JP2003209813A - Slicer for television signal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a slicer for a TV signal capable of obtaining a regular decode output at all times by revising a slice level and a slice timing depending on a state of a received signal in slicing a closed caption signal. <P>SOLUTION: The slicer is provided with: a closed caption signal extract section 1 for extracting the closed caption signal from the TV signal; a slicer section 2 for slicing the extracted closed caption signal at a slice level to form digital data; a decoder section 3 for decoding the obtained digital data; a signal strength discrimination section 7 for discriminating the strength of the received TV signal; a timing control section 5 for setting the slice timing of the slicer section 2; and a timing storage section 6 for storing the slice timing, and the timing control section 5 changes the slice timing of the slicer section 2 on the basis of a decode result by the decoder section 3 to obtain regular digital data from the slicer section 2. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television signal slicing device, and more particularly to an optimum slicer for a closed caption signal when decoding digital data obtained by slicing a closed caption signal superimposed on a television signal. The present invention relates to a slicing device for a television signal which is converted into digital data under certain conditions.

[0002]

2. Description of the Related Art In North America, a television receiver having a screen size of 13 inches or more displays a text display of narration, conversation, broadcast contents, etc. during broadcasting for a deaf listener. It has a function to display, and such a function is called a caption function.
In particular, since 1993, in order to achieve the caption function, it is stipulated in the United States that a television receiver has a built-in caption decoder, and television receivers having a caption function have become widespread. There is. An example of a television receiver having such a caption function is, for example, Japanese Patent Laid-Open No. 7-20339.
No. 6 is disclosed.

Also, recently, in the United States, it has become legal to add a function called V-CHIP to this caption function. This V-CH
The IP function is a degree of extremeness in the content of a television broadcast program, especially for a program having content that is not desirable for young people to listen to, for example, a program including content such as extreme violence scenes or sexual depictions. The caption decoder built in the television receiver excludes programs having a high ranking so that the television receiver does not display them.

In this case, the V-CHIP function uses the X in field 2 of the closed caption signal.
DS (Extended Data Service)
The data is used.

5A to 5D are waveform diagrams showing the structure of a television signal including a closed caption signal. FIG. 5A is a television signal (television composite signal), b) is the vertical sync signal,
(C) is a horizontal synchronizing signal, (d) is each waveform of a closed caption signal.

As shown in FIGS. 5 (a) to 5 (d),
The closed caption signal is superimposed on the television signal, and in the currently used television system, it is superimposed on the 21st horizontal synchronizing signal counted from the falling edge (e) of the vertical synchronizing signal. This closed caption signal is called field 1. In addition to this, another closed caption signal is also superimposed on the 284th horizontal synchronizing signal counted from the falling edge (e) of the vertical synchronizing signal (not shown). This closed caption signal is called field 2. The closed caption signal includes a burst signal of 3.58 MHz after the arrival of the horizontal synchronizing signal and a clock run-in (Clock) of 7 cycles following the burst signal.
Run-in) signal, a start bit (Start Bits) signal indicating the start of caption data following the clock run-in signal, and a 2-byte length closed caption data character (DataCharacters) following the start bit signal. And signals.

In the currently used television system, closed caption data is 2 bytes, and the most significant bit of each byte of the 2-byte data is used as a parity bit for detecting an error in the data. The so-called odd parity system is adopted as the television system currently used.

This odd parity system is "0" and "1".
In the data composed by and, "in each byte"
This is a method of setting so that the number of bits set to "1" is always an odd number. That is, if the number of bits set to "1" is an odd number, closed caption data (digital data) is normal. Judged as "1"
If the number of bits set to is even, it is determined that the closed caption data (digital data) is abnormal.

[0009]

In a television receiver having a known caption function, external noise is superimposed on the received closed caption signal when the electric field strength of the received signal is weak and the received signal level is low. Often. When external noise is superimposed on the closed caption signal, detection of the closed caption signal is affected by the external noise, and the slice level of the closed caption signal is prevented to prevent incorrect digital data from being output. Was trying to change. In addition, even if the electric field strength of the received signal is high and the received signal level is high, such as cable television, if the received signal is affected by an interference wave from an adjacent channel, In some cases, the closed caption signal is amplitude-modulated by the interfering wave, normal digital data cannot be obtained from the closed caption signal, and the digital data cannot be decoded. In such a case, it is considered that the closed caption signal is disturbed and it is impossible to extract the closed caption data based on the clock run-in signal.

