JP3261806B2 - Color system discrimination circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color system discriminating circuit for a television receiver capable of multi-system reception.

[0002]

2. Description of the Related Art In recent years, television receivers have become very popular in the world market. On the other hand, video sources are also diversified such as video tape recorders, video disc players, personal computers, etc., and multi-system television receivers capable of receiving various types of broadcasting systems have been developed.

[0003] The multi-method means PAL / SECAM / NTS.
NTSC with C / chroma signal modulated to 4.43 MHz
It is a method.

In the NTSC system in which a chroma signal is modulated to 4.43 MHz, a chroma signal is demodulated at 4.43 MHz when a video tape recorded in NTSC is reproduced by a PAL video tape recorder. .
After that, the NTSC where the chroma signal was modulated at 4.43 MHz
The system is the NTSC 4.43 system, and the original NTSC system is
NTSC to distinguish from the NTSC 4.43 system
We will call it the 3.58 system.

[0005] To receive signals of these multiple systems, a color signal demodulation circuit corresponding to each system is required. A method has been considered in which a circuit automatically determines and sets a television system in order to eliminate the complexity of a user switching circuits in accordance with each system. For example, JP
The -10988 has a chrominance subcarrier generation circuit, performs synchronous detection while switching its phase, and distinguishes between the PAL system and the NTSC system based on the information of the synchronous detection.

[0006]

However, in the above-mentioned conventional configuration, a chrominance subcarrier generation circuit, a detection circuit, and the like are indispensable for discriminating the television system. Also, the more the types are determined, the more the number of determination circuits is required.

[0007]

In recent years, most television receivers have a built-in control microcomputer for controlling their functions. Solving the above issues
The color system determination circuit of the present invention uses a microcomputer incorporated in the television receiver to periodically switch the television system and determine whether the set system is correct based on color killer voltage information. A PAL system and a SECAM system.
System, NTSC system, chroma signal is 4.43MHz
Four types of color television with the modulated NTSC system
Receiving circuit for receiving a television signal, and each television of the receiving circuit
The color demodulation circuit of the system selected and set by switching the system circuit
Of the color killer signal based on the color killer voltage information
Determine the presence or absence and set the TV signal circuit switching setting of the received signal.
The vertical video frequency is
If a 60 Hz PAL signal is input,
Even if the receiving circuit is switched and set to the PAL circuit
Modulated NTSC with chroma signal modulated to 4.43 MHz
Color killer signal is output even in the system circuit
In the system determined to be present, the microcomputer
Set a certain time after switching the TV system circuit
To set the color killer signal
When determining whether the PAL method is correct, set the PAL method first.
And check the color killer signal.
The signal is modulated with a 4.43 MHz modulated NTSC system
Color killer signal by setting the NTSC system
Check, if the chroma signal is 4.43 MHz modulated NTS
C signal or unmodulated NTSC or chroma signal
Checks whether the system is a 4.43 MHz modulated NTSC system
To determine the correct TV system and select the receiving circuit.
It's something that has been done.

[0008] That is, after switching to the television system switching circuit, if a certain waiting time is provided and color killer voltage information (the presence or absence of a color killer signal) is checked, it is determined whether the set system is correct. Focusing on what can be done, the function is realized by the software of the control microcomputer built into the television receiver. When a PAL signal having a vertical video frequency of 60 Hz is input, the characteristics of the circuit include a PAL system and NTSC 4.4.
Although a color killer signal is present in any of the three types of circuit settings, the present invention always checks from the PAL type setting when the TV channel is switched or the TV / video screen is switched. To prevent malfunction.

The PAL signal of 60 Hz is obtained when a video tape recorded in NTSC is reproduced by a PAL video tape recorder. Here, when the tape is fast-forward-reproduced, the characteristics of the PAL signal are as follows.
NTSC system signal is input.
A color killer signal is not present unless the circuit is set to the 4.43 system.

Therefore, in order to prevent this malfunction, once it is determined that there is a color killer signal in the setting of the PAL system at a vertical video frequency of 60 Hz, even if there is no color killer signal, the NTSC 4.43 system is set. , P
An algorithm for judging the television system only by setting the AL system or SECAM and the NTSC 3.58 system is introduced.

When a SECAM signal is input, a color killer signal may be present even when the NTSC 3.58 system is set as a circuit characteristic. In order to prevent this malfunction, an algorithm is introduced that does not check the SECAM setting when a signal having a vertical video frequency of 60 Hz is input.

[0012]

As described above, according to the present invention, a unique case in which the determination cannot be made by simply setting the television system and determining the result by the color killer signal can be solved by the software algorithm.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments shown in the drawings.

