JPH08307796A - Confirmation signal identification circuit in television identification control signal - Google Patents

Abstract

PURPOSE: To provide the confirmation signal identification circuit in a television identification control signal which is capable of rightly identifying the confirmation signal in the identification control signal, regardless of the presence or absence of ghost. CONSTITUTION: The confirmation signals of the identification control signal in the television signal of an EDTV are inputted in a band-pass filter 1 and a low-pass filter 2. After the output of the band-pass filter 1 is demodulated by a demodulation circuit 6, the output is inputted in an operational amplifier 3. The output of the low-pass filter 2 is inputted in an operational amplifier 4. In the operational amplifier 4, the reference value detected by a reference value detection circuit 7 is inputted as threshold. An AND circuit 5 outputs a value of '1' as a detection result as a confirmation signal when the outputs of the operational amplifiers 3 and 4 are high or when the output of the band- pass filter 1 is larger than certain threshold (reference value) and the output of the low-pass filter 2 is smaller than the detected threshold.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a second-generation EDTV (hereinafter referred to as "the second-generation EDTV") which is compatible with the current NTSC color television transmission system and is transmitted in a letterbox format by providing a non-image part above and below a wide aspect image. , EDTV2), and a confirmation signal identification circuit for a confirmation signal in a television identification control signal transmitted.

[0002]

2. Description of the Related Art As a method for transmitting a high-definition wide aspect image while maintaining compatibility with the current NTSC color television transmission method, a non-image part is provided above and below the wide aspect image to form a letterbox format. The EDTV 2 that also transmits the reinforcement signal is being studied and is about to be put to practical use.

In this EDTV 2, in order to distinguish it from the current NTSC television signal, in other words, EDTV
1 to determine that it is a 2 television signal.
One horizontal scanning line period (22H and 285) for each field
H), the identification control signal is transmitted. This identification control signal is shown in FIG. As shown in FIG. 5, the identification control signal has a configuration in which one horizontal scanning line period is divided into 27 bits and signals of three different formats are superimposed. Bit position B3
˜B5 are NRZ format identification signals, B6 to B23 are carrier wave type identification signals with a frequency of fsc, and B25 to B27 are carrier wave type confirmation signals with a frequency of 4 fsc / 7. Here, fsc is the color subcarrier frequency (3.58M
Hz).

The identification control signal has a function of distinguishing a video signal from an identification control signal (confirmation function), a function of identifying a transmitted image, a kind of a reinforcement signal, a combination, a difference in processing, etc. (identification function). ), The receiver side has a function (control function) that serves as a phase reference for demodulating the reinforcement signal. Since the identification control signal is transmitted during the period in which the video signal is conventionally transmitted, bit positions B25 to B2 are used as a confirmation function in order to distinguish the video signal from the identification control signal.
A confirmation signal is transmitted to 7. In addition, the confirmation signal has the carrier wave form of 4 fsc / 7 and the direct current component 0 as described above,
The signal is impossible as an NTSC signal (see Japanese Patent Application No. 5-246588). Therefore, on the receiver side, it is necessary to extract this confirmation signal and accurately determine that it is an identification control signal.

FIG. 4 is a block diagram showing an example of a conventional confirmation signal identifying circuit, and a conventional confirmation signal discriminating method will be described using this. In FIG. 4, the confirmation signal of the identification control signal in the television signal of the EDTV 2 is 4
Band pass filter 1 for extracting the component of fsc / 7 = 2.04 MHz and low pass filter 2 for extracting the DC component
Is input to The output of the bandpass filter 1 is the demodulation circuit 6
After being demodulated by the operational amplifier 3, it is input to the non-inverting input terminal of the operational amplifier 3, and the output of the low-pass filter 2 is the operational amplifier 4
It is input to the inverting input terminal of. Since the reference value serving as the threshold value is input to the inverting input terminal of the operational amplifier 3 and the reference value serving as the threshold value is input to the non-inverting input terminal of the operational amplifier 4, the output of the operational amplifier 3 is the band pass filter 1.
Is high when the output is higher than the reference value, and the output of the operational amplifier 4 is high when the output of the low-pass filter 2 is lower than the reference value.

