JPH04261780A - Television signal converter - Google Patents

Abstract

PURPOSE:To provide a television signal converter, formed to convert a high- quality television signal (MUSE signal) into a current standard television signal (NTSC signal) so as to be regenerated in an existing television receiver, with the ability to prevent noise arising on a monitor image plane due to blanking image signal output for a fixed time or switching the image signal output when horizontal synchronization is out of detection at the time of the MUSE signal being switched into silence or into a signal other than the MUSE signal. CONSTITUTION:This television signal converter is provided with an A/D converter 1, a signal processing circuit 2, an analog switch 3, an HD detecting means 4 for detecting HD (horizontal synchronizing signal) from timing pulses outputted from the signal processing circuit 2 during the HD period, and a blanking circuit 5 so as to prevent the generation of noise arising on a monitor image plane due to blanking image output at the time of being out of HD detection.

Description

Detailed Description of the Invention [0001] [Industrial Application Field] The present invention is directed to a high-definition television signal (MUSE signal).
Sub Nyquist Sampling)
NT signal, which is the current standard television signal.
SC (National Television)
System Committee) signal,
The present invention relates to a television signal converter having a function of blanking a video signal output for a certain period of time or switching the video signal output when horizontal synchronization of a high-definition television signal (MUSE signal) becomes undetectable. [Prior Art] In recent years, as a high-definition television transmission system, the current standard television signal (NTSC signal), which is a conventional television signal, such as the MUSE signal, which samples one image in 4 fields and transmits it. Television signals of different transmission formats have been developed and used. Along with this, high-definition television signals (MUSE)
It has become necessary to convert the current standard television signal (NTSC signal) into a current standard television signal (NTSC signal) and reproduce it on a conventional television receiver. [0003] A conventional television signal converter will be explained below. FIG. 6 shows a schematic block diagram of a conventional television signal conversion device. In Figure 6,
1 is an external BS (Broadcasting Sat
A for converting a high-definition television signal (MUSE signal), which is an analog signal input from a tuner (not shown) through terminal A, into a digital signal.
/D converter, 2 is a signal processing circuit for converting the output of the A/D converter 1 into a current standard television signal (NTSC signal), 3 is a current standard television signal (NTSC signal) output from the signal processing circuit 2 C is an analog switch for switching between the current standard television signal (NTSC signal) input from an external BS tuner (not shown) through terminal B, and C is for switching the output from analog switch 3 to an external monitor (Fig. (not shown). [0004] The operation of the television signal converter configured as described above will be explained below. In FIG. 6, a high-definition television signal (MUSE signal) input from an external BS tuner is input from input terminal A, is converted into a digital signal by A/D converter 1, and is then converted to a digital signal by signal processing circuit 2 according to the current standard. The signal is converted into a television signal (NTSC signal) and input to the analog switch 3. On the other hand, the current standard television signal (NTSC signal) from the outside inputted from the input terminal B is also inputted to the analog switch 3, and when the high-definition television signal (MUSE signal) is detected in the signal processing circuit 2, the signal processing The current standard television signal (NTSC signal) converted by circuit 2 was selected, switched by the output control signal, and output to the external monitor through terminal C, and the high-definition television signal (MUSE signal) was not detected. At times, a current standard television signal (NTSC signal) from the outside inputted from input terminal B is outputted to an external monitor through terminal C. [0005] However, in the conventional television signal converter described above, detection of a high-definition television signal (MUSE signal) is performed for each frame (vertical synchronization period). Television signal (M
Because it is necessary to protect synchronization in response to the deterioration of the C/N ratio of the USE signal), the output timing of the output control signal was delayed, and the high-definition television signal (MUSE signal) was switched, resulting in no signal. There is a problem in that, at times, noise appears in the video signal output for several fields, resulting in unsightly noise being displayed on the monitor screen. [0006] The present invention solves the above-mentioned conventional problems, and uses a simple configuration to provide high-definition television signals (M
USE signal) and then input the current standard television signal (
NTSC signal) and high-definition television signal (M