Here, FIGS. 6A and 6B are waveform diagrams showing a closed caption signal that is not amplitude-modulated and a closed caption signal that is amplitude-modulated by an interfering wave. (A) is a closed caption signal which is not amplitude-modulated, and (b) is a closed caption signal which is amplitude-modulated.

As shown in FIG. 6 (a), when the closed caption signal which is not subjected to amplitude modulation is set to a slice level as shown by the alternate long and short dash line, at the first to fourth data sampling timings, respectively. 1,
Digital data of 0, 0, 1 is obtained, and 1001 regular data strings can be obtained as a whole.

On the other hand, as shown in FIG. 6 (b), when the closed caption signal amplitude-modulated by the interfering wave is set to the slice level as shown by the same dashed line as in the previous case, At the timing of extracting the data of 1, digital data which is not 1 but 0 is obtained, and an erroneous data string of 0001 is obtained as a whole. Therefore, the subtitle character string for the closed caption signal is garbled or a character blank is generated on the display screen of the television receiver, and the V-CHIP function is added to the caption function. , It becomes impossible to rank, or it becomes impossible to block programs that should block the display screen.

The present invention has been made in view of such a technical background, and an object thereof is to change a slice level and a slice timing according to a state of a received signal when slicing a closed caption signal. Thus, it is possible to provide a slicer for a television signal that can always obtain a normal decoded output.

[0014]

In order to achieve the above object, the present invention provides a closed caption signal extracting section for extracting a closed caption signal from a television signal on which a closed caption signal is superimposed, and a closed caption signal extracting section. Slicing the closed caption signal extracted in step 1 at a predetermined slice level, and a slicer section for forming digital data, and a decoder section for decoding the digital data formed by the slicer section,
A signal strength judgment unit that judges the received signal strength of the received television signal and outputs the judgment result, a timing control unit that sets the slice timing when slicing the closed caption signal with the slicer unit, and a timing control unit And a timing storage unit that stores the slice timing, and the timing control unit changes the slice level of the slicer unit based on the determination result of the signal strength determination unit so that normal digital data can be obtained from the slicer unit. And a means for changing the slice timing of the slicer section based on the decoding result of the decoder section.

According to the above means, the timing control section is
In order to obtain regular digital data from the slicer unit, the timing control unit not only changes the slice level of the slicer unit based on the determination result of the signal strength determination unit but also changes the slicer unit based on the decoding result of the decoder unit. The control is performed so that the slice timing of the closed caption signal is changed. The closed caption signal is affected by a strong interfering wave, and the amplitude modulation signal is superimposed on the closed caption signal so that the positive and negative levels of the binary data are cycled. Even if the positive level of the binary data exceeds the slice level at any slice timing position of the closed caption signal, the slice timing is set to the positive level of the binary data. If you change to the part that exceeds the level, it is a regular digital It is possible to obtain the over data.

In this case, the slice timing is changed by the timing controller in the above means when normal digital data is not output from the slicer.
Until the regular digital data is output, the slice timing is shifted from the initial slice timing position within the specified range in one direction or the other direction by unit position.

With such a structure, the slice timing position can be set extremely finely, and the portion where the positive level of the binary data in the closed caption signal exceeds the slice level is detected without leaking and the normal digital signal is detected. You can get the data.

Further, the slice timing is changed by the timing control section in the above-mentioned structure. First, the slice timing is shifted from the initial slice timing position to a unit position in one direction within the specified range, and then the slice timing is changed to the initial stage. The unit shifts from the slice timing position in the specified range to the other direction by unit position.

With such a configuration, the slice timing can be reliably set to any of the slice timing positions within the specified range, and the positive level of the binary data in the closed caption signal is the slice level. Regular digital data can be obtained by detecting the excess portion without leaking.

Further, in the above-mentioned means, the change of the slice timing performed by the timing control section is to shift to the initial slice timing position when the supply of the clock run-in signal is not confirmed.

