JPH077720A - Picture format conversion circuit - Google Patents

Abstract

PURPOSE:To easily build up the picture format conversion circuit at a low cost by using a sampling signal having a frequency in response to a frequency of a horizontal picture element number of an analog NTSC picture signal so as to apply A/D-conversion to the analog NTSC picture signal into a common intermediate format signal. CONSTITUTION:An NTSC decoder 201 converts an analog NTSC picture signal S1 into a luminance signal SY and color difference signals SCr, SCb by using a clock signal having a predetermined frequency from a clock signal generating circuit 208. Then the signal SY is fed to an A/D converter circuit 204 through BPFs 202, 203 and a switch. The circuit 204 uses the clock signal from the generator 208 to apply A/D-conversion to the luminance signal into a digital NTSC picture signal having a horizontal picture element number corresponding to a horizontal picture element number of a common intermediate format signal. Thus, the circuit is built up by using an inexpensive A/D converter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention converts analog NTSC image signals to H by the International Telegraph and Telephone Consultative Organization (CCITT).
An image format conversion circuit that converts to a common intermediate format signal for videophones and video conferences and that converts the common intermediate format signal back to an analog NTSC image signal based on the series recommendations. Regarding

[0002]

2. Description of the Related Art Conventionally, the following image signal transmission system has been proposed with reference to FIG.

That is, the analog N from the input terminal 11
The TSC image signal S1 (horizontal pixel number 384, horizontal line number 240) is sent to the digital NT in the A / D converter 12.
The image format conversion circuit 13 converts the digital NTSC image signal S2 into an SC image signal S2.
The common intermediate format signal S3 is converted into a common intermediate format signal S3 (horizontal pixel number 360 or 180, horizontal line number 288 or 144), and the common intermediate format signal S3 is encoded in the encoding circuit 14 by the encoding common intermediate format signal. The encoded common intermediate format signal S4 is encoded into S4.
Are transmitted to the transmission line 20 via the coupling circuit 15.

Further, the coded common intermediate format signal S4 'similar to the above-mentioned coded common intermediate format signal S4 from the transmission line 20 is received by the decoding circuit 16 via the coupling circuit 15, In the decoding circuit 16, the common intermediate format signal S4 'is converted into a common intermediate format signal S similar to the above-mentioned common intermediate format signal S3.
3 ', and the common intermediate format signal S3'
In the image format inverse conversion circuit 17, the same digital NT as the digital NTSC image signal S2 described above.
It is converted back to SC image signal S2 ', and its digital NTSC
The image signal S2 'is converted by the D / A converter 18 into an analog NT similar to the analog NTSC image signal S1 described above.
It is converted into the SC image signal S1 'and output to the output terminal 19.

[0005]

In the case of the conventional image format conversion circuit described above, in the A / D conversion circuit 14, the analog NTSC image signal is converted into the common intermediate format signal and the frequency of the number of horizontal pixels is set. According to 13.5MH
A / D conversion is performed using a sampling signal having a frequency of 1/2 or 1/4 of z, and vice versa, in the D / A conversion circuit 16, the common intermediate format signal S3 'is generated.
Similarly, a sampling signal having a frequency of 1/2 or 1/4 of 13.5 MHz according to the frequency of the number of horizontal pixels of the common intermediate format signal S3 'is used for the analog NTSC image signal S2'. It is designed for D / A conversion, and such 13.5MHz 1 /
The A / D conversion circuit 14 that performs A / D conversion using a sampling signal having a frequency of 2 or 1/4 and the D / A conversion circuit 16 that performs D / A conversion use the analog NTSC image signal as it is as a digital signal. For the NTSC image signal, 14.
A / D conversion circuit widely used for A / D conversion using a sampling signal having a frequency of 1/2 or 1/4 of 5 MHz, a digital NTSC image signal is directly converted into an analog NTSC image signal by D / D conversion. From the viewpoint of the D / A conversion circuit that is widely used for A conversion, the special A
The D / A conversion circuit and the D / A conversion circuit.

Therefore, the conventional image format conversion circuit has a drawback that it cannot be constructed inexpensively and easily.

Thus, the present invention does not have the above-mentioned drawbacks,
It proposes a new image format conversion circuit.