An object of the present invention is to provide a television signal converter having a function of blanking the video signal output for a certain period of time or switching the video signal output when the horizontal synchronization of the USE signal becomes undetectable. It is. Means for Solving the Problems In order to achieve the above object, the television signal conversion device of the present invention uses an A/D that inputs a high-definition television signal (MUSE signal) and converts it into a digital signal. A signal processing circuit that converts the output of the converter and A/D converter into a current standard television signal (NTSC signal), and a high-definition television signal (MUSE signal) that converts the current standard television signal input from the outside and the above signal processing circuit. ), a blanking circuit for blanking the video signal for a certain period of time, and a means for detecting the HD (horizontal synchronization signal).
(Horizontal synchronization signal) detection circuit is provided. [Operation] Therefore, according to the television signal conversion device of the present invention, high-definition television signals (MUSE signals)
When the signal changes and there is no signal, or when the signal becomes a signal other than a high-definition television signal (MUSE signal), horizontal synchronization cannot be detected, and the video signal output must be blanked for a certain period of time, or the video signal output must be blanked. By changing the settings, it becomes possible to prevent noise from appearing on the monitor screen. Embodiment (Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, parts common to those in the conventional example shown in FIG. 6 are designated by the same reference numerals, and detailed description thereof will be omitted. 4 is an HD detection means for detecting HD (horizontal synchronization signal) from a signal outputted by a timing pulse outputted during the HD period from the signal processing circuit 2; 5 is a means for blocking the video signal output of the analog switch 3 for a certain period of time; This is a blanking circuit for ranking. The operation of the television signal converter configured as described above will be explained using FIG. 2. Figure 2 shows the HD signal (horizontal synchronization signal) in the high-definition television signal (MUSE signal) and the HD signal from the signal processing circuit 2.
FIG. 2A is a waveform diagram showing the timing of timing pulses output during a period, and FIG. Figure 2(b) shows the relationship between the HD signal waveform and the timing pulse from the video signal processing circuit 2 when no high-definition television signal (MUSE signal) is input from terminal A. It shows the relationship between In this way, as shown in FIG. 2(b), a high-definition television signal (MU
When the SE signal) is not input, a control signal is output from the HD detection means 4 to the blanking circuit 5, and the video signal output is blanked for a certain period of time, suppressing the video signal output for a certain period of time, which is unnecessary. This means that noise will not appear on the monitor screen. (Embodiment 2) A second embodiment of the present invention will be described below with reference to the drawings. In FIG. 3, the same parts as those in the conventional example shown in FIG. 6 is A
A D flip-flop inputs the most significant bit (MSB) of the output of the /D converter 1 and latches data with a timing pulse output from the signal processing circuit 2 during the HD period, and 7 is the D flip-flop described above. a D flip-flop for latching the output data of 6 with a timing pulse output from the signal processing circuit 2 during the HD period;
8 is a D flip-flop for latching the output data of the D flip-flop 7 with a timing pulse output from the signal processing circuit 2 during the HD period; 9 is an OR of the outputs of the D flip-flop 6 and D flip-flop 7; 10 is an OR gate that takes the OR of D flip-flop 7 and D flip-flop 8, 11 is the OR gate that takes the above O
The output of an AND gate 11, which is an AND gate that ANDs an R gate 9 and an OR gate 10, is input to a blanking circuit 4. Next, the operation of the second embodiment will be explained. As shown in Figure 2(a), the HD waveform of the high-definition television signal (MUSE signal) is inverted line by line, and its level is 192/256 at the maximum and 192/256 at the minimum when converted in 8-bit units. 64/256, A/
The most significant bit (MSB) of D converter 1 is inverted line by line. Therefore, a high definition television signal (M
USE signal) is input from terminal A, the above D
The outputs of flip-flop 6, D flip-flop 7, and D flip-flop 8 are Hi (hereinafter abbreviated as H).
and Low (hereinafter abbreviated as L) and H or L, H and L. At this time, the output of AND gate 11 is OR gate 9, 1
The logic circuit consisting of 0 becomes H, and the outputs of D flip-flops 6, 7, and 8 become L, L, H or H, H.
, L, the output of the AND gate 11 becomes H. However, when the outputs of the D flip-flops 6, 7, and 8 all match H, H, H or L, L, L, it means that the HD of the high-definition television signal (MUSE signal) cannot be detected. The output of AND gate 11 is L
becomes. Therefore, when the output of the AND gate 11 is L, that is, when HD (horizontal synchronization signal) cannot be detected, the output of the AND gate 11 becomes L, is input to the blanking circuit 5, and the video signal output is kept constant. Time blanking is applied and the video signal output is suppressed for a certain period of time, making it possible to control so that unnecessary noise does not appear on the monitor screen. 001
