JPH08275024A - Video signal detection circuit - Google Patents

Abstract

PURPOSE: To improve the discrimination accuracy of presence of a video signal by using horizontal synchronizing signal information, a width of a horizontal synchronizing signal, number of horizontal lines and a color identification signal, thereby discriminating the presence of the video signal. CONSTITUTION: This video signal detection circuit is provided with a horizontal PLL circuit 12 outputting horizontal synchronizing signal information, a horizontal synchronizing signal width detection circuit 13 receiving the horizontal synchronizing signal and outputting the width information of the horizontal synchronizing signal, and a vertical counter 14 receiving a vertical synchronizing signal, recovering the vertical synchronizing signal, counting number of horizontal lines for each field, and outputting the information of the number of horizontal lines and also with a discrimination circuit 15 receiving the horizontal synchronizing signal information, the width information of the horizontal synchronizing signal, and the information of the number of horizontal lines, discriminating the presence of the video signal and outputting a video signal detection signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal detecting circuit in a digital color television receiver.

[0002]

2. Description of the Related Art In recent years, the trend toward digitalization in the signal processing of television has been increasing with the improvement in image quality and multifunction of television receivers, and whether the input signal is noise or a video signal. The video signal detection circuit, which detects the presence or absence of a video signal in order to detect the signal and perform optimum signal control according to the detected signal, is emphasized.

A conventional video signal detection circuit will be described below with reference to FIG. FIG. 3 shows the configuration of a conventional video signal detection circuit.

In FIG. 3, reference numeral 30 is an LPF which receives a digitized video signal and removes a chroma signal component and a noise component superimposed on the video signal. 31 is LP
It is a sync separation circuit that receives the output signal of F30 and separates the sync signal. A reference numeral 32 inputs the sync signal separated by the sync separation circuit 31 and a horizontal sync determination threshold value, reproduces and outputs the horizontal sync signal so that the phase of the sync signal matches the horizontal sync signal component, and is reproduced with the sync signal. When the phase difference from the horizontal synchronization signal is within the horizontal synchronization determination threshold value, for example, a signal “1” is output as horizontal synchronization information. When the phase difference is equal to or more than the horizontal synchronization determination threshold value, for example, the signal “0” is output. Is a horizontal PLL circuit that outputs 33 inputs the synchronization signal,
It is a vertical counter for reproducing the vertical synchronizing signal and counting the number of horizontal lines for each field. Reference numeral 34 is a discrimination circuit (for example, a microprocessor) for inputting horizontal synchronization information and discriminating the presence or absence of a video signal.

The operation of the video signal detection circuit configured as described above will be described below with reference to FIG.

First, as shown in FIG. 3, the digitized video signal is input to the LPF 30 to remove the chroma signal component and the noise component superimposed on the video signal.
The output signal of the LPF 30 is input to the sync separation circuit 31 and the sync signal is separated from the video signal.

Next, the separated sync signal is input to the horizontal PLL circuit 32 to reproduce the horizontal sync signal, and the phase error between the reproduced horizontal sync signal and the input sync signal is used as a horizontal sync determination threshold value. When the phase error is compared and within the threshold for horizontal synchronization determination, the signal "1" is output as horizontal synchronization information.
Is output, and a signal “0” is output when the phase error is equal to or more than the horizontal synchronization determination threshold value.

The synchronizing signal is also input to the vertical counter 33 to reproduce the vertical synchronizing signal and count the number of horizontal lines for each field. The horizontal synchronization information is input to the microprocessor 34, and when the horizontal synchronization information is the signal "1", it is determined that the video signal is present, and when the signal is "0", it is determined that the video signal is not present, and the tuner channel search control is performed. Alternatively, the optimum control of the synchronization characteristic is performed according to the presence / absence of the video signal for horizontal synchronization of the horizontal PLL.

[0009]

However, the above configuration has a problem that the horizontal synchronization information becomes unstable due to noise or a signal whose image quality is deteriorated such as VTR.

The present invention has been made in consideration of the above problems, and the presence / absence of a video signal is determined by using the horizontal synchronization information, the horizontal synchronization signal width, the number of horizontal lines, and the color identification signal. Therefore, it is an object of the present invention to provide a video signal detection circuit in consideration of improving the accuracy of determining the presence / absence of a video signal.