With such a configuration, it is not necessary for the timing control unit to move the slice timing position after the slice timing has been moved to the initial slice timing position in the timing control unit. Can be reduced.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an essential configuration of an embodiment of a television signal slicing device according to the present invention.

As shown in FIG. 1, the television signal slicing apparatus according to this embodiment includes a closed caption signal extraction section 1, a slicer section 2, a decoder section 3, and a digital data correctness determination section 4. , Timing control unit 5, timing storage unit 6, and signal strength determination unit 7
And a television signal input terminal 8 and a television reception signal input terminal 9.

The closed caption signal extraction unit 1 has its input end connected to the television signal input terminal 8 and its output end connected to the input end of the slicer unit 2. The output end of the slicer unit 2 is connected to the input end of the decoder unit 3, and the control end thereof is connected to the control end of the timing control unit 5. The decoder unit 3 has an output end connected to an input end of the digital data correctness determination unit 4 and has a digital data correctness determination unit 4
Has an output end connected to a first input end of the timing control unit 5. The timing control unit 5 has a second input end connected to the output end of the signal strength determination unit 7, and also connected to the timing storage unit 6. The input end of the signal strength determination unit 7 is connected to the television reception signal input terminal 9.

In this case, the closed caption signal extraction unit 1 extracts the closed caption signal from the television signal supplied to the television signal input terminal 8 and supplies the extracted closed caption signal to the slicer unit 2. This closed caption signal is
It is superimposed on the 21st or 284th horizontal synchronizing signal of the television signal. The slicer unit 2 slices the closed caption signal supplied from the closed caption signal extraction unit 1 at a predetermined slice level,
The slice signal is output as binary digital data.
The decoder unit 3 analyzes the binary digital data supplied from the slicer unit 2, and displays the analysis result as characters on the display screen of the television receiver.

The digital data correctness determination unit 4 determines whether the closed caption signal is superposed from the decoder output of the decoder unit 3, that is, whether the closed caption signal is present, and at the same time, the binary digital data is correct. Or not. In this case, the correctness of the binary digital data is determined by checking the presence or absence of the start bit 001 (see FIG. 5D) in the closed caption signal and performing a parity check of the digital data. That is, start bit 0
If 01 is present and the 2-byte digital data satisfies the odd parity, it is determined that there is a closed caption signal. On the other hand, if the start bit 001 does not exist or the 2-byte digital data does not satisfy the odd parity, it is determined that there is no closed caption signal. At present, the correctness determination of the digital data is more reliable, but as another method, there is also a method of determining only the presence or absence of the start bit. Also, in order to match the current method, the start bit is 001, and an example using odd parity has been described, but the start bit is 0.
10 may be used, or even parity may be used.

The timing control unit 5 sets the slice level of the slicer unit 2 to a level based on the determination result of the signal strength determination unit 7, and closes the slice level at the slice timing based on the determination result of the digital data correctness determination unit 4. Slice the caption signal. At this time, when slicing the closed caption signal in the slicer unit 4, the timing control unit 5 first slices the closed caption signal at the initial slice timing (standard slice timing).
In this state, if the signal strength judgment unit 7 judges that the signal strength is high, the digital data correctness judgment unit 4 judges that there is a closed caption signal, and the digital data is not legitimate (undefined character), it is closed. It is determined that the caption signal is amplitude-modulated, the slice timing is changed in small steps until the digital data becomes regular, and the slice timing when the digital data becomes regular becomes the timing storage unit 6. Remember. This slice timing is stored for each channel.

The signal strength judgment unit 7 judges the reception strength of the television reception signal (high frequency signal) supplied to the television reception signal input terminal 9 and determines the signal strength representing the signal strength. Supply to 5.

Next, FIGS. 2 and 3 are flow charts showing the operation history when changing the slice timing performed by the television signal slicing apparatus shown in FIG. 1, and FIG. 2 shows the operation history. 3 is the latter half of the operation history.

The process of changing the slice timing will be described with reference to FIGS.

First, in step S1, the timing control section 5 first reads the slice timing stored in the timing storage section 6 (the initial slice timing is read at the initial stage), and the read slice timing is sliced by the slicer section 2. Transfer settings to.