5] (Embodiment 3) A third embodiment of the present invention will be described below with reference to the drawings. To simplify the explanation, a case will be described in which the HD signal detection period is performed over two lines. Further, in FIG. 4, parts common to the second embodiment shown in FIG. 2 and the conventional example shown in FIG. In this embodiment, the D flip-flop 6 and the D flip-flop 8 are arranged in parallel, and data from the A/D converter 1 is input to both at the same timing. 12 is a D flip-flop for latching the output data of the D flip-flop 8; 13 is for inverting the timing pulse output from the signal processing circuit 2 during the HD period and latching the D flip-flops 8 and 12; , 14 is an OR gate that ORs the outputs of D flip-flop 7 and D flip-flop 12, and 15 is an OR gate that ORs the outputs of D flip-flop 8 and D flip-flop 1.
OR gate that takes OR of 2, 16 is OR gate 9, 14
, is an AND gate that takes AND of 15, and this AND
The output of the gate 16 is input to the blanking circuit 5. The operation of the third embodiment of the television signal converter configured as described above will be described below. As shown in Figure 2(a), the HD waveform of the high-definition television signal (MUSE signal) is inverted line by line, and its level is 192/256 at the maximum and 192/256 at the minimum when converted in 8-bit units. It becomes 64/256,
The most significant bit (MSB) of the A/D converter 1 is inverted line by line, and the rising and falling edges of the timing pulse from the signal processing circuit 2 are inverted within one line. Therefore, high-definition television signal (MUSE signal)
is input from terminal A, the above-mentioned D flip-flop 6, D flip-flop 7, and D flip-flop 8
and the outputs of the D flip-flop 12 are H, L,
The signal becomes H, L or L, H, L, H, and the output of the AND gate 16 at this time becomes H. In addition, the above-mentioned D flip-flop 6, D flip-flop 7, and D flip-flop 8
and the outputs of the D flip-flop 12 are H, H,
The AND gate 16 is operated in the same manner as in the second embodiment except when all data such as H, H, L, L, L, L, etc. match.
The output becomes H. However, D flip-flop 6 and D
The respective outputs of flip-flop 7, D flip-flop 8 and D flip-flop 12 are H, H, H, H and L.
, L, L, L, etc., it means that HD of the high-definition television signal (MUSE signal) cannot be detected, and the output of the AND gate 16 becomes L, which is different from the second embodiment. Similarly, the output of the AND gate 16 is input to the blanking circuit 5, and the video signal output is blanked for a certain period of time, suppressing the video signal output for a certain period of time, so that unnecessary noise does not appear on the monitor screen. be able to control. (Embodiment 4) The fourth embodiment of the present invention will be explained below with reference to the drawings. To simplify the explanation, a case will be described in which the HD signal detection period is performed over two lines. Further, in FIG. 5, parts common to those in the third embodiment shown in FIG. 4 are given the same reference numerals, and detailed explanations will be omitted. In this embodiment, the output of the AND gate 16 is input to the analog switch 3, and the output signal of the analog switch 3 is controlled. The operation of the third embodiment of the television signal converter configured as described above will be explained below. Similarly to the third embodiment, the respective outputs of the D flip-flop 6, the D flip-flop 7, the D flip-flop 8, and the D flip-flop 12 are H, H, H.
, H, L, L, L, L, etc., when all data match, the HD of the high-definition television signal (MUSE signal)
This means that HD has not been detected, and the output of the AND gate 16 becomes L; otherwise, it means that HD has been detected, and the output of the AND gate 16 becomes H. When the output of this AND gate 16 is H, the current standard television signal (N
TSC signal) is selected, and the output of the AND gate 16 is L.
Then, when a high-definition television signal (MUSE signal) is not detected, the output signal of the analog switch 3 is controlled so that the current external standard television signal (NTSC signal) inputted from input terminal B is selected. Therefore, high-definition television signal (MUSE signal)
By switching the video signal output when horizontal synchronization becomes undetectable, noise appearing on the monitor screen can be prevented. In the second, third and fourth embodiments described above, the HD detection period is configured with 2 lines and 3 lines, respectively, and the audio is detected only when the data of all D flip-flops match. Although the configuration suppresses the signal, it is possible to increase the HD detection period and suppress the audio signal when the outputs of some of the D flip-flops become H or L continuously. The same effect can be obtained even if the logic circuit is configured so that it can be suppressed. Furthermore, it goes without saying that similar effects can be obtained even if the logic circuit of the HD detection means in the fourth embodiment is configured as in the second embodiment. As described above, the present invention adds an HD (horizontal synchronization signal) detection circuit and a blanking circuit as means for detecting an HD (horizontal synchronization signal), thereby making it possible to detect high-definition television signals. (MUSE signal) is switched and there is no signal, or when the signal becomes a signal other than the high-definition television signal (MUSE signal), horizontal synchronization cannot be detected and the video signal output is blanked for a certain period of time, or By switching the video signal output, it is possible to realize a television signal conversion device that can prevent noise appearing on a monitor screen.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of a television signal conversion device in a first embodiment.