[0011]

In order to solve the above problems, a video signal detection circuit of the present invention inputs a digitized video signal and removes a chroma signal component and a noise component superimposed on the video signal. The LPF and the output signal of the LPF are input, the sync separation circuit that separates the sync signal, the sync signal separated by the sync separation circuit, and the horizontal synchronization determination threshold are input, and the phase of the sync signal to the horizontal sync signal component is input. When the phase difference between the sync signal and the reproduced horizontal sync signal is within the threshold for horizontal sync determination, 1 is output as the horizontal sync information and the phase difference is horizontal. A synchronous reproduction circuit composed of a horizontal PLL circuit that outputs 0 when it is greater than or equal to a synchronization determination threshold value, and a horizontal synchronization signal width detection circuit that inputs a synchronization signal and outputs width information of the horizontal synchronization signal, Flat type synchronization information and horizontal synchronization signal width, and a discrimination circuit for outputting a video signal detection signal to determine the presence or absence of the video signal from the horizontal synchronization information and horizontal synchronization signal width.

When the horizontal synchronizing information is 1 and the horizontal synchronizing signal width falls within a predetermined range, the discriminating circuit discriminates that the video signal is present, and otherwise determines that there is no video signal, and determines the video signal detection signal. Output it.

Further, the LPF, the sync separation circuit, the horizontal PLL circuit, a vertical counter for inputting the sync signal, reproducing the vertical sync signal, and counting the number of horizontal lines in each field, are provided. The number of horizontal lines may be input to the determination circuit, the presence or absence of a video signal may be determined from the horizontal synchronization information and the number of horizontal lines, and a video signal detection signal may be output.

For example, in the above discrimination circuit, when the horizontal synchronizing information and the number of horizontal lines are input, and when the horizontal synchronizing information is 1 and the number of horizontal lines is within a predetermined range, a video signal is present, and other than that. It is preferable to determine that there is no case and output the video signal detection signal.

The LPF, the sync separation circuit, the horizontal PLL circuit, the horizontal sync signal width detection circuit, and the vertical counter are provided to determine the horizontal sync information, the horizontal sync signal width, and the number of horizontal lines. Alternatively, the video signal detection signal may be input to the circuit, and the video signal detection signal may be output by determining the presence or absence of the video signal from the horizontal synchronization information, the horizontal synchronization signal width, and the number of horizontal lines.

For example, when the horizontal synchronizing information, the horizontal synchronizing signal width, and the number of horizontal lines are input to the discriminating circuit and a signal such as a VTR signal in which the number of horizontal lines is not constant is selected as a video signal, the horizontal synchronizing information is the signal " 1 ”and when the horizontal synchronizing signal width falls within a predetermined range, the video signal is determined to be“ present ”, otherwise the video signal is determined to be“ absent ”, and the RF signal is selected as the video signal. In this case, when the horizontal synchronization information is the signal “1” and the number of horizontal lines is within a predetermined range, the video signal is determined to be “present”, and otherwise, the video signal is determined to be “absent” and the video signal is determined to be “not present”. It is more effective to output the signal detection signal.

Further, a YC separation circuit for inputting a digitized video signal and separating the video signal into a luminance signal and a chroma signal, and a chroma signal output from the YC separation circuit are inputted to reproduce a color subcarrier and succeed in reproduction. In this case, if the color identification signal, which is the information indicating the presence / absence of a color signal, is changed to, for example, the signal “0”, and the reproduction of the color subcarrier is failed, for example, the color PLL circuit that outputs the signal “1”, the chroma signal and the color A video circuit composed of a color demodulation circuit that inputs a carrier wave and performs color demodulation to reproduce a U signal and a V signal;
A PF, the sync separation circuit, the horizontal PLL circuit, the horizontal sync signal width detection circuit, and the vertical counter are provided, and the discrimination circuit includes the horizontal sync information, the horizontal sync signal width, the number of horizontal lines, and the color identification signal. Alternatively, the presence or absence of a video signal may be determined from the horizontal synchronization information, the horizontal synchronization signal width, the number of horizontal lines, and the color identification signal, and the video signal detection signal may be output.

For example, in the above discrimination circuit, when the horizontal synchronizing information, the horizontal synchronizing signal width, the number of horizontal lines and the color identification signal are input and a signal such as a VTR signal whose number of horizontal lines is not constant is selected as the video signal, the horizontal When the sync information is 1 and the horizontal sync signal width is within a predetermined range, or when the horizontal sync information is 1 and the horizontal sync signal width is outside the predetermined range and the color identification signal is 0. , If there is a video signal, it is determined that there is no other case, and if the RF signal is selected as the video signal,
When the horizontal synchronization information is 1 and the number of horizontal lines falls within a predetermined range, it may be determined that the video signal is present and otherwise the video signal detection signal may be output.