Next, in step S2, the timing control section 5 reads the reception strength of the television reception signal judged by the signal strength judgment section 7, and transfers and sets the slice level corresponding to the reception strength to the slicer section 2. In addition,
The means to set the slice level corresponding to the reception intensity is
Since this is a commonly used means in this kind of field, description of means for setting the slice level is omitted here.

Next, in step S3, the slicer unit 2 slices the supplied closed caption signal at the set slice level and slice timing, and outputs the slice signal as binary digital data.

In step S4, the timing control section 5 determines whether or not the digital data correct / incorrect determination section 4 has a clock run-in signal. And
When it is determined that the clock run-in signal is present (Y), the process proceeds to the next step S6, while the clock run-in signal is output.
If it is determined that there is no IN signal (N), another step S
Go to 5.

Subsequently, in step S5, the timing control unit 5 returns the slice timing to the initial slice timing because there is no closed caption signal, and ends this series of flowcharts.

Further, in step S6, the timing control section 5 determines whether or not the digital data correctness determination section 4 has regular digital data. When it is determined that there is regular digital data (Y), the process proceeds to the next step S7, while when it is determined that there is no regular digital data (N), the process proceeds to another step S8.

Next, in step S7, the decoder section 3 decodes the regular digital data when the timing control section 5 determines that there is regular digital data. When the decoding is completed, this series of flowcharts is completed.

Next, in step S8, the timing control section 5 judges from the judgment result of the signal strength judgment section 7 whether or not the television signal reception level is strong. When it is determined that the television signal reception level is strong (Y), the process proceeds to the next step S10, while when it is determined that the television signal reception level is not strong (N), the process proceeds to another step S9. .

In the subsequent step S9, the timing control section 5 may malfunction such as erroneous detection when slicing the closed caption signal because the television signal reception level is not strong. Therefore, the slice level of the slicer section 2 malfunctions. Change to a level that does not. It should be noted that, as described above, the change of the slice level is a means which is usually carried out in this kind of field, and therefore the explanation of the means for setting the slice level is omitted.

Then, in step S10, the timing control section 5 slices the closed caption signal by amplitude-modulating the binary level of the closed caption signal due to the influence of the interfering wave although the television signal reception level is strong. Occasionally, an erroneous operation such as an erroneous detection may occur. Therefore, the slice timing position of the closed caption signal performed by the slicer unit 2 is shifted from the initial slice timing position in a direction (one direction) in which time advances by a unit timing position (+1).

Next, in step S11, the slicer unit 2 slices the supplied closed caption signal at the set slice level and slice timing, and outputs the slice signal as binary digital data.

Next, in step S12, the timing control section 5 determines whether or not there is a clock run-in signal by the digital data correctness determination section 4. Then, it is determined that there is a clock run-in signal (Y).
If so, the process proceeds to the next step S14, while the clock
If it is determined that there is no run-in signal (N), the process proceeds to another step S13.

In the subsequent step S13, the timing control section 5 returns the slice timing to the initial slice timing because there is no closed caption signal, and ends this series of flowcharts.

Subsequently, in step S14, the timing control section 5 determines whether or not there is normal digital data by the digital data correctness determination section 4. And
If it is determined that there is regular digital data (Y), the process proceeds to the next step S15, while if it is determined that there is no regular digital data (N), the process proceeds to another step S17.

Next, in step S15, the timing control section 5 stores the slice timing of the closed caption signal in the slicer section 2 set at this time in the timing storage section 6.

Next, in step S16, the decoder section 3 decodes the regular digital data because the timing control section 5 determines that the regular digital data is present. When the decoding is completed, this series of flowcharts is ended.

In step S17, the timing control section 5 determines that the slice timing position of the closed caption signal performed by the slicer section 2 is in the direction (one direction) in which time advances from the initial slice timing position by the unit timing position (+1). By shifting, it is determined whether or not the slice timing position has reached the maximum position within the specified range. Then, when it is determined that the slice timing position has already reached the maximum position within the specified range (Y), the process proceeds to the next step S19, while it is determined that the slice timing position has not yet reached the maximum position within the specified range ( If N), the process proceeds to another step S18.

