JP3080707B2 - Television 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 television system discriminating circuit suitable for use in a SECAM television receiver, which discriminates whether a received signal is a color broadcast or a black and white broadcast.

[0002]

2. Description of the Related Art SECAM color broadcasting is carried out in Eastern Europe and the Middle and Near East. A color identification signal called an ID (identity) signal of the SECAM broadcast is inserted at two places of a line (H) and a field (V), and is composed of different signals. In the SECAM system, color difference signals are transmitted line-sequentially, so that an ID signal carries an unmodulated carrier in a line and a carrier with the maximum frequency shift in a field so that not only color identification but also line-sequential color difference can be identified. ing.

In a SECAM color television, it is necessary to extract the polarity of a line-sequential color difference signal and color / monochrome discrimination information from the ID signal. FIG. 4 shows a conventional system identification circuit.

An ID signal separated from an input chroma signal is supplied to an input terminal 1 and input to an ID demodulation circuit 2.
In the ID demodulation circuit 2, fB−Y = 4.25 MHz , fR−
The ID signal of Y = 4.406MH z to FM demodulation to obtain the different alternating waves of DC voltage for each line. The demodulated signal is input to the level detection circuit 3, and the pulse generated based on the horizontal frequency HP input to the terminal 1 is input. The demodulated signal is alternately changed by a line switch pulse from the output of the flip-flop (FF) 10. Integrate with the capacitor 4. If the polarities of both input signals match, the switch polarity of the FF 10 is correct, and the voltage of the capacitor 4 increases. Conversely, when the polarity is inverted, it is necessary to correct the switch polarity of the FF 10, so that the level detection circuit 3 outputs an error detection signal to the FF 10. The capacitance voltage is compared and detected with a predetermined comparison voltage, and when it is detected that the color is sufficient,
The color detection signal is output to the ID determination circuit 5. The level detection circuit 3 supplies H.ID and V.I supplied to the terminals 6 and 7.
It is activated by the D key pulse. The other periods are cut off to avoid detection of unnecessary signals.

In the ID discriminating circuit 5, if the color detection signal is 1
Detect if the field is continuous. The terminal 9 ID determination Priority determination circuit 5 for taking out a discrimination output, is 1 when field continuous, output DC voltage that indicates a color state and the non or no color signal continuously is not, the DC potential indicating the killer state Output. By the discrimination output, the path of the color difference demodulation system is turned ON / OFF, and unnecessary color difference signals can be prevented from appearing on the screen in the killer state.

[0006] in FIG. 5 (a) shows the composite signal to be input, V · waveform of 10 to 15 V · ID signal line after this one vertical synchronizing signal, and input to the pin 7 (b) This is extracted by an ID key pulse. In the conventional ID-size constant circuit 5, the level detection result by V · ID detection is delayed one field, the efficiency is poor. The trigger point of the ID signal determination is the rising of the trigger pulse VCK1 shown in FIG.
The determination is made in the next field without determining the result of the level detection of the ID signal.

In an area where the SECAM system is used, H
-There is an experimental result that in some countries, the quality of the ID signal is extremely poor, and in that area, it is best to determine the ID signal using only the V-ID. In these areas, both H and V IDs
When the key is turned on and received, the capacitance voltage detected in the field is discharged at the time of line ID demodulation, and drops to a black and white potential at the timing of the trigger pulse VCK1.

Further, even if only the field ID is turned on, since the next field is to be determined, the charge / discharge information is damaged due to discharge due to leakage of the charge charged in the capacitor 4 or the like.

[0009]

When the above-mentioned situation occurs, the screen will end up with a color fading or a screen in which the coloration and the color fading are repeated, resulting in a loss of image quality.

According to the present invention, there is provided an SE that does not require color adjustment and does not need to be adjusted by the destination of the set manufacturing and user adjustment.
An object of the present invention is to provide a CAM system discriminating circuit.

[0011]

According to the present invention, the position of the trigger pulse applied to the ID determination circuit is changed, and the ID determination circuit is driven by a pulse having a trigger near the trailing edge of the V.ID key pulse.

[0012]

According to the above means, the result of demodulating the ID signal at the trailing edge of the V.ID key pulse is detected as a level.
・ ID detection result is output. If the ID signal is determined at this timing, the immediately preceding detection result can be used, so that the ID signal can be used without being affected by leakage or H · ID discharge.
A signal determination can be made.

[0013]

FIG. 1 shows an embodiment of the present invention, and the same parts as those in FIG. 4 are denoted by the same reference numerals.

Only the ID signal is separated from the SECAM chroma signal, supplied to the ID signal input terminal 1, and input to the ID demodulation circuit 2. The demodulated output of the ID demodulation circuit 2 is input to the level detection circuit 3, and the polarity is inverted by the line switch pulse from the FF 10 driven based on the horizontal pulse supplied to the terminal 11 to charge and discharge the capacitor 4. When the potential of the capacitor 4 is low, the level detection circuit 3 determines that the switch polarity of the FF 10 is inverted as in the related art,
An error signal is output to FF10 so that the inverted phase of F10 is correct.