Further, it is preferable to use a microprocessor for the discrimination circuit.

[0020]

According to the present invention, with the above configuration, the presence / absence of a video signal is determined by using the horizontal synchronization information, the horizontal synchronization signal width, the number of horizontal lines, and the color identification signal to determine the presence / absence of a video signal. Is possible.

[0021]

【Example】

(Embodiment 1) A video signal detection circuit according to a first embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows the configuration of a video signal detection circuit according to the first embodiment of the present invention. In FIG. 1, reference numeral 10 denotes an LPF which inputs a digitized video signal and removes a chroma signal component and a noise component superimposed on the video signal. Reference numeral 11 is a sync separation circuit that receives the output signal of the LPF 10 and separates the sync signal. Reference numeral 12 inputs the sync signal separated by the sync separation circuit 11 and a horizontal sync determination threshold value, reproduces and outputs the horizontal sync signal so that the phase of the sync signal matches the horizontal sync signal component, and reproduces the sync signal. When the phase difference from the generated horizontal synchronization signal is within the horizontal synchronization determination threshold value, for example, a signal “1” is output as horizontal synchronization information. When the phase difference is equal to or more than the horizontal synchronization determination threshold value, for example, the signal “0” is output. Is a horizontal PLL circuit that outputs ".

Reference numeral 13 is a horizontal sync signal width detection circuit which receives the sync signal output from the sync separation circuit 11 and outputs the width information of the horizontal sync signal. Reference numeral 14 is a vertical counter which receives the sync signal output from the sync separation circuit 11 and reproduces the vertical sync signal and counts the number of horizontal lines for each field. Reference numeral 15 is a microprocessor for inputting horizontal synchronization information, horizontal synchronization signal width, and number of horizontal lines to determine the presence or absence of a video signal.

The operation of the video signal detection circuit according to the first embodiment of the circuit configured as described above will be described below with reference to FIG. First, as shown in FIG. 1, the digitized video signal is input to the LPF 10 to remove a chroma signal component and a noise component superimposed on the video signal. The output signal of the LPF 10 is input to the sync separation circuit 11 and the sync signal is separated from the video signal.

Next, the separated sync signal is input to the horizontal PLL circuit 12 to reproduce the horizontal sync signal. Then, the phase error between the reproduced horizontal synchronization signal and the input synchronization signal is compared with the separately input threshold value for horizontal synchronization determination, and when the phase error is within the threshold value for horizontal synchronization determination, the horizontal synchronization information For example, the signal “1” is output,
If the phase error is larger than the horizontal synchronization determination threshold value, for example, a signal “0” is output. Signal "0", "1"
Is not limited to this signal, but may be any signal as long as it can be discriminated whether it is larger or smaller than the horizontal synchronization determination threshold value.

The sync signal output from the sync separation circuit 11 is input to the horizontal sync signal width detection circuit 13 and outputs the width information of the horizontal sync signal.

The synchronization signal is also input to the vertical counter 14 to reproduce the vertical synchronization signal and count the number of horizontal lines for each field.

The horizontal synchronization information output from the horizontal PLL circuit 12, the signal indicating the horizontal synchronization signal width output from the horizontal synchronization signal width detection circuit 13, and the signal indicating the number of horizontal lines output from the vertical counter 14 are When input to the microprocessor 15 and a standard signal such as a television broadcast is input as a video signal, the horizontal synchronization information is "1" and the number of horizontal lines is within a range of about three lines before and after the number of lines for the standard signal. If it enters, the video signal is determined to be "present", and otherwise, the video signal is determined to be "absent".

When a signal such as a VTR signal in which the number of horizontal lines is not constant is selected as the video signal, the horizontal synchronization information is "1" and the width of the horizontal synchronization signal is several 10 before and after the width of the standard signal. When it is within the range of%, it is determined that the video signal is “present”, and otherwise, the video signal is determined as “absent” and the video signal detection signal is output.

As described above, according to the video signal detection circuit shown in the present embodiment, when a noise signal is input as a video signal, the number of horizontal lines output from the vertical counter is generally the number of horizontal lines shown in the standard signal. Since there is a tendency to largely deviate, the video signal is "present" when the horizontal synchronization information and the number of horizontal lines simultaneously satisfy the synchronization condition, rather than determining the presence or absence of the video signal only by the number of horizontal lines.
Therefore, the accuracy of video signal detection can be improved.