The outputs of the operational amplifiers 3 and 4 are input to the AND circuit 5, and the AND circuit 5 extracts the component of 4fsc / 7 = 2.04 MHz when the output of the operational amplifiers 3 and 4 is high, that is, the band pass filter 1 When the output of is larger than a certain threshold and the output of the low-pass filter 2 for extracting the DC component is smaller than the certain threshold, a value "1" is output as a detection result as a confirmation signal. In other cases, the value of "0" is output as the detection result because it is not the confirmation signal but the video signal. The method for discriminating the confirmation signal is also described in Japanese Patent Application No. 5-330518.

[0007]

In the conventional confirmation signal identification circuit shown in FIG. 4 described above, the reference value input to the non-inverting input terminal of the operational amplifier 4 is fixed, so that a blanking ghost during transmission or the like is generated. Due to the ghost interference that changes the DC component of, the DC component increases compared to the confirmation signal before transmission and exceeds the set threshold value, and the confirmation signal cannot be identified despite the confirmation signal. It was

The present invention has been made in view of the above problems, and provides a confirmation signal identifying circuit for a television identification control signal that can correctly identify the confirmation signal in the identification control signal regardless of the presence or absence of a ghost. The purpose is to do.

[0009]

In order to solve the above-mentioned problems of the prior art, the present invention transmits an identification control signal during a predetermined period of a television signal, and the identification control signal is included in this identification control signal. Is a confirmation signal identification circuit for identifying the confirmation signal in the television identification control signal transmitted including the confirmation signal for confirming that, by detecting the pedestal level in the vertical blanking period, In the respective fields, a detection unit that detects the signal level in the period of the confirmation signal,
When the confirmation signal frequency component in the period of the confirmation signal is equal to or higher than a certain threshold value and the DC component is less than or equal to the threshold value of the signal level detected by the detection means, it is a confirmation signal, otherwise the confirmation signal. The present invention provides a confirmation signal identifying circuit characterized by being provided with a confirmation signal detecting means for detecting that the confirmation signal is not.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A confirmation signal discriminating method and a confirmation signal discriminating circuit of a television discrimination control signal according to the present invention will be described below with reference to the accompanying drawings. 1 is a block diagram showing an embodiment of a confirmation signal identifying circuit for a television identification control signal of the present invention, and FIG. 2 is a waveform diagram for explaining the operation of the confirmation signal identifying circuit for a television identification control signal of the present invention. 3 is a circuit diagram showing an example of a specific configuration of the reference value detection circuit 7 in FIG. In FIG. 1, the same parts as those in FIG. 4 are designated by the same reference numerals.

In FIG. 1, the confirmation signal of the identification control signal in the television signal of the EDTV 2 is 4 fsc / 7 =
It is input to the band pass filter 1 for extracting the 2.04 MHz component and the low pass filter 2 for extracting the DC component. The output of the band pass filter 1 is demodulated by the demodulation circuit 6 and then input to the non-inverting input terminal of the operational amplifier 3, and the output of the low pass filter 2 is input to the inverting input terminal of the operational amplifier 4. A reference value serving as a threshold value is input to the inverting input terminal of the operational amplifier 3, and a reference value serving as a threshold value output from the reference value detection circuit 7 newly provided by the present invention is input to the non-inverting input terminal of the operational amplifier 4. , The output of the operational amplifier 3 becomes high when the output of the band pass filter 1 is larger than the reference value, and the output of the operational amplifier 4 becomes high when the output of the low pass filter 2 is smaller than the reference value.

The outputs of the operational amplifiers 3 and 4 are input to the AND circuit 5, and the AND circuit 5 extracts the component of 4fsc / 7 = 2.04 MHz when the output of the operational amplifiers 3 and 4 is high, that is, the band pass filter 1 When the output of is larger than a certain threshold and the output of the low-pass filter 2 for extracting the DC component is smaller than the certain threshold, a value "1" is output as a detection result as a confirmation signal. In other cases, the value of "0" is output as the detection result because it is not the confirmation signal but the video signal.