Subsequently, in step S18, the timing control section 5 advances the slice timing position of the closed caption signal performed by the slicer section 2 by a unit timing position (+1) from the previous slice timing position (one direction). Direction). When this process ends, the process returns to the previous step S11, and the operations after step S11 are repeated and executed again.

Next, in step S19, the timing control section 5 returns the slice timing to the initial slice timing because the slice timing position has already reached the maximum position within the specified range.

Next, in step S20, the timing control unit 5 delays the slice timing position of the closed caption signal performed by the slicer unit 2 by a unit timing position (-1) from the initial slice timing position (the other direction). ).

Next, in step S21, the slicer unit 2 slices the supplied closed caption signal at the set slice level and slice timing, and outputs the slice signal as binary digital data.

In the following step S22, the timing control section 5 determines whether or not there is a clock run-in signal by the digital data correctness determination section 4. Then, it is determined that there is a clock run-in signal (Y).
If so, the process proceeds to the next step S24, while the clock
When it is determined that there is no run-in signal (N), the process proceeds to another step S23.

Then, in step S23, since there is no closed caption signal, the timing control section 5 returns the slice timing to the initial slice timing and ends this series of flowcharts.

Next, in step S24, the timing control section 5 determines whether or not there is normal digital data by the digital data correctness determination section 4. When it is determined that there is regular digital data (Y), the process proceeds to the next step S25, while when it is determined that there is no regular digital data (N), the process proceeds to another step S27.

Next, in step S25, the timing control section 5 stores the slice timing of the closed caption signal in the slicer section 2 set at this time in the timing storage section 6.

In step S26, the decoder section 3 decodes the regular digital data because the timing control section 5 determines that the regular digital data is present. When the decoding is completed, this series of flowcharts is completed.

Then, in step S27, the slice timing position of the closed caption signal performed by the slicer unit 2 shifts from the initial slice timing position in the direction delayed by the unit timing position (-1) (the other direction). , It is determined whether or not the slice timing position has reached the minimum position within the specified range. When it is determined that the slice timing position has already reached the minimum position within the specified range (Y), the next step S29.
On the other hand, when it is determined that the slice timing position has not yet reached the minimum position within the specified range (N), the process proceeds to another step S28.

Next, in step S28, the timing control unit 5 further changes the slice timing position of the closed caption signal performed by the slicer unit 2 from the previous slice timing position to the unit timing position (-
1) Shift to the direction in which the time is delayed (the other direction).
When this process ends, the process returns to the previous step S21,
Again, the operations after step S21 are repeatedly executed.

Next, in step S29, the timing control section 5 returns the slice timing to the initial slice timing because the slice timing position has already reached the minimum position within the specified range. When this process ends, this series of flowcharts ends.

FIG. 4 is a waveform diagram showing the slicing operation of the closed caption signal performed by the television signal slicing device shown in FIG.

The closed caption signal waveform in FIG. 4 corresponds exactly to the closed caption signal waveform shown in FIG. 6 (b).

As shown in FIG. 4, the known television signal slicing device fixedly sets the slice timing of the closed caption signal to the slice timing position Ts. Therefore, at the slice timing position Ts, the amplitude modulation is performed. When the positive level of the stored binary data does not exceed the slice level, the detection result of the digital data at the slice timing position Ts is 0, and incorrect digital data is detected.

On the other hand, in the television signal slicing device according to this embodiment, the slice timing of the closed caption signal is sliced from the slice timing position Ts up to that point when the positive level of the binary data amplitude-modulated is sliced. Since the transition is made to the slice timing Ts ′ having a portion exceeding the level, the detection result of the digital data at the slice timing position Ts ′ becomes 1, and normal digital data can be detected.

[0065]

As described above, according to the invention as set forth in claim 1, the timing control unit determines in the signal strength determination unit in the timing control unit that the regular digital data can be obtained from the slicer unit. Not only is the slice level of the slicer section changed based on the result, but the slice timing of the slicer section is also changed based on the decoding result of the decoder section. Affected by
Even if the amplitude modulation signal is superimposed on the closed caption