When the noise signal is input to the video signal, the horizontal sync signal width detection circuit 13 tends to have a width much smaller than the width of the standard signal. Even if the horizontal PLL circuit 12 is erroneously output, the video signal detection accuracy is determined by determining that the video signal is “present” only when the horizontal synchronization information and this horizontal synchronization signal width satisfy the conditions for synchronization. Can be improved.

The detection method in which the horizontal synchronizing signal width is added as a condition is particularly effective when video signal detection is performed on a signal source such as a VTR in which the number of horizontal lines is not stable.

(Second Embodiment) A video signal detection circuit according to a second embodiment of the present invention will be described below with reference to FIG.

FIG. 2 shows the configuration of a video signal detection circuit according to the second embodiment of the present invention. In FIG. 2, reference numeral 20 is a YC separation circuit which inputs a digitized video signal and separates the video signal into a luminance signal and a chroma signal. A reference numeral 22 inputs a chroma signal, reproduces a color subcarrier, and outputs a color identification signal indicating the presence or absence of a chroma signal to, for example, "0" when the reproduction is successful, and outputs "1" when the reproduction fails. It is a color PLL circuit.
Reference numeral 21 is a color demodulation circuit for inputting a chroma signal and a color subcarrier and performing color demodulation to reproduce a U signal and a V signal. Further, the color identification signal output from the color PLL circuit is input to the microprocessor 15.

The structure shown in FIG. 1 is almost the same as the structure shown in the first embodiment, and the operation thereof is the same, so that the description thereof is omitted here.

An operation example of the video signal detection circuit configured as described above will be described with reference to FIG.

The digitized video signal is the LPF 10
To the chroma signal component and the noise component superimposed on the video signal are removed. The output signal of the LPF 10 is input to the sync separation circuit 11 and the sync signal is separated from the video signal.

Next, the separated sync signal is input to the horizontal PLL circuit 12 to reproduce the horizontal sync signal, and the phase error between the reproduced horizontal sync signal and the input sync signal is used as a horizontal sync determination threshold value. When the phase error is compared and is within the horizontal synchronization determination threshold value, for example, a signal “1” is output as horizontal synchronization information, and when the phase error is equal to or greater than the horizontal synchronization determination threshold value, for example, a signal 0 is output.

The sync signal is also the horizontal sync signal width detection circuit 1
3 and outputs the width information of the horizontal synchronizing signal.

The sync signal is also input to the vertical counter 14 to reproduce the vertical sync signal and count the number of horizontal lines for each field.

The horizontal synchronizing information, the horizontal synchronizing signal width, the number of horizontal lines, and the color identification signal output from the color PLL circuit 22 are input to the microprocessor 15, and standard signals for television broadcasting are input as video signals. In this case, if the horizontal synchronization information is the signal "1" and the number of horizontal lines is within the range of about 3 lines before and after the number of lines for the standard signal, the video signal is "present".
If not, it is determined that the video signal is “absent”.

When a signal such as a VTR signal in which the number of horizontal lines is not constant is selected as the video signal, the horizontal synchronizing information is the signal "1" and the width of the horizontal synchronizing signal is a number before and after the width of the standard signal. When it is within the range of 10%, or when the horizontal synchronization information is the signal “1” and the horizontal synchronization signal width is outside the range of several 10% before and after the width of the standard signal and the color identification signal is “0”. If there is, the video signal is determined to be “present”, and if not, the video signal is determined to be “absent”.

The effects of the video signal detection circuit of this embodiment will be described below. Generally, when the noise signal is input as a video signal, the number of horizontal lines output from the vertical counter tends to deviate greatly from the number of horizontal lines shown in the standard signal. However, if the video signal is determined to be “present” when the horizontal synchronization information and the number of horizontal lines simultaneously satisfy the synchronization condition as in the present embodiment, the accuracy of video signal detection can be improved. it can.

In general, when the noise signal is input to the video signal, the horizontal sync signal width of the horizontal sync signal width detection circuit tends to be much smaller than the width shown for the standard signal. Even if the information is erroneously output, the video signal detection accuracy can be improved by determining that the video signal is present only when the horizontal synchronization information and the horizontal synchronization signal width or the synchronization are satisfied.

Since the color subcarrier can be reproduced with high accuracy even when a signal in which a video signal and a sync signal are deteriorated by a VTR or the like is input as a video signal, this color identification signal succeeds in reproducing the color subcarrier. In this case, the color identification signal output from the color PLL circuit 22 is output as information indicating the presence / absence of a video signal, so that the video signal is determined to be “present”, and horizontal synchronization information or horizontal synchronization is performed by a VTR or the like. Even if the detection of the signal width is erroneously determined to be “absent”, the video signal can be detected correctly.

