JP2002271755A - Digital blanking signal generator - Google Patents

Abstract

(57) [Problem] To provide a digital blanking signal generating device which does not significantly increase the circuit amount by configuring the data amount of a waveform shape ROM table to be small. SOLUTION: A storage means 102 for storing a quantized waveform data value based on an information logic signal 101 of data "1" or "0" to be superimposed, and a phase difference between a main clock and a signal to be generated. It is provided with a superimposed waveform generator 103 for generating the frequency of the signal to be generated by a calculation based on the digital signal, and generates a digital signal waveform having a frequency not synchronized with the main clock operating digitally.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital blanking signal generator for generating a blanking signal in a digital LSI, and particularly to a blanking signal having a frequency different from the main clock frequency. And a frequency signal.

[0002]

2. Description of the Related Art In the transmission of a television signal, various information signals such as a character signal and a control signal are transmitted while being superimposed on a vertical blanking signal in a vertical blanking period. The information signal can be transmitted / received by the device on the transmitting side of the television signal and detected by the device on the receiving side to detect and transmit the information signal.

[0003] A transmission method of the information signal according to the prior art will be described below. FIG. 3 is a diagram showing a configuration of a conventional digital blanking signal generator. As shown in the figure, the waveform shape ROM table 303,
306, 309 and the waveform shape ROM table 30
Superimposed waveform generating circuits 302, 305, and 308 respectively receiving the outputs of 3, 306, and 309; an adder 310 that adds signals from the plurality of generating circuits; An adder 312 that adds the waveform generation signal and a DA conversion circuit 313 that converts the output of the adder 312 to analog are provided.

A logic signal of information to be superimposed is input to a terminal 301 from a microcomputer or the like, and an information logic signal A such as VideoID, closed caption, VITC or WSS is input to a superimposed waveform generation circuit 303. Based on the input logic signal, a waveform is generated in the superimposed waveform generation circuit 302 using information of data stored in the waveform shape ROM table 302. Similarly, the superimposed waveform generating circuits 305 and 308 receive information logic signals B and C, respectively, and generate waveforms of information such as VideoID, closed caption, VITC, and WSS.

The plurality of superimposed waveform generating circuits 302, 3
05, 308 are added by an adder 310 to obtain a video ID, a closed caption, and a VIT.
It becomes a plurality of superimposed waveforms such as C and WSS.

Next, the generated plurality of superimposed waveforms and the digital video luminance signal 311 are added in an adder 312, whereby a vertical blanking signal is generated in the vertical blanking period by the adder 312. The superimposed waveform is superimposed, and finally, the digital signal is converted into an analog signal by the DA conversion circuit 313 and output as an analog television luminance signal.

FIG. 9 shows an example of this television signal. In FIG. 9, reference numeral 901 denotes a horizontal line number, 902 denotes a VITC, 903 denotes a Video ID, 904 denotes a closed caption, and 905 denotes a video luminance signal.
As described above, the conventional digital blanking signal generator generates a television luminance signal including a plurality of superimposed blanking waveforms.

Hereinafter, a detailed description will be given for generating a digital blanking signal. Table 1 shows an example of the contents of the waveform shape ROM tables 303, 306, and 309 in FIG. As shown in Table 1, data 1 and data 2 corresponding to addresses are stored in a table format. Here, the address is data on the time axis, and the data 1 and data 2 are data in the amplitude direction. FIG. 5 is a graph of Table 1.

As can be seen from FIG. 5, the ROM table is obtained by sampling a superimposed waveform to be generated. This waveform shape ROM table 303, 306, 3
09, the superimposed waveform generation circuit 302 uses the waveform shape RO
An address of the M table 303 is generated, and a determination is made as to whether to use the data of the series of data 1 or data 2 based on the logical value of the information logic signal A (301). Read data. By performing this operation continuously for each main clock, a superimposed waveform can be generated.

[0010]

[Table 1] FIG. 6 expresses the concept of the above operation. As shown in FIG. 6, (a) shows an information logic signal such as 301, and (b) shows a waveform of an analog television luminance signal converted into an analog signal by the D / A conversion circuit 313.

As described above, various information signals such as a character signal and a control signal are superimposed in the vertical blanking period by the digital blanking signal generator according to the prior art, thereby containing various kinds of vertical blanking information. Television signals can be transmitted.

The digital blanking signal generating apparatus according to the prior art has been described above. Next, a basic technique of the present invention for generating an information signal having a frequency different from the frequency of the main clock will be described. . Here, description will be made using an example of a digital chroma encoder. The technology of digital chroma encoder is disclosed in
This is known from Japanese Patent Application Laid-Open Nos. 069379 and 08-107564.

