JPH0833716B2 - Video signal converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a video signal converter for exchanging a high resolution RGB signal of a personal computer into an NTSC-compliant composite video signal.

<Prior Art> Generally, when a high resolution personal computer RGB signal having a horizontal frequency of 24 kHz or 31 kHz is converted into a composite video signal, the following is performed.

That is, for example, a high-resolution personal computer RGB signal having a system clock of 34 MHz, a horizontal frequency of 31 kHz, a horizontal image display period of 22 μsec, and a horizontal image display period of 53 μsec,
When converting to a composite video signal with a horizontal frequency of 15.75kHz, the system clock of 34MHz of the PC itself is a low-resolution system clock with a frequency (22/53) corresponding to the image display period, for example, 14.3MHz. And the PC RGB signal is D / A converted based on this system clock, and the horizontal frequency is about 15.75kHz along with the composite sync signal and burst flag pulse in the encoder circuit.
Is converted to a composite video signal of.

<Problems to be Solved by the Invention> However, in such a conventional conversion device, since the system clock of the personal computer itself must be converted to a low-resolution low-resolution system clock, the display on the personal computer side also Inevitably the display will have a low resolution, and since the obtained composite video signal is a non-interlaced scanning signal, this composite video signal is
When recorded on a video tape recorder or the like, there is a problem that color shift occurs.

The present invention has been made in view of the above points,
An object of the present invention is to provide a video signal conversion device capable of converting a high resolution personal computer RGB signal into an interlaced scanning composite video signal without changing the system clock of the personal computer itself to a low resolution system clock.

<Means for Solving the Problem> The present invention provides a high resolution RGB of a personal computer.
A signal converter for converting a signal to a composite video signal of NTSC system, which controls an output circuit and an output circuit for converting a non-interlaced RGB signal from a personal computer into an interlaced RGB signal and outputting the converted signal. A system control circuit that creates various signals necessary to form an NTSC composite video signal, and a D / A converter that converts the interlaced RGB signals output from the output circuit to D / A.
Based on analog RGB signals from the A conversion circuit and D / A conversion circuit and various signals from the system control circuit
And an encoder circuit that forms and outputs an NTSC composite video signal, and the system control circuit is an NT
Based on the horizontal / vertical sync signal generation circuit that generates the horizontal / vertical sync signal in the SC composite video signal, and the non-interlaced horizontal sync signal from the personal computer and the horizontal sync signal from the horizontal / vertical sync signal generation circuit. A high-resolution system clock of a personal computer and a PLL circuit that forms a video signalized clock having a predetermined frequency lower than the system clock, and a frequency divider circuit that forms a subcarrier clock based on the video signalized clock. A discriminating signal forming circuit for forming a field discriminating signal based on the vertical synchronizing signal from the horizontal / vertical synchronizing signal generating circuit, and a burst flag pulse based on the horizontal synchronizing signal from the horizontal / vertical synchronizing signal generating circuit Burst lag pulse generation circuit And a composite synchronizing signal generating circuit for a composite synchronizing signal generated based on the horizontal and vertical synchronizing signals from the signal generating circuit, the output circuit of the non-interlaced from the personal computer RGB
There is a switch circuit that selectively outputs the signal in even and odd fields based on the non-interlaced horizontal sync signal and vertical sync signal of the personal computer, and even and odd field data that is selectively output from the switch circuit. A plurality of field memories written separately, and data of each field memory are alternately transferred by the control clock from the personal computer and the field discrimination signal from the discrimination signal forming circuit, and by the video signalized clock from the PLL circuit. And a line memory for reading data and outputting the data to the D / A conversion circuit.

<Operation> According to the above configuration, in the output circuit, the field memory is used for conversion into interlaced scanning, and the clock is read from the line memory at a clock having a predetermined frequency lower than the system clock, that is, a low-resolution clock. Therefore, a composite video signal conforming to the interlaced NTSC system can be obtained without lowering the resolution of the system clock of the personal computer as in the conventional example.

<Examples> Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

 FIG. 1 is a block diagram of an embodiment of the present invention.