When the potential of the capacitor 4 is sufficiently high, a color detection signal is output to the ID determination circuit 5. Both the H and V.ID key pulses supplied to the terminals 6 and 7, respectively, are input to the level detection circuit 3 to control and select the timing for activating the level detection circuit 3.

The ID determination circuit 5 detects the continuity of the color detection signal using the trigger pulse VCK2 input to the terminal 13. The ID determination circuit 5 determines that the color detection signal is black and white when the color detection signal disappears or does not exist at all during one field period, and outputs a voltage indicating a killer state. As in the prior art, the chroma path of the color difference demodulation system is cut off by the state of the color / killer to prevent the color difference demodulated signal from appearing on the screen when the killer is on.

The operation of FIG. 1 will be described in further detail using the waveforms of FIG. (A) shows a composite signal to be input. Of these signals, V · ID signals of 10 to 15 lines after the vertical synchronization signal are converted to V · I of waveform (b).
Extracted by D key pulse. 7 to 7 in the ID demodulation circuit 2
Either demodulation of the V / ID signal of 15 lines or demodulation of the V / ID signal of 10 to 15 lines may be used. V
The level detection by the ID key pulse is limited to 10 to 15 lines.

As described above, the line ID of the input ID signal
If the quality is poor and discharge occurs when the level is detected by the H.ID key, the voltage waveform of the capacitor 4 is (d).
become that way. The voltage that had dropped to the black and white level,
As shown in (b), the voltage rises during the V.ID period and exceeds the threshold voltage for color level detection. Then, the output of the level detection circuit 3 becomes as shown in a waveform (e). When this is determined by the trigger pulse VCK2 shown in the waveform (c), it can be determined that the color is at the rising edge of the trigger pulse VCK2. In this case, it is not continuous within one field,
Colors and becomes only V · ID period, the discrimination output of the ID determination circuit 5 becomes the killer state, means for determining which color is proposed by Unamono are shown in Japanese Patent Application No. Hei 1-308309 If this means is used, the V / ID color detection result can be used effectively.

When only the field ID in which the H.ID key is off is detected, the trigger pulse VC is detected immediately after the detection period.
Since K2 triggers, there is no influence of detection voltage deterioration due to leakage. As described above, the timing of the trigger pulse VCK2 is changed in order to utilize the detection result by the V · ID key, so that the trigger position of the trigger pulse VCK2 is VI · I.
The effect of the present invention is not impaired if it is behind the leading edge of the D key.

FIG. 3 shows another embodiment of the present invention applied to a multi-color television receiver capable of receiving two or more types including the SECAM system. In this embodiment, in addition to the SECAM system reception, PAL, NTS
It is intended for those capable of receiving all signals of the C system.

The ID judging circuits 5 and 1 correspond to the outputs of the level detecting circuits of each system of SECAM, PAL and NTSC.
2 and 14, respectively. Here, a trigger pulse VCK2 is input to each of the ID discriminating circuits 5, 12, and 14, and is given as a trigger clock. Since the PAL and NTSC systems do not include a field ID signal as in the SECAM system, there is no problem even if a clock is present at any timing within the vertical blanking period. Since each ID signal is operated at the same timing, the timing of the output of the ID discrimination circuit is output at the same time, and there is no fear that the next stage of the system logic 23 will cause erroneous discrimination or a time lag of discrimination.
The system logic 23 outputs the result of the determination as a control output of each unit, and switches the color subcarriers of PAL and NTSC.
Switching of a color difference demodulation path, switching of a color difference matrix, and the like are performed.

Various means can be considered for generating the trigger pulse VCK2 used in the present invention. For example,
V blanking pulse, H blanking pulse and gate pulse are input in the form of a sandcastle, the delay time from the leading edge of V is counted internally, and VCK2 is generated at the timing when a certain count value is reached. Can be If there is a synchronization signal in the same chip, a pulse obtained by counting down from the output of the V synchronization separation circuit may be used as a trigger pulse.

[0023]

As described above, according to the television system discriminating circuit of the present invention, it is not necessary to cope with the directional location of the set manufacture and to make user adjustments, so that color erasure hardly occurs.
An ECAM system determination circuit can be provided.

[Brief description of the drawings]

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

FIG. 2 is a timing chart for explaining the operation of FIG. 1;

FIG. 3 is a system diagram showing another embodiment of the present invention.

FIG. 4 is a system diagram showing a conventional discrimination circuit.

FIG. 5 is a timing chart for explaining the operation of FIG. 4;

[Explanation of symbols]

 2 ID demodulation circuit 3 Level detection circuit 4 Capacitor 10 FF 11 Gate generation circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H04N 9/00 H04N 9/70 H04N 5/46

Claims (2)

(57) [Claims] Pulses have to detect full I <br/> Rudokara identification signal 1. A SECAM system television signal
A determining circuit using at least the received signal period information a color or black and white, and a detection circuit for detecting the continuity of the output of this determine Teikairo, pulses for detecting the field color identification signal
Of received signal using period information
Te, before Killen a connection of the detection, the television system judgment circuit and performing using field synchronizing pulses before beginning <br/> or Ru behind the edge of the pulse. 2. The method according to claim 1, wherein said field period pulse is SECA.
2. The television system discriminating circuit according to claim 1, wherein the circuit is also used for detecting continuity of television systems other than M.