[Figure 2] Waveform diagram showing the timing of the HD signal (horizontal synchronization signal) and the timing pulse from the signal processing circuit 2

[Figure 3
] A schematic block diagram showing the configuration of a television signal converter according to a second embodiment of the present invention.

[Fig. 4] Third aspect of the present invention
A schematic block diagram of a television signal conversion device showing the configuration of a television signal conversion device in an embodiment of

FIG. 5 is a schematic block diagram of a television signal conversion device showing the configuration of a television signal conversion device in a fourth embodiment of the present invention.

[Fig. 6] Schematic block diagram of a conventional television signal conversion device

[Explanation of symbols]

1 A/D converter 2 Signal processing circuit 3 Analog switch 4 HD detection means 5 Blanking circuit 6 D flip-flop 7 D flip-flop 8 D flip-flop 9 OR gate 10 OR gate 11 AND gate 12 D flip-flop 13 Inverter 14 OR gate 15 OR gate 16 AND gate A Input terminal for high-definition television signal (MUSE signal) B Input terminal for current standard television signal (NTSC signal) C Output terminal for external monitor

Claims (4)

[Claims] Claim 1: An A/D converter that inputs a high-definition television signal (MUSE signal) and converts it into a digital signal, and a signal that converts the output of the A/D converter into a current standard television signal (NTSC signal). a processing circuit;
An analog switch for switching between the current standard television signal input from the outside and the current standard television signal converted from the high-definition television signal (MUSE signal) by the signal processing circuit, and for blanking the video signal for a certain period of time. Equipped with a blanking circuit and means for detecting HD (horizontal synchronization signal), this function blanks the video signal output for a certain period of time when horizontal synchronization of the high-definition television signal (MUSE signal) cannot be detected. A television signal converter equipped with Claim 2: HD (horizontal synchronization signal) detection means that detects the most significant bit (MSB) of the output from the A/D converter.
) is input to a plurality of D flip-flops connected in series, latched by a timing pulse outputted during the HD period from a signal processing circuit, and the plurality of outputs of the D flip-flops are input to a plurality of OR gates, respectively. By inputting the output to multiple AND gates, the above A/
Equipped with an HD detection circuit that detects horizontal synchronization of a high-definition television signal (MUSE signal) by detecting coincidence or mismatch of the outputs of the D converter, the blanking circuit is controlled by the output of the HD detection circuit, and the high-definition 2. The television signal converter according to claim 1, wherein blanking is applied to the video signal output for a certain period of time when horizontal synchronization of the quality television signal (MUSE signal) becomes undetectable. [Claim 3] D flip-flop, OR gate, and A
By inserting an inverter in addition to the ND gate, H
3. The television signal conversion device according to claim 1, wherein the D (horizontal synchronization signal) detection period is shortened. 4. Claim 1, wherein when the horizontal synchronization of the high-definition television signal (MUSE signal) becomes undetectable, the analog switch is controlled by the output of the HD detection circuit to change the video signal output. Claim 2 or Claim 3
The television signal converter described above.