Video data conforming to the digital CCIR 601 system is transmitted to the NTSC system, the PAL system, and the SECA system.
2. Description of the Related Art A digital chroma encoder that generates a video chroma signal corresponding to a second television format from a video signal corresponding to a first television format, such as conversion into an analog baseband signal such as the M format, is known. . Here, in a television system such as the NTSC system,
The color difference signal is subjected to balanced modulation called quadrature two-phase modulation at a predetermined color subcarrier frequency.
Therefore, in the above-described video encoder, the balanced modulation circuit is provided to generate a carrier chrominance signal obtained by performing balanced modulation on the color difference signal.

For example, the color difference signals Cr and Cb of digital video data conforming to the CCIR
A balanced modulation circuit (digital chroma encoder) that generates a carrier chrominance signal of a system or the like is configured as shown in FIG.

The balanced modulation circuit shown in FIG.
A level conversion circuit 404 to which color difference signals Cr and Cb of video data conforming to the first system are supplied; a synchronization signal generation circuit 401 for generating a synchronization signal; and a synchronization signal generation circuit 4
A sub-carrier generation circuit 403 for generating sub-carriers based on the synchronization signal from the sub-carrier generation unit 403; A quadrature two-phase modulation circuit 40 that performs two-phase modulation and generates a carrier color signal
5 is provided. The level conversion circuit 404 corrects, for example, because the level of the color difference signal is different between the CCIR601 system and the NTSC system.

The quadrature two-phase modulation circuit 405 performs quadrature two-phase modulation on the level-converted color difference signals Cr and Cb. For example, in the NTSC system, the level-converted color difference signals Cr and Cb are separately amplitude-modulated by two subcarriers having a frequency of about 3.58 MHz and a phase difference of 90 °. Then, the two modulated outputs are combined and output as one signal. Quadrature two-phase modulation circuit 40
5 outputs the composite output as a carrier color signal.

As described above, the balanced modulation circuit shown in FIG. 4 can generate the CCIR 601 video data and the carrier color signal of the NTSC system or the like which is not synchronized with the main clock of the video data.

[0018]

The conventional digital blanking signal generator is configured as described above, and the waveform shape ROM table as the data storage device requires a large circuit scale. For each generated signal, for example, with blanking information such as VideoID, closed caption, VITC, WSS, etc., each time the frequency of the information signal is different, a plurality of waveform shape ROM tables and a plurality of superimposed waveform generating circuits are required. There was a problem of becoming large.

The present invention has been made to solve the above problems, and has as its object to provide a digital blanking signal generator having a smaller circuit scale.

[0020]

According to a first aspect of the present invention, there is provided a digital blanking signal generating apparatus which stores a quantized waveform data value, and calculates a signal frequency to be generated by a calculation. And superimposed waveform generating means for reading out the quantized waveform data from the storage means and superimposing it on a logic signal for obtaining a desired waveform to generate a digital signal waveform.

In a digital blanking signal generator according to a second aspect of the present invention, in the digital blanking signal generator according to the first aspect, the storage means stores the waveform data to be generated by storing the waveform data of the waveform data. It is stored as a quantized sampling data value for one cycle.

According to a third aspect of the present invention, there is provided a digital blanking signal generator according to the first aspect, wherein the storage means comprises:
The waveform data to be generated is stored as a quantized sampling data value for a quarter cycle of the waveform data, and the superimposed waveform generating means calculates by calculation the data for the quarter cycle. And a circuit for converting the data into data for one cycle.

The digital blanking signal generator according to claim 4 of the present invention is the digital blanking signal generator according to claim 1, wherein the logic signal "1" or "1" for obtaining the desired waveform is provided. There is provided a level conversion circuit for converting the information data of "0" into a video signal format having a predetermined gradation, and the superimposed waveform generating means superimposes the signal after the level conversion in a vertical blanking period.

According to a fifth aspect of the present invention, there is provided a digital blanking signal generator according to any one of the first to fourth aspects, wherein the digital blanking signal is superimposed on a vertical blanking period. It modulates information data of a signal "1" or "0" for obtaining a waveform, and outputs a waveform having an arbitrary shape such as a sine waveform or a trapezoidal waveform.

According to the digital blanking signal generator according to claim 6 of the present invention, claims 1 to 5 are provided.
In the digital blanking signal generator according to any one of the above, the superimposing waveform generating means superimposes a signal for obtaining a single or plural kinds of desired waveforms in the vertical blanking period.