As described above, according to the video signal detecting circuit of the present embodiment, the presence or absence of the video signal is determined by using the horizontal synchronizing information, the horizontal synchronizing signal width, the number of horizontal lines and the color identification signal. Therefore, it is possible to improve the accuracy of determining the presence / absence of a video signal.

[0047]

As described above, according to the present invention, the presence / absence of a video signal is determined by using the horizontal synchronization information, the horizontal synchronization signal width, the number of horizontal lines, and the color identification signal. The accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a video signal detection circuit according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a video circuit according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a conventional video signal detection circuit.

[Explanation of symbols]

 10, 30 LPF 11, 31 Sync separation circuit 12, 32 Horizontal PLL 13 Horizontal sync signal width detection circuit 14, 33 Vertical counter 15, 34 Microprocessor 20 YC separation circuit 21 Color demodulation circuit 22 Color PLL circuit

Claims (5)

[Claims] 1. An LPF for removing a noise component superimposed on an input digitized video signal, and the LPF.
Of the sync signal and the threshold value for horizontal sync determination separated by the sync separation circuit are input, and the phase of the sync signal matches the horizontal sync signal component. The horizontal synchronization information when the horizontal synchronization signal is reproduced and the phase difference between the synchronization signal and the reproduced horizontal synchronization signal is within the horizontal synchronization determination threshold value and above the horizontal synchronization determination threshold value. A horizontal PLL circuit that outputs different signals, a horizontal synchronization signal width detection circuit that inputs the synchronization signal and outputs width information of the horizontal synchronization signal, and the horizontal synchronization information and width information of the horizontal synchronization signal that are input, A video signal detection circuit including a determination circuit that determines the presence or absence of a video signal and outputs a video signal detection signal. 2. An LPF for removing a noise component superimposed on an input digitized video signal, and the LPF.
Inputting the output signal of the sync signal and separating the sync signal, the period signal separated by the sync separation circuit and the threshold for horizontal sync determination are input, and the sync signal is in phase with the horizontal sync signal component. The horizontal synchronization information when the horizontal synchronization signal is reproduced and the phase difference between the synchronization signal and the reproduced horizontal synchronization signal is within the horizontal synchronization determination threshold value and above the horizontal synchronization determination threshold value. A horizontal PLL circuit that outputs different signals, a vertical counter that inputs the synchronization signal, reproduces the vertical synchronization signal, and counts the number of horizontal lines in each field, and inputs the horizontal synchronization information and the information of the number of horizontal lines And a video signal detection circuit configured to determine the presence or absence of a video signal and output a video signal detection signal. 3. An LPF for removing a noise component superimposed on an input digitized video signal, and the LPF.
, A horizontal sync signal width detecting circuit for inputting the sync signal and outputting width information of the horizontal sync signal, and a vertical sync signal for inputting the sync signal. And a vertical counter that counts the number of horizontal lines for each field and outputs the information of the number of horizontal lines, and the width information of the horizontal synchronizing signal and the information of the number of horizontal lines are input to determine the presence or absence of a video signal. A video signal detection circuit including a determination circuit that outputs a video signal detection signal. 4. An LPF for removing a noise component superimposed on an input digitized video signal, and the LPF.
Of the sync signal and the threshold value for horizontal sync determination separated by the sync separation circuit are input, and the phase of the sync signal matches the horizontal sync signal component. The horizontal synchronization information when the horizontal synchronization signal is reproduced and the phase difference between the synchronization signal and the reproduced horizontal synchronization signal is within the horizontal synchronization determination threshold value and above the horizontal synchronization determination threshold value. , A horizontal PLL circuit that outputs different signals, a horizontal sync signal width detection circuit that inputs the sync signal and outputs width information of the horizontal sync signal, and a horizontal sync signal width detection circuit that inputs the sync signal and reproduces the vertical sync signal and for each field. A vertical counter that counts the number of horizontal lines and outputs the information of the number of horizontal lines, the horizontal synchronization information, the width information of the horizontal synchronization signal, and the information of the number of horizontal lines are input, and Video signal detecting circuit configured to determine the presence or absence of O signal from a determination circuit for outputting a video signal detection signal. 5. A YC separation circuit that separates a video signal into a luminance signal and a chroma signal, and a signal that differs depending on whether the chroma sub-signal is input and the color subcarrier is reproduced and the reproduction is successful or not. A color PLL circuit for outputting a color identification signal) and a color identification signal output from the color PLL circuit are input to a discrimination circuit. The video signal detection circuit according to claim 1.