In the figure, 1 is a personal computer, and this personal computer 1
Is provided with an image memory 2 for writing or reading non-interlaced RGB signals, and a personal computer system control circuit 3 for controlling the writing or reading. The personal computer system control circuit 3 includes a frequency dividing circuit 22 and a memory. A control circuit 11 and an image output circuit 5 are provided.

4 is a high-resolution display dedicated to a personal computer, which is read from the image memory 2 and is given an RGB signal through the image output circuit 5 of the personal computer system control circuit 3,
Reference numeral 6 is a video signal conversion device according to the present invention.

The video signal converter 6 of this embodiment converts a 31 kHz high resolution RGB signal from the personal computer 1 into a composite video signal of NTSC system, and basically, a non-interlaced RGB signal from the personal computer 1. Interlaced RGB
An output circuit 7 for converting into a signal and outputting it, a system control circuit 8 for forming various clocks and the like, and controlling a memory of the output circuit 7, and an interlaced RGB signal from the output circuit 7 are D / A converted. A D / A conversion circuit 9 and an encoder circuit 10 that forms and outputs an NTSC composite video signal based on the analog RGB signal from the D / A conversion circuit 9 and various signals from the system control circuit 8. I have it.

The output circuit 7 switches the non-interlaced RGB signal read from the image memory 2 based on the non-interlaced horizontal synchronizing signal and vertical synchronizing signal from the memory control circuit 11 of the personal computer system control circuit 3. 12 and this switch circuit 12
Each pair of field memories 13a, b, 14a, b corresponding to even and odd fields in which RGB signals from or are written and read, and field memories 13a, b, 14a, b
And a line memory 15 to / from which the RGB signals from are written or read.

The system control circuit 8 corresponds to the memory control circuit 11 of the personal computer system control circuit 3
A non-interlaced horizontal sync signal of kHz and a 15.734kHz horizontal sync signal from the built-in horizontal / vertical sync signal generation circuit 16 are used to generate a video signal clock of 14.3MHz which is a predetermined frequency synchronized with the system clock of the personal computer 1. Based on the vertical synchronizing signal from the horizontal / vertical synchronizing signal generating circuit 16, the PLL circuit 17 that forms the dividing signal 18 that divides this video signalized clock to form a 3.58 MHz subcarrier clock. A discrimination signal forming circuit 19 for forming a field discrimination signal for discrimination, a burst flag pulse generating circuit 20 for generating a burst flag pulse based on the horizontal synchronizing signal from the horizontal / vertical synchronizing signal generating circuit 16, and a horizontal synchronizing signal. Sync signal generation circuit for generating a sync signal based on a signal and a vertical sync signal
It has 21 and.

The frequency of this video signal clock is 14.3MHz
As described in the prior art above, the PC and NTSC
It is based on the ratio (22/53) corresponding to the image display period.

Next, the operation of the video signal conversion device 6 having the above configuration will be described.

Now, the personal computer 1 side has a high-resolution system clock,
For example, it is operating at 34 MHz, and the RGB signals are written in and read from the image memory 2 by the memory control circuit 11 based on this system clock. The read RGB signal is branched and given to the dedicated display 4 via the image output circuit 5 to be displayed in high resolution.

On the other hand, the RGB signal given to the video signal converter 6 is
The switch circuit 12 switches alternately in response to the horizontal synchronizing signal, writes the data in one odd field memory 14a (14b) and one even field memory 13a (13b), and after applying the vertical synchronizing signal, the other Odd field memory 14b (14a) and the other even field memory 13
It is written alternately in b (13a), and the same operation is repeated thereafter.

The transfer of data from the field memories 13a, b, 14a, b to the line memory 15 is performed by the data of one odd field memory 14a (14b) by the control clock of 17MHz and the field discrimination signal from the personal computer system control circuit 3. Is read and written in the line memory 15, and is read from the line memory 15 at 14.3 MHz which is a video signalized clock and given to the D / A conversion circuit 9.

When the transfer of data for one field is completed, next,
Similarly, the data in one of the even field memories 13a (13b) is read out and written in the line memory 15, and further read out from the line memory 15 at the video signal clock.