[0026]

(Embodiment 1) A digital blanking signal generator according to Embodiment 1 of the present invention will be described below with reference to FIG. In FIG.
101 is an information logic signal of "1" or "0" for generating data to be superimposed, and 102 is a waveform shape ROM table storing waveform shape data.

A superimposed waveform 103 includes means for generating a frequency of a signal to be generated by calculating a phase difference obtained according to a ratio between a sampling frequency of a main clock and a frequency of a signal to be superimposed. Generating circuit 103
The predetermined data is read from the waveform shape ROM table 102 on the basis of the above calculation result, and the data is superimposed on the information logic signal 101. Generates an information signal.

The various information signals such as the generated character signals and control signals are added to the digital video luminance signal 104 by the adder 105, and the above-mentioned various control information signals are vertically blanked during the vertical blanking period. After superimposing on the signal, D
Is converted into an analog signal by the / A conversion circuit 106,
An analog television luminance signal including various information signals such as a character signal and a control signal to be superimposed on the vertical blanking is generated.

ROM table 10 for storing waveform shapes used when generating the digital blanking signal
Table 2 shows an example of the data of No. 2 and FIG. 7 shows a graph of Table 2.

[0030]

[Table 2] As is apparent from FIG. 7, this ROM table is
As a quantization time of waveform data to be generated, a sampling data value for one cycle of the waveform data is stored.

In order to reduce the amount of data in the ROM table, when quantizing the waveform data, the error between the required waveform shape and the ideal shape is within an allowable range, and the quantization may be performed in a long time. Quantization with gradation is performed.

The amplitude of the digital blanking signal to be superimposed is required for amplitude conversion by providing the amplitude value itself in the waveform shape ROM table when there is only one type of information logic signal as in the present embodiment. The value of the amplitude can be determined without using a multiplier. It is needless to say that the configuration using the multiplier has the same function.

As described above, according to the present embodiment, one cycle of the waveform data to be generated is quantized, and the sampling data is stored in the waveform shape ROM table 102. The above waveform shape ROM based on the phase difference with the frequency to be made
Since various information signals are generated by reading data having a desired amplitude value from the table 102 and superimposing the data on the information logic signal 101, the data amount stored in the waveform shape ROM table 102 can be reduced. In addition, the number of superimposed waveform generation circuits can be reduced, and the circuit scale can be reduced.

Although the present embodiment has been described with reference to a waveform having a trapezoidal shape as an example, the waveform may be changed to an arbitrary waveform such as a sine waveform or a trapezoidal waveform according to the data set in the waveform shape ROM table. It is also possible to generate a shaped digital blanking signal.

(Embodiment 2) Next, a blanking signal generator according to Embodiment 2 of the present invention will be described.

In the second embodiment, the configuration is the same as that of the first embodiment. However, in the first embodiment, a ROM table for storing a waveform shape used when generating a digital blanking signal is generated. As the waveform data to be stored, a quantized data value obtained by sampling the waveform data for one cycle is stored.
In the second embodiment, as shown in FIG. 10, a sample of waveform data to be generated is stored in a waveform shape ROM for storing sampling data values for a quarter cycle of the waveform data.
The difference is that a table 102a is provided.

Waveform Shape ROM in Second Embodiment
Table 3 shows an example of the table, and FIG. 8 shows a graph of the table 3. Referring to FIG. 8, the waveform shape ROM
It can be seen that the table stores data for a quarter cycle of the ROM table of FIG. By taking advantage of the fact that the actual waveform has this repetitive shape, a plus / minus sign and information on the phase difference are added to the data of this quarter cycle to perform an arithmetic operation. Waveform data of one cycle of data can be created from one cycle of data.

As described above, according to the second embodiment, one-fourth cycle of the quantized data of the waveform data to be generated is stored in the waveform shape ROM table, and one cycle of the waveform data is calculated by the arithmetic processing. Since the generation is performed, the amount of data stored in the waveform shape ROM table can be further reduced as compared with the first embodiment, and the circuit scale can be further reduced.

Third Embodiment Next, a digital blanking signal generator according to a third embodiment of the present invention will be described with reference to FIG. In FIG. 2, 201, 202,
Reference numeral 203 denotes an information logic signal of “1” or “0” for generating data to be superimposed, and the level conversion circuit 204 converts the information logic signal into information having an amplitude of a digital blanking signal to be superimposed. Logic signal 20
Level conversion is performed for each of 1, 202, and 203. Then, based on the level-converted signal, the waveform shape data stored in the waveform shape ROM table 205 is used in accordance with the ratio between the sampling frequency of the main clock and the frequency for each type of signal to be superimposed. Using the obtained coefficient,
By reading a signal of a predetermined amplitude by the superimposed waveform generation circuit 206, various information signals such as a character signal superimposed on the vertical blanking and a control signal are generated. The generated various information signals and the digital video luminance signal 207 are added by an adder 208. In the vertical blanking period, the various information signals are superimposed on the vertical blanking signal, and then the D / A The signal is converted into an analog signal by the conversion circuit 209 and becomes an analog television luminance signal in which various information signals such as a character signal and a control signal are superimposed on vertical blanking.