[0008]

The image format conversion circuit according to the first invention of the present application is (i) a common intermediate format.
An analog NTSC image signal converted to a matte signal,
A / D for converting into a first digital image signal using a sampling signal having a frequency according to the number of horizontal pixels
Converting means and (ii) the first digital image signal,
Means for obtaining each horizontal line as a second digital image signal having the number of horizontal pixels corresponding to the number of horizontal pixels of the common intermediate format signal; and (iii) the common digital signal from the second digital image signal. A third digital image signal having a horizontal line number corresponding to the horizontal line number of the intermediate format signal is obtained as the common intermediate format signal.

The image format conversion circuit according to the second aspect of the present invention is to convert the common intermediate format signal (i) converted into an analog NTSC image signal into the analog NT format image signal.
Means for obtaining a first digital image signal having a horizontal line number corresponding to the horizontal line number of the SC image signal;
(Ii) D / A conversion means for converting the first digital image signal into a first analog image signal by using a sampling signal having a frequency corresponding to the number of horizontal pixels of the analog NTSC image signal; iii) From the first analog image signal, each horizontal line corresponds to the analog NTS
The second analog image signal having the number of horizontal pixels corresponding to the number of horizontal pixels of the C image signal is converted to the analog NTSC.
And means for obtaining it as an image signal.

[0010]

According to the image format conversion circuit according to the first aspect of the present invention, the analog NTSC image signal is converted into the common intermediate format signal in the A / D conversion circuit.
A / D conversion is performed using a sampling signal having a frequency according to the frequency of the horizontal pixel number of the analog NTSC image signal, not the frequency according to the frequency of the horizontal pixel number, and such A / D The conversion circuit is widely used for A / D converting an analog NTSC image signal into a digital NTSC image signal as it is.
Since it is a conversion circuit, the A / D conversion circuit can be inexpensively and easily constructed, and therefore, the image format conversion circuit can be inexpensively and easily constructed.

According to the image format conversion circuit of the second aspect of the present invention, in the A / D conversion circuit,
The analog NTSC image signal is used as the common intermediate format signal, instead of the frequency corresponding to the frequency of the number of horizontal pixels.
A sampling signal having a frequency corresponding to the frequency of the number of horizontal pixels of the analog NTSC image signal is used for A / D conversion, and such an A / D conversion circuit
Converts analog NTSC image signals directly to digital NTS
A widely used for A / D conversion to C image signal
Since it is a / D conversion circuit, the A / D conversion circuit is inexpensive.
Therefore, the image format conversion circuit can be easily constructed at low cost.

[0012]

First Embodiment A first embodiment of an image format conversion circuit for converting an analog NTSC image signal into a common intermediate format signal according to the present invention will be described with reference to FIG.

The image format conversion circuit according to the present invention shown in FIG. 1 has the following configuration.

That is, the analog NTSC image signal S1
In the NTSC decoder 201, 1/2 or 1 / of 14.3 MHz from the clock signal generation circuit 208
Using a clock signal having a frequency of 4, the luminance signal S
Y and color difference signals SCr and SCb, and
The luminance signal SY is supplied to the A / D conversion circuit 204 through the bandpass filters 202 and 203 and the switch,
Then, in the A / D conversion circuit 204, the luminance signal SY ′ is supplied from the clock signal generator 208 by 14.3M.
A digital NTSC image signal having a horizontal pixel number corresponding to the horizontal pixel number of the common intermediate format signal, as shown in FIG. 3, using a clock signal having a frequency of 1/2 or 1/4 Hz. A / D conversion to.

On the other hand, the color difference signals SCr and SCb from the NTSC decoder 201 are respectively passed through bandpass filters 205 and 206 and a switch to obtain band-limited color difference signals SCr and SCb, which are multiplexed by a multiplexing circuit 207. , The multiplexed color difference signal SC is multiplexed into a digital color difference signal using the clock signal from the clock signal generator 208 in the A / D conversion circuit 207 '. / D conversion, and
Then, the digital image signal from the A / D conversion circuit 204 described above is multiplexed by the multiplexing circuit 209 into the multiplexed digital image signal.