Similarly, the other odd field memory 14b (14a)
Data of the other even field memory 13b (13a) and the other data are sequentially transferred alternately for each field.

The RGB signal thus converted into the interlace is converted into an analog RGB signal by the D / A conversion circuit 9, and further, by the encoder circuit 10, the composite sync signal, the burst flag pulse, and the subcarrier clock are applied to the NT signal.
It is output as an SC composite video signal.

In this way, the high resolution RGB signal from the personal computer 1 is interlaced while the personal computer 1 side is operating with the high resolution system clock, that is, the display 4 is still displaying the high resolution image. NTSC
It becomes possible to convert into a composite video signal conforming to the method, and thus, even when recording with a video tape recorder, there is no occurrence of color misregistration.

In the above-mentioned embodiment, the video signal clock of the predetermined frequency is set to 14.3 MHz, but this is defined by the ratio (22/53) corresponding to the image display period between the personal computer and the NTSC as described above. Therefore, when this ratio is different, the frequency division ratio in the frequency dividing circuit 18 is changed accordingly.

<Advantages of the Invention> As described above, according to the present invention, the field memory is used for conversion into interlaced scanning, and the line memory is read with a clock having a predetermined frequency lower than the system clock, that is, a low-resolution clock. Therefore, it is possible to obtain a composite video signal conforming to the interlaced NTSC system without lowering the resolution of the system clock of the personal computer as in the conventional example. In other words, the personal computer side can be kept operating with the high-resolution system clock, so that the high-resolution video of the personal computer is displayed on the display connected to the personal computer, and the video is displayed on the personal computer. A video tape recorder for recording NTSC composite video signals that is connected to can be recorded clearly without color shift. As described above, according to the present invention, it becomes possible to improve the usability such as the peripheral devices of the personal computer can be effectively used.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention. 1 ... Personal computer, 6 ... Video signal conversion device, 7 ... Output circuit, 8 ... System control circuit, 9 ... D / A conversion circuit, 10 ... Encoder circuit.

Claims (1)

[Claims] 1. High resolution RGB of a personal computer
A video signal converter that converts a signal into a composite video signal of NTSC system, which is a non-interlaced RG from a personal computer.
An output circuit that converts the B signal into an interlaced RGB signal and outputs it, a system control circuit that controls the output circuit and creates various signals necessary to form an NTSC composite video signal, and an output circuit D / A conversion circuit that performs D / A conversion of interlaced RGB signals
It has an encoder circuit that forms and outputs an NTSC composite video signal based on the analog RGB signal from the conversion circuit and various signals from the system control circuit, and the system control circuit is an NTSC composite video signal. A horizontal / vertical synchronizing signal generating circuit for generating a horizontal / vertical synchronizing signal, and a high resolution system for a personal computer based on the non-interlaced horizontal synchronizing signal from the personal computer and the horizontal synchronizing signal from the horizontal / vertical synchronizing signal generating circuit. A PLL circuit which is synchronized with the clock and forms a video signalized clock having a predetermined frequency lower than the system clock, a frequency divider circuit which forms a subcarrier clock based on the video signalized clock, and the horizontal / vertical synchronization signals. Based on the vertical sync signal from the generator circuit, From the horizontal / vertical sync signal generation circuit, and a burst flag pulse generation circuit that generates a burst flag pulse based on the horizontal sync signal from the horizontal / vertical sync signal generation circuit. And a composite sync signal generating circuit for generating a composite sync signal based on a horizontal sync signal and a vertical sync signal, wherein the output circuit outputs a non-interlaced RGB signal from a personal computer to a non-interlaced horizontal sync of the personal computer. A switch circuit that selectively outputs even-numbered and odd-numbered fields based on a signal and a vertical synchronization signal, and a plurality of field memories that individually write the even-numbered and odd-numbered field data that are selectively output from the switch circuit. Field memory data is personal computer The data is read by the video signal of the clock from the PLL circuit while being transferred alternately by the control clock and field discriminating signal from said discriminating signal forming circuit from the D /
A video signal conversion device comprising: a line memory for outputting to an A conversion circuit.