FIG. 1 is a block diagram showing a color system discriminating circuit according to one embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a control microcomputer built in a television receiver. 2 is a video chroma IC, and 3 is a SECAM decode IC.

In this embodiment, the video chroma IC is A
N5606, AN563 as SECAM decode IC
6 is used. These ICs are all manufactured by Matsushita Electronics Corporation. The video chroma IC 2 has a built-in receiving circuit of the PAL system, the NTSC 3.58 system, and the NTSC 4.43 system, and can switch between them by externally accessing the internal register via the IIC bus.

When a SECAM signal is input, the SECAM decode IC 3 converts the signal into a PAL signal and outputs the signal. When a signal other than the SECAM signal is input, the signal is output through. Also, this SECAM
When the signal of the SECAM system is input, the decode IC 3
An ECAM presence signal ("L" level output) is output. As shown in FIG. 1, in the configuration of the circuit of the present invention, PAL system, NTSC 3.58 system, NTS
Any signal of the C4.43 system will be input.

The microcomputer 1 performs PAL / NTSC system switching and 3.58 /
The clock of 4.43 MHz is switched. These switching are performed via the IIC bus.

When setting the PAL system, clock = 4.43 MHz is selected in the PAL setting. NTSC 4.4
When setting 3 systems, set the clock =
Select 4.43 MHz. When setting the NTSC 3.58 method, set the clock to 3.58 MH in the NTSC setting.
Select z.

The microcomputer 1 has a video chroma IC 2
, The information on whether the vertical frequency of the video signal is 50 Hz or 60 Hz ("L" at 50 Hz) and the information on the presence or absence of a color killer signal ("L" when present) are input to the input port.

By the way, as described above, the video chroma I
Since C2 can set only one of PAL / NTSC3.58 / NTSC4.43, the microcomputer 1
Whether the setting is AM or not, SE of 3 SECAM decode IC
The state of the CAM signal presence / absence output terminal is monitored to make a determination.

FIG. 2 is a flowchart showing the basic operation of the microcomputer 1 in the circuit of the present invention. 3 and 4 are flowcharts showing the detailed operation of the microcomputer 1 in the circuit of the present invention.

In FIG. 2, when switching channels or screens, the microcomputer 1 first sets the system = PAL and the clock = 4.43 (referred to as output mode 1) to the video chroma IC 2.

After a waiting time of 90 msec until the response of the circuit to the setting is stabilized, the presence or absence of a color killer signal is checked at the input port. If there is a color killer signal, the setting is determined to be correct and the setting state is maintained.
If there is no color killer signal, set system = NTSC and clock = 4.43 MHz (referred to as output mode 2)
To perform the same processing.

In output mode 2, if there is no color killer signal, system = NTSC, clock = 3.58 MHz
(Referred to as output mode 3) and the same processing is performed. If there is no color killer signal in any of the output modes 1, 2, and 3, the three processes are periodically repeated as shown in FIG.

By the way, the video chroma IC 2 constituting the circuit of the present invention is a PA having a vertical video frequency of 60 Hz.
When an L-type signal is input, there is a problem that a color killer signal is present in both output modes 1 and 2. Therefore, as shown in the flowchart of FIG. 2, the microcomputer 1 starts checking from the setting of the PAL system so that the signal of the PAL system having a vertical and horizontal frequency of 60 Hz is not held in the setting of NTSC 4.43.

The SECAM decoder IC3 is an NTSC
When a signal of the 3.58 system is input, the signal may be modulated and output to the PAL system. In this case, even in the output mode 1, there is a color killer signal.

When a video tape recorded in NTSC is played back by a PAL video tape recorder, a PAL signal having a vertical video frequency of 60 Hz is output. In mode 1, no color killer signal is output and output mode 2
The color killer signal comes out only in the case. That is, 60H
When the PAL signal of z is input by fast-forward reproduction, it is impossible to determine the PAL method. FIGS. 3 and 4 are flowcharts that solve the above problems in addition to the basic operation of FIG.

In FIGS. 3 and 4, F_PAL 60 is a flag that is set when the output mode is 1 and there is a color killer signal, and the color killer signal disappears from that state. This flag is reset when video mute is turned on by channel switching, screen switching, or the like. FIG. 3 shows the processing in the output mode 2 and 3, and FIG. 4 shows the processing in the output mode 1. In FIG. 3, first, the microcomputer 1 checks whether the video mute is on. On / off of the video mute is managed by an internal register of the microcomputer 1, and is turned on for a certain time (about 700 msec) when switching channels or screens.