Further, (i) the multiplexed digital image signal from the multiplexing circuit 209 and (ii) the digital image signal and the digital image signal obtained by passing the digital image signal through the line memory 210 are added in the adding circuit 212. Signal and (iii) the digital image signal passed through the line memory 210 and the digital image signal passed through another line memory 211.
The signal added by the addition circuit 213 with the TSC image signal and the digital N from the (iv) line memory 211.
By selecting the TSC image signal with the switching circuit, the common intermediate format from the digital NTSC image signal is selected.
Number of horizontal lines corresponding to the number of horizontal lines of mat signal 22
A digital NTSC image signal having 8 is obtained as a common intermediate format signal.

The above is the analog NTSC according to the present invention.
It is an embodiment of an image format conversion circuit for converting an image signal into a common intermediate format signal.

According to such an image format conversion circuit of the present invention, an analog NTSC image signal converted into a common intermediate format signal is converted into a sampling signal having a frequency corresponding to the number of horizontal pixels. , A / D conversion means for converting into a first digital image signal, and the number of horizontal pixels in which each horizontal line corresponds to the number of horizontal pixels of the common intermediate format signal in the first digital image signal. Means for obtaining as the second digital image signal, and
From the second digital image signal, the common intermediate fo
Means for obtaining, as the common intermediate format signal, a third digital image signal having the number of horizontal lines corresponding to the number of horizontal lines of the mat signal.

Therefore, in the A / D conversion means, the analog NTSC image signal is converted into a common intermediate format signal,
A sampling signal having a frequency corresponding to the frequency of the horizontal pixel number of the analog NTSC image signal, not the frequency corresponding to the frequency of the horizontal pixel number, is used for A / D conversion, and such A / D conversion is performed. The D conversion circuit is widely used for A / D converting an analog NTSC image signal into a digital NTSC image signal as it is.
Since it is a conversion circuit, the A / D conversion circuit can be inexpensively and easily constructed, and therefore, the image format conversion circuit can be inexpensively and easily constructed.

[0020]

[Embodiment 2] Next, an embodiment of an image format conversion circuit for inversely converting a common intermediate format signal into an analog NTSC image signal according to the present invention will be described with reference to FIG.

A common intermediate path according to the invention shown in FIG.
The image format conversion circuit for inversely converting the matte signal into the analog NTSC image signal is the image format conversion circuit described above with reference to FIG.
The common intermediate format signal similar to that obtained in the mat conversion circuit is input, and (i) the common intermediate format signal and the common intermediate format signal obtained by passing it through the line memory 301 are added. Common intermediate format signal obtained by adding in 304, (ii) common intermediate format signal obtained through the line memory 301, and common intermediate format signal obtained through the other line memory 302 And an addition common intermediate format signal obtained by adding and in another adder 305,
(Iii) The common intermediate format signal obtained through the line memory 303 and the common intermediate format signal
And a common intermediate format signal obtained through the addition in another adder 306 to obtain an added common intermediate format signal, and those signals are selected by a switch circuit to obtain the analog NTSC image signal. Digital N having 240 horizontal lines corresponding to the number of horizontal lines
Obtain a TSC image signal.

Further, the digital NTSC image signal is supplied to the time division demultiplexing circuit 307, the digital luminance signal SY 'and the digital color difference signal SC' are obtained from the time division demultiplexing circuit 307, and the digital luminance is obtained. In the D / A conversion circuit 308, the signal SY ′ is converted into 1/2 or 1 of the frequency of 14.3 MHz according to the number of horizontal pixels of the analog NTSC image signal from the clock signal generator 312.
A sampling signal having a clock signal having / 4 is used to convert the analog luminance signal S into a digital color signal SC ', and the D / A converter circuit 309' converts the analog color signal SC 'from the analog NTSC from the same clock signal generator 312. 1 at a frequency of 14.3 MHz according to the number of horizontal pixels of the image signal
The analog color signal SC is converted by using the sampling signal having the clock signal having / 2 or ¼, the analog color signal is supplied to the separation circuit 309, and the analog color difference signals SCr ′ and SCb ′ are supplied from the separation circuit 309. To get

Further, the analog luminance signal SY 'from the D / A conversion circuit 308 and the analog color difference signals SCr' and SCb 'from the separation circuit 309 are converted into a low-pass filter 310,
A clock signal generator 312 is provided through 311 and 312.
To the NTSC encoder 313 that operates using the clock signal CL from the NTSC encoder 313.
From the analog NTS input to the NTSC decoder of the image format conversion circuit according to the present invention described above with reference to FIG.
An analog NTSC image signal similar to the C image signal is obtained.