Now, consider the reference value detected by the reference value detection circuit 7 and input to the non-inverting input terminal of the operational amplifier 4. When the reference value is detected, there is a condition that there is no large temporal change, and this condition applies to a vertical blanking period or a horizontal blanking period other than the video period.
Moreover, as shown in FIG. 2, in the horizontal blanking period, the fluctuation of the DC component due to the ghost component does not always match the period of the confirmation signal. Therefore, when the direct current value during the horizontal blanking period decreases due to the ghost component as in Example 1 of FIG. 2, the reference value is set lower than usual, so the output of the operational amplifier 4 is unlikely to be high, and the confirmation signal is output. It becomes difficult to identify. Also,
When the DC value in the horizontal blanking period increases due to the ghost component as in Example 2 of FIG. 2, the reference value is set higher than usual, so that the output of the operational amplifier 4 is likely to be high, resulting in false detection in the video signal. Easier to do.

From the above, when a ghost disturbance is received, the period corresponding to the confirmation signal period of any one line in the vertical blanking period in which the direct current component similarly changes is optimum for detecting the reference value. Is. The confirmation signal is 4 fsc / 7.
Since the carrier type is 0 and the DC component is 0, the output of the low-pass filter 2 should be equal to the pedestal level in the case of the discrimination control signal. Therefore, it is understood that the pedestal level should be detected as the reference value.

The structure of the reference value detection circuit 7 for realizing this is shown in FIG. The reference value detection circuit 7 is a waveform acquisition circuit 7
1, a noise canceling circuit 72, and a level detecting circuit 73. The waveform acquisition circuit 71 acquires a signal for one line during the vertical blanking period. For example, 10H to 12
Since no signal is superimposed on H, the pedestal level can be easily detected. Also, 18H GC
Since the pedestal and the bar waveform of the R signal are repeated in an 8-field sequence, the pedestal level can be detected by capturing only the pedestal field.

The signal thus captured is input to the noise cancel circuit 72 to reduce noise. Then, the output of the noise cancel circuit 72 is input to the level detection circuit 73, and the signal level of the period corresponding to the period of the confirmation signal in the identification control signal is detected. The value detected by the level detection circuit 73 is used as a reference value for the operational amplifier 4
To enter. According to the present invention described above, the DC value in the confirmation signal period can be predicted by detecting the pedestal level in the vertical blanking period even if the DC value varies due to ghost interference, and an accurate threshold value is obtained. Can be set.

[0017]

As described in detail above, the confirmation signal identifying circuit in the television identifying control signal of the present invention is
Detection means for detecting the signal level in the period of the confirmation signal by detecting the pedestal level in the vertical blanking period, and in each field, the confirmation signal frequency component in the period of the confirmation signal is greater than or equal to a certain threshold, and the DC component Is a confirmation signal when the signal level detected by the detection means is a threshold value or less as the threshold value, and is provided with a confirmation signal detection means that detects a confirmation signal other than the threshold value at other times. The feature is that the confirmation signal in the identification control signal can be correctly identified regardless of the presence or absence.

[Brief description of drawings]

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

FIG. 2 is a waveform diagram for explaining the operation of the present invention.

FIG. 3 is a block diagram showing an example of a specific configuration of a reference value detection circuit 7 in FIG.

FIG. 4 is a block diagram showing a conventional example.

FIG. 5 is a waveform diagram showing an identification control signal in a television signal of EDTV2.

[Explanation of symbols]

 1 band pass filter 2 low pass filter 3,4 operational amplifier 5 AND circuit 6 demodulation circuit 7 reference value detection circuit (detection means)

Claims (1)

[Claims] 1. A television identification in which an identification control signal is transmitted in a predetermined period of a television signal, and the identification control signal includes a confirmation signal for confirming that the identification control signal is transmitted. A confirmation signal identification circuit for identifying a confirmation signal in the control signal, by detecting the pedestal level in the vertical blanking period, the detection means for detecting the signal level in the period of the confirmation signal, in each field, When the confirmation signal frequency component in the period of the confirmation signal is equal to or higher than a certain threshold value and the DC component is less than or equal to the threshold value of the signal level detected by the detection means, it is a confirmation signal, otherwise the confirmation signal. A confirmation signal identification circuit, characterized in that it is provided with a confirmation signal detection means for detecting that it is not.