JP2818341B2 - S video output circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an S video output circuit for outputting an S video in a television receiver.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a conventional S video output circuit. In the figure, 1 is a luminance signal input terminal, 2
Is a color signal input terminal, 3 is a synchronizing signal separating circuit for extracting a synchronizing signal from the video luminance signal input to the luminance signal input terminal 1, and 4 is a CRT (not shown) based on the synchronizing signal output from the synchronizing signal separating circuit 3. 5) a synchronizing signal removing circuit for removing a synchronizing signal from a video luminance signal; 6 a video luminance signal from which the synchronizing signal has been removed in order to digitally process the video luminance signal; An 8-bit A / D converter for converting, a noise removing circuit 7 for performing a predetermined operation on the digitized video luminance signal between frames or between lines and removing noise, and a digital video luminance signal 8 from which noise has been removed A DA converter 9 for converting the signal into an analog signal, 9 a delay circuit for delaying the color signal input to the color signal input terminal, and 10 a video signal output from the DA converter 8 A video processing circuit for signal processing to display the color signal luminance signal delay circuit 9 is output to the CRT.

[0003] Reference numeral 11 denotes a luminance signal output terminal for supplying a video luminance signal to another video device having an S video input terminal such as a video tape recorder, and 12 denotes a color signal output terminal to another video device having an S video input terminal. A color signal output terminal 13 for supplying a signal; 13, an impedance conversion circuit for performing impedance conversion for outputting a video luminance signal input to the luminance signal input terminal 1 to the luminance signal output terminal 11;
Is an impedance conversion circuit that performs impedance conversion to output a color signal input to the color signal input terminal 2 to the color signal output terminal 12.

In general, an independent video luminance signal and a color signal are collectively referred to as an S video signal, and a luminance signal output terminal 11 for outputting an S video signal and a color signal output terminal 12 are collectively referred to as an S video output. It is called a terminal. The luminance signal input terminal 1 and the chrominance signal input terminal 2 are collectively called an S video input terminal.

Next, the operation will be described. A video luminance signal input to a luminance signal input terminal 1 from a video detection system of a television receiver or another video device is supplied to a synchronization signal separation circuit 3, a synchronization signal removal circuit 5, and an impedance conversion circuit 13. The synchronization signal separation circuit 3 extracts only the synchronization signal from the video luminance signal and supplies it to the deflection circuit 4. The deflection circuit 4 drives the deflection portion of the CRT using the synchronization signal.

As shown in FIG. 3, the synchronization signal removing circuit 5 first removes a synchronization signal portion from a video luminance signal.
Next, the signal is amplified by the amplitude of the removed synchronous signal portion, and the amplified signal is output to the AD converter 6. The A / D converter 6 converts the video luminance signal from which the synchronization signal has been removed into an 8-bit digital signal, that is, a digital signal of 256 gradations, and outputs the digital signal to the noise removal circuit 7.

The noise elimination circuit 7 performs noise elimination by subjecting the digitized video luminance signal to predetermined arithmetic processing between frames or between lines. The signal from which the noise has been removed is converted into an analog signal by the DA converter 8, and is converted into a video luminance signal without a synchronization signal from which the noise has been removed.

On the other hand, the color / luminance signal input to the color signal input terminal 2 is supplied to a delay circuit 9 and an impedance conversion circuit 1.
4 is supplied. The delay circuit 9 delays the chrominance signal in order to compensate for a time lag between the video luminance signal and the chrominance signal that have passed through the noise removal circuit 7. Then, the delayed color signal is supplied to the video processing circuit 10. The video processing circuit 1
An image is projected on a CRT by using the image luminance signal supplied from the DA converter 8 and a color signal whose timing is adjusted to the image luminance signal by the delay circuit 9.
At this time, the gradation of the projected image is 256.

The luminance video signal input to the luminance signal input terminal 1 is supplied to a luminance signal output terminal 11 via an impedance conversion circuit 13, and the color signal input to the chrominance signal input terminal 2 is subjected to impedance conversion. The signal is supplied to the color signal output terminal 12 via the circuit 14. Therefore, another video device connected to the S video output terminal can receive a video luminance signal and a color signal via the terminal.

Here, it is desirable to supply a video luminance signal from which noise has been removed to other video equipment connected to the S video output terminal. However, a signal without a synchronization signal is supplied.

[0011]

Since the conventional S-video output circuit is configured as described above, the S-video signal supplied from the S-video output terminal to another video device must not have noise removed. There was a problem that it was not obtained.
In order to solve this problem, the video luminance signal is passed to the noise removal circuit 7 without removing the synchronization signal, and
The video signal may be supplied to the video output terminal and the video processing circuit 10, but in this case, since the number of bits in the A / D converter 6 is limited, the gradation of the video displayed on the CRT is always the sync signal portion. , And 256 gradations are included, and the gradation of the original video portion is degraded by the synchronization signal portion.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the video luminance signal output from the S video output terminal has been subjected to noise removal, and other video equipment is not connected. In this case, it is an object to obtain an S video output circuit that does not degrade the gradation of a video displayed on a CRT.