If the video mute is on, F_PAL
Reset 60. Next, it is checked whether the vertical frequency of the input video signal is 50 Hz or 60 Hz. 50
At Hz, it is determined that only the PAL system or the SECAM system exists, and the output mode 1 is forcibly set.
At 60 Hz, different processing is performed in output modes 1, 2, and 3, respectively.

FIG. 4 shows the processing in the output mode 1. In output mode 2, check for the presence of a color killer signal,
If there is, output mode 2 remains, and if not, output mode 3
To finish the process. Also in the output mode 3, the presence or absence of a color killer signal is checked. If there is, the output mode 3 is maintained. The flowchart of FIG.
In this case, the presence or absence of a SECAM signal is first checked.
Since the SECAM method cannot be used, it is determined that an error has occurred, the next output mode 2 is set, and the process ends.

When there is no SECAM signal, the presence or absence of a color killer signal is checked. If not, check whether the video mute is on. If it is on, the next output mode 2 is set and the process is terminated. If not on, check F_PAL60.

When F_PAL 60 is "1", the output mode 3 is set and the process is terminated. If it is "0", it is checked whether or not there was a color killer signal in the previous output mode 1. If there is, F_PAL60 is set to “1”
To finish the process. If not, the next output mode 2 is set and the process ends.

As described above, the circuit of the present invention overcomes many circuit problems with the software of the microcomputer built in the television receiver, and realizes a system capable of judging the television system and automatically selecting the television system. are doing.

[0034]

In a television receiver capable of receiving multiple systems, a function of automatically selecting an optimum television system is indispensable to a user. However, as described at the beginning, a large number of circuits are required to determine the television system by a circuit. In the circuit of the present invention, since a microcomputer built in the television receiver is used, its function can be realized without adding a circuit in a system, and the effect is great. Also, as shown in the present embodiment, the algorithm of the microcomputer is simple, and its function can be realized with a ROM capacity of about 100 bytes. This means that it is not necessary to use a microcomputer having a large ROM capacity to add the functions of the present invention, and there is no need to consider increasing the cost of the microcomputer.

[Brief description of the drawings]

FIG. 1 is a block diagram of a color system determination circuit according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a basic algorithm of television system discrimination in FIG. 1;

FIG. 3 is a flowchart showing a detailed algorithm of television system discrimination in FIG. 1;

FIG. 4 is a flowchart showing a detailed algorithm of a television system discrimination in another mode in FIG. 1;

[Explanation of symbols]

 1 microcomputer 2 video chroma IC 3 SECAM decode IC

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 9/00 H04N 5/46

Claims (3)

(57) [Claims] 1. PAL system, SECAM system, NT
A receiving circuit for receiving four types of color television signals of an SC system and a modulated NTSC system in which a chroma signal is modulated to 4.43 MHz, and each television system circuit of the receiving circuit is disconnected.
Based on the information of the color killer voltage of the color demodulation circuit of the selected set method Te Rikae determine the presence or absence of color killer signals
Microcomputer that sets the switching of the TV system circuit of the received signal
When a PAL signal having a vertical video frequency of 60 Hz is input , the switching of the receiving circuit is set.
Chroma signal is 4.43 MH
Color killer even in modulated NTSC circuit modulated to z
In a system in which a signal is output and a color killer is determined , the microcomputer switches each television system circuit.
After a certain period of time, check if there is a color killer signal.
Check to see if the set method is correct
That time, the first to set the PAL system to check the color killer signal, then change the chroma signal of 4.43MHz
Set to the modulated NTSC system and the unmodulated NTSC system
Then, the color killer signal is sequentially checked, and the chroma signal is a modulated NTSC system of 4.43 MHz, an unmodulated NTSC system, or the chroma signal is a modulated NSC system of 4.43 MHz.
Check the TSC system to determine the TV system
Color system discriminating circuit, characterized in that the way. 2. A color system discriminating circuit according to claim 1, wherein said television system circuit of said receiving circuit is provided with said microcomputer.
Vertical video frequency is switched set to the PAL system by down 6
When it is receiving a signal of 0Hz of the PAL system, from the state of there color killer signal, the video tape of the fast-forward playback, etc.
When the state changes to a state without a color killer signal, the chroma signal is not switched to the 4.43 MHz modulated NTSC system after that, and only the two systems, the PAL system and the NTSC system, are checked. There the color system discriminating circuit, characterized in that to prevent the erroneous determination of the setting of the modulation NTSC system 4.43 MHz. 3. When a signal having a vertical video frequency of 60 Hz is input, the SECAM system is not determined.
2. The color system discrimination circuit according to claim 1, wherein