The above is an embodiment of the image format conversion circuit for inversely converting the common intermediate format signal into the analog NTSC image signal according to the present invention.

The common intermediate format according to the present invention is as follows.
An image format conversion circuit for inversely converting the matte signal into an analog NTSC image signal converts a common intermediate format signal converted into an analog NTSC image signal into horizontal lines corresponding to the number of horizontal lines of the analog NTSC image signal. Means for obtaining a first digital image signal having the number of lines, and the first digital image signal, the analog N
D / A conversion means for converting into a first analog image signal using a sampling signal having a frequency corresponding to the number of horizontal pixels of the TSC image signal, and from the first analog image signal, each horizontal line has the above analog Means for obtaining, as the analog NTSC image signal, a second analog image signal having a horizontal pixel number corresponding to the horizontal pixel number of the NTSC image signal.

Therefore, in the A / D conversion circuit, the analog NTSC image signal is converted into a common intermediate format signal,
A sampling signal having a frequency corresponding to the frequency of the horizontal pixel number of the analog NTSC image signal, not the frequency corresponding to the frequency of the horizontal pixel number, is used for A / D conversion, and such A / D conversion is performed. The D conversion circuit is widely used for A / D converting an analog NTSC image signal into a digital NTSC image signal as it is.
Since it is a conversion circuit, the A / D conversion circuit can be inexpensively and easily constructed, and therefore, the image format conversion circuit can be inexpensively and easily constructed.

In the above description, the image format conversion circuit for converting the analog NTSC image signal according to the present invention into the common intermediate format signal, and the common intermediate format.
For each of the image format conversion circuits for inversely converting the matte signal into the analog NTSC image signal, only one embodiment is shown, and various modifications and changes can be made without departing from the spirit of the present invention. It will be clear.

[Brief description of drawings]

FIG. 1 is a systematic connection diagram showing an embodiment of an image format conversion circuit for converting an analog NTSC image signal into a common intermediate format signal of an image format conversion circuit according to the present invention.

FIG. 2 is a systematic connection diagram showing an embodiment of an image format conversion circuit for converting a common intermediate format signal of an image format conversion circuit according to the present invention into an analog NTSC image signal.

FIG. 3 is a schematic diagram for explaining an image format conversion circuit according to the present invention.

FIG. 4 is a system diagram showing a conventional image signal transmission system.

[Explanation of symbols]

 11 Input Terminal 12 A / D Converter 13 Image Format Conversion Circuit 14 Encoding Circuit 15 Coupling Circuit 16 Decoding Circuit 17 Image Format Inversion Conversion Circuit 18 D / A Conversion Circuit 20 Transmission Line 201 NTSC Decoder 202 , 203 band-pass filter 204 A / D converter circuit 205, 206 band-pass filter 207 multiplexing circuit 208 clock signal generator 209 multiplexing circuit 312 clock signal generator 313 NTSC encoder

Claims (2)

[Claims] 1. An A / D converter for converting an analog NTSC image signal converted into a common intermediate format signal into a first digital image signal by using a sampling signal having a frequency corresponding to the number of horizontal pixels. Means for obtaining the first digital image signal as a second digital image signal in which each horizontal line has the number of horizontal pixels corresponding to the number of horizontal pixels of the common intermediate format signal; From the two digital image signals, the common intermediate format
An image format conversion circuit, comprising means for obtaining, as the common intermediate format signal, a third digital image signal having the number of horizontal lines corresponding to the number of horizontal lines of the mat signal. 2. Means for obtaining a common intermediate format signal converted into an analog NTSC image signal as a first digital image signal having a horizontal line number corresponding to the horizontal line number of the analog NTSC image signal. , The first digital image signal, the analog NTSC
D / A conversion means for converting into a first analog image signal using a sampling signal having a frequency corresponding to the number of horizontal pixels of the image signal, and from the first analog image signal, each horizontal line has the analog NTSC. An image format conversion circuit comprising: means for obtaining, as the analog NTSC image signal, a second analog image signal having the number of horizontal pixels corresponding to the number of horizontal pixels of the image signal.