[0013]

An S-video output circuit according to the present invention comprises: an S-video output terminal for outputting a video luminance signal and a color signal; a noise reduction process after digitizing the video luminance signal; A noise removing unit that outputs a signal to the S video output terminal, a detecting unit that detects that a plug is connected to the S video output terminal, and a video luminance signal that includes a synchronization signal in the noise removing unit when the detecting unit detects the connection of the plug. And a switching unit that supplies a video luminance signal from which the synchronization signal has been removed to the noise removal unit when the detection unit detects that the plug is not connected, and the output side of the noise removal unit is connected to the S video output terminal. Connected.

[0014]

The switching section in the present invention switches the video signal to be supplied to the noise removing section depending on whether or not a plug is connected to the S video output terminal. As a result, the noise elimination circuit can change the range to be digitized depending on whether the plug is connected or not.
It is possible to supply a video luminance signal from which noise has been removed including a synchronization signal to a video output terminal, and to supply a video whose gradation is not deteriorated to a CRT when a plug is not connected.

[0015]

[Embodiment 1] An embodiment of the present invention will be described below with reference to the drawings. In the figure, reference numeral 15 denotes a mechanical switch (detection unit) attached to the S video output terminal and closed when a plug is inserted into the S video output terminal. One of the contacts is grounded, and the other is connected to a power supply via a resistor 16. It is connected.
Reference numeral 17 designates one of the output of the synchronization signal removing circuit 5 and the video luminance signal input to the luminance signal input terminal 1 as A-D.
A changeover switch (switching unit) to be supplied to the converter 6. The changeover switch 17 selects the video luminance signal input to the luminance signal input terminal 1 when the mechanical switch 15 is closed, and selects the output of the synchronization signal removing circuit 5 when the mechanical switch 15 is opened.

In this case, the output of the DA converter 8 is supplied to the impedance conversion circuit 13 on the luminance signal output terminal 11 side, and the impedance conversion circuit 14 on the chrominance signal output terminal 12 side is supplied to the impedance conversion circuit 13. The output of delay circuit 9 is provided. Other configurations are the same as those shown in FIG. Note that the noise elimination unit includes an AD converter 6, a noise elimination circuit 7, and a DA converter 8.

Next, the operation will be described. When the plug is not connected to the S video output terminal, the mechanical switch 15 is open. Therefore, the changeover switch 17 is connected to the “H” side shown in FIG. 1, and the output of the synchronous signal removing circuit 5, that is, the video luminance signal without the synchronous signal is input to the AD converter 6. Therefore, as in the conventional case, the noise is removed from the video luminance signal excluding the synchronizing signal in the noise removing circuit 7, and the image of 256 gradations is displayed on the CRT via the video processing circuit 10.

At this time, the video signal supplied to the luminance signal output terminal 11 does not include a synchronization signal. However, since no plug is connected to the S image output terminal, the synchronization signal is not transmitted to other video equipment. No video luminance signal is supplied.

On the other hand, when a plug is connected to the S video output terminal, the mechanical switch 15 is closed. Therefore, the changeover switch 17 is connected to the “L” side shown in FIG.
The A / D converter 6 is supplied with a video luminance signal including a synchronization signal. Therefore, the A / D converter 6 digitizes the video luminance signal including the synchronization signal into an 8-bit digital signal. The noise removal circuit 7 performs a noise removal process on the digital signal, and the DA converter 8 returns the output of the noise removal circuit 7 to an analog signal. Therefore, D-
The output of the A converter 8 includes a synchronization signal part.

As a result, the luminance signal output circuit 11 is supplied with a video luminance signal which has been subjected to noise removal by the noise removal circuit 7 and includes a synchronization signal. Therefore, a video luminance signal with reduced noise is supplied to other video devices as compared with the conventional case. At this time, the video processing circuit 10 handles the video luminance signal after the A / D conversion including the synchronization signal, so that the video processing circuit 10 handles the video luminance signal after the A / D conversion excluding the synchronization signal. In comparison, the gradient is slightly deteriorated. However, as described above, when another video device is not connected, 256 gradations are secured.

[0021]

As described above, according to the present invention, when an S video output circuit supplies a signal passed through a noise removal circuit to an S video output terminal and a plug is connected to the S video output terminal. The input of the A / D converter in front of the noise elimination circuit is switched between when it is not performed, and when no other video equipment is connected, the same gradation as the conventional one is obtained. Images can be displayed on a CRT,
There is an effect that a video luminance signal from which noise has been removed can be supplied to another video device.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an S video output circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional S video output circuit.

FIG. 3 is a waveform diagram showing a video luminance signal waveform.

[Explanation of symbols]

 Reference Signs List 6 AD converter (noise removing unit) 7 Noise removing circuit (noise removing unit) 8 DA converter (noise removing unit) 11 Luminance signal output terminal (S video output terminal) 12 Color signal output terminal (S video Output terminal) 15 Mechanical switch (detection unit) 17 Changeover switch (switching unit)

Claims (1)

(57) [Claims] 1. An S-video output terminal comprising: an S-video output terminal for outputting a video luminance signal and a color signal; and a noise removing unit for performing noise removal processing after digitizing the video luminance signal and returning the analog signal to output. In the output circuit, a detection unit that detects that a plug is connected to the S video output terminal, and when the detection unit detects the connection of the plug, gives a video luminance signal including a synchronization signal to the noise removal unit. A switching unit that supplies a video luminance signal from which a synchronization signal has been removed to the noise removal unit when the detection unit detects that the plug is not connected, and an output side of the noise removal unit is connected to the S video output terminal. An S-video output circuit.