A waveform shape ROM used in the third embodiment
An example of the contents of the table 205 is the same as that of Table 2 described in Embodiment 1 and FIG. 7, and is shared by a plurality of digital blanking signals to be superimposed. In order to perform this sharing, it is necessary that a plurality of digital blanking signals to be superimposed have the same shape. The amplitude and frequency can be set for each of a plurality of digital blanking signals to be superimposed.

As described above, according to the third embodiment, the level conversion circuit 2 receiving the plurality of logic signals 201 to 203
In FIG. 9, each logic signal is level-converted and supplied to the superimposed waveform generation circuit 206 so as to have the amplitude of the digital blanking signal to be superimposed. A plurality of digital blanking signals such as VideoID, closed caption, VITC, and WSS can be superimposed on the vertical blanking signal in the vertical blanking period.

(Embodiment 4) Next, a digital blanking signal generator according to Embodiment 4 of the present invention will be described. The fourth embodiment has the same basic configuration as the configuration of the third embodiment shown in FIG. 2, but as shown in FIG. 11, the waveform shape stored in the waveform shape ROM table 205a is The waveform data to be generated is stored as a quantized sampling data value for one quarter of the waveform data.

That is, the ROM table 205a storing the waveform shapes used in the fourth embodiment is the same as Table 3 described in the second embodiment and FIG. Shared with blanking signal. In order to perform this sharing, it is necessary that a plurality of digital blanking signals to be superimposed have the same shape. The amplitude and frequency can be set for each of a plurality of digital blanking signals to be superimposed.

As described above, according to the fourth embodiment, level conversion circuit 2 receiving a plurality of logic signals 201 to 203
In FIG. 9, each logic signal is level-converted so as to have the amplitude of a digital blanking signal to be superimposed, and then supplied to the superimposed waveform generation circuit 206. , VideoID, closed caption, VITC, WSS, etc., and in addition to superimposing information on a plurality of digital blanking signals, the capacity of the waveform ROM table is reduced as compared with the third embodiment. can do.

[0045]

As described above, according to the digital blanking signal generator according to the first aspect of the present invention, the storage means for storing the quantized waveform data value and the signal frequency to be generated are obtained by calculation. And superimposed waveform generating means for reading desired quantized waveform data from the storage means and superimposing the read data on a logic signal for obtaining a desired waveform to generate a digital signal waveform. Therefore, an effect is obtained that a digital blanking signal generator for various information signals such as a character signal having a frequency not synchronized with the digitally operated main clock and a control signal can be realized.

According to a digital blanking signal generator according to a second aspect of the present invention, in the digital blanking signal generator according to the first aspect, the storage means stores the waveform data to be generated, Since the information is stored as a quantized sampling data value for one cycle of data, various information signals such as a character signal and a control signal are superimposed on the vertical blanking period to obtain various types of vertical blanking information. There is an effect that it is possible to realize a digital blanking signal generation device capable of transmitting a television signal including the following.

According to a third aspect of the present invention, in the digital blanking signal generator according to the first aspect, the storage means stores the waveform data to be generated in the digital blanking signal generator. The waveform data is stored as a quantized sampling data value for one quarter cycle of the waveform data, and the superimposed waveform generating means converts the data for one quarter cycle to data for one cycle by calculation. The superimposition of various information signals such as a character signal and a control signal in the vertical blanking period has an effect that the capacity of the waveform ROM table can be further reduced.

The digital blanking signal generator according to claim 4 of the present invention is the digital blanking signal generator according to claim 1, wherein the logic signal "1" or "1" for obtaining the desired waveform is provided. A level conversion circuit for converting the information data of "0" into a video signal format having a predetermined gradation; and the superimposing waveform generating means superimposing the signal after the level conversion in a vertical blanking period. There is an effect that a plurality of information logic signals can be superimposed.

According to a fifth aspect of the present invention, there is provided a digital blanking signal generator according to any one of the first to fourth aspects, wherein the digital blanking signal is desired to be superimposed on a vertical blanking period. Since the information data of the signal "1" or "0" for obtaining a waveform is modulated and a waveform having an arbitrary shape such as a sine waveform or a trapezoidal waveform is output, a digital block having an arbitrary waveform shape is output. There is an effect that a ranking signal can be generated.

According to the digital blanking signal generator according to claim 6 of the present invention, claims 1 to 5 are provided.
In the digital blanking signal generating device according to any one of the above, the superimposed waveform generating means, so as to superimpose a signal for obtaining a single or a plurality of types of desired waveform in the vertical blanking period, VideoID
Shape information, which is a basic element of this device, for multiple blanking information with different amplitudes and frequencies of information signals, such as data, closed captions, VITC and WSS.
Since the table and the superimposed waveform generation circuit can be shared, the circuit size can be further reduced, and an inexpensive digital blanking signal generator can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a digital blanking signal generator according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a digital blanking signal generator according to a third embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a conventional digital blanking signal generator.

FIG. 4 is a diagram showing a conventional digital blanking signal generator, which uses NTSC from a color difference signal of digital video data.
FIG. 3 is a diagram illustrating a configuration of a balanced modulation circuit that generates a carrier chrominance signal of a system or the like.

FIG. 5 is a diagram illustrating a waveform chart of a ROM data table of a superimposed waveform to be generated in a conventional digital blanking signal generator.

FIG. 6 is a diagram conceptually showing an operation of generating a superimposed waveform from an information logic signal in the digital blanking signal generator.

FIG. 7 is a diagram illustrating a waveform chart of a waveform shape ROM table of the digital blanking signal generator according to the first embodiment.

FIG. 8 is a diagram showing a waveform chart of a waveform ROM table of the digital blanking signal generator according to the second embodiment.

FIG. 9 is a diagram of a television luminance signal waveform including a plurality of superimposed blanking waveforms according to the related art and the present invention.

FIG. 10 is a diagram illustrating a configuration of a digital blanking signal generator according to a second embodiment of the present invention.

FIG. 11 is a diagram showing a configuration of a digital blanking signal generator according to a fourth embodiment of the present invention.

[Explanation of symbols]

 101 information logic signal 102, 102a waveform shape ROM table 103 superimposed waveform generation circuit 104 digital video luminance signal 105 adder 106 D / A conversion circuit 201, 202, 203 information logic signal 204 level conversion circuit 205, 205a waveform shape ROM table 206 Superimposed waveform generation circuit 207 Digital video luminance signal 208 Adder 209 D / A conversion circuit 301, 304, 307 Information logic signal 302, 305, 308 Superimposed waveform generation circuit 303, 306, 309 Waveform shape ROM table 310 Adder 311 Digital video Luminance signal 312 adder 313 D / A conversion circuit 401 synchronization signal generation circuit 402 quadrature two-phase modulation SIN waveform ROM table 403 subcarrier generation circuit 404 level conversion circuit 405 quadrature two-phase modulation circuit 901 horizontal line Version number 902 VITC 903 VideoID 904 closed caption 905 video signal

Claims (6)

[Claims] 1. A storage means for storing a quantized waveform data value, a signal frequency to be generated is obtained by calculation, and a desired quantized waveform data is read from the storage means.
A digital blanking signal generating device, comprising: superimposed waveform generating means for generating a digital signal waveform by superimposing the digital blanking signal on a logic signal for obtaining a desired waveform. 2. The digital blanking signal generator according to claim 1, wherein the storage means stores the waveform data to be generated as a quantized sampling data value for one cycle of the waveform data. A digital blanking signal generator. 3. The digital blanking signal generator according to claim 1, wherein said storage means stores the waveform data to be generated as a quantized sampling data value for a quarter cycle of the waveform data. A digital blanking signal generator, characterized in that the superimposed waveform generating means includes a circuit for converting the data of the quarter cycle into the data of one cycle by calculation. 4. The digital blanking signal generator according to claim 1, wherein the information data of the logical signal “1” or “0” for obtaining the desired waveform is a video signal format having a predetermined gradation. A digital blanking signal generating device, comprising: a level conversion circuit for converting the signal into a blanking signal; and the superimposing waveform generating means superimposing the signal after the level conversion in a vertical blanking period. 5. The digital blanking signal generator according to claim 1, wherein information data of a signal “1” or “0” for obtaining a desired waveform superimposed in a vertical blanking period. A digital blanking signal generator characterized in that the digital blanking signal is generated by outputting a waveform having an arbitrary shape such as a sine waveform or a trapezoidal waveform. 6. A digital blanking signal generator according to claim 1, wherein said superimposed waveform generating means converts a signal for obtaining a single or a plurality of types of desired waveforms into a vertical blanking signal. A digital blanking signal generator, which is superimposed on a ranking period.