesizing unit 5 adds the analog HDTV signal and the synchronized analog HD graphics signal, synthesizes the resultant signal, and guides the resultant signal to the output terminal 6, thereby providing a video in which the HDTV signal and the HD graphics signal are synthesized. A signal can be obtained.

In the above-described embodiment, the NTSC
Although the video synthesizing circuit in the HDTV compatible television receiver for converting the signal into the HDTV signal format and projecting the same has been described, in the present invention, not only the NTSC signal but also other standard color television signals such as the PAL signal and the SECAM signal are used. The present invention can also be applied to an HDTV-compatible television receiver which converts an image into an HDTV signal format and projects the image.

[0046]

As described above, according to the present invention, NT
In addition to combining the SC signal converted to the HDTV signal format with the HD graphics signal, the HDTV signal and the HD graphics signal can be combined using almost the same video combining circuit. Moreover, since an ultra-high-speed digital element is not required, there is no possibility that problems such as an increase in heat generation, an increase in spurious power, and an increase in cost will occur.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a video synthesizing circuit in an HDTV-compatible television receiver according to an embodiment of the present invention.

FIG. 2 is a diagram showing an image configuration of an HDTV-compatible television receiver equipped with the video synthesizing circuit of FIG. 1;

FIG. 3 is a block diagram showing a conventional video synthesizing circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 1st input terminal 2A ... Format conversion part 3 ... Frame synchronizing part 4 ... 2nd input terminal 5 ... Synthesis part 6 ... Output terminal 18 ... NTSC / HDTV discrimination part 21 ... A / D conversion part 22 ... System conversion Section 23 Switch section SW1 First switch SW2 Second switch SW3 Third switch

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) DD03 DD07 ED04 EE11 EF01 GA12 GA22 GB01 KD06 KE02 KE07 KE19 KE20 KG01 KM11 LA02 5C082 BA12 BA27 BA41 CA55 CA84 CB01 DA51 MM04 MM07

Claims (2)

[Claims] 1. An NTSC signal or an H signal as a first video signal.
A first input terminal to which a DTV signal is input; a second input terminal to which an HD graphics signal is input as a second video signal; and an NTSC signal as a first video signal to the first input terminal. When input (hereinafter, the first case), the NT
When an SC signal is selected and an HDTV signal is input to the first input terminal as a first video signal (hereinafter, referred to as a second video signal).
Case), a first switch for selecting the HD graphics signal applied to the second input terminal, and an output signal selected by the first switch is converted into an HDTV signal format as necessary. To convert,
In the first case, the NTSC signal output from the first switch is converted into the HDTV signal format, and in the second case, the H level output from the first switch is changed to H.
A format converter for passing through the D graphics signal without format conversion, and for selecting one signal to be synthesized,
In the first case, the HD graphics signal from the second input terminal is selected, and in the second case, the HD graphics signal is selected.
And a second switch for selecting an HDTV signal from an input terminal of the second terminal. A second switch for selecting a synchronization reference signal. In the first case, an HD graphics signal from the second input terminal is And, in the second case, a third switch for selecting an HDTV signal from the first input terminal; and an output signal of the format conversion unit, which is to be synthesized by the second switch. In the first case, the HDTV format-converted NTSC signal output from the format conversion unit is synchronized with the HD graphics signal from the third switch, and In the second case, a frame synchronization unit for synchronizing the HD graphics signal output from the format conversion unit with the HDTV signal from the third switch is provided. First image signal inputted to the first input terminal NT
An NTSC / HDTV discriminator that discriminates whether the signal is an SC signal or an HDTV signal, switches the first, second, and third switches based on the discrimination result and switches whether or not format conversion is required by the format converter. And a synthesizing unit for synthesizing an output signal from the frame synchronization unit and an output signal from the second switch. The format conversion unit includes an A / D conversion unit for converting an input analog NTSC signal or HD graphics signal into a digital signal, and a memory for storing a video signal. A system converter for converting an NTSC signal into an HDTV signal format and outputting the same; and a switch interposed between the A / D converter and the system converter, wherein a digital signal from the A / D converter is When the signal is an NTSC signal, the NTSC signal is led to the format converter, and the digital signal from the A / D converter is
A switch unit for passing the HD graphics signal through the format conversion unit to the next frame synchronization unit when the signal is a D graphics signal, wherein the frame synchronization unit stores a video signal A digital NTSC signal converted to the HDTV signal format by the format converter, or A
A synchronizing unit for synchronizing the digital HD graphics signal subjected to only the / D conversion with reference to the signal selected by the third switch; and an HD graphics signal or H signal from the third switch.
DTV signal input, HD graphics signal or HD
A synchronizing signal generating unit that generates a synchronizing signal corresponding to a TV signal; a D / A converting unit that converts a digital NTSC signal or a digital HD graphics signal synchronized by the synchronizing unit into an analog signal and outputs the analog signal; The video synthesizing circuit according to claim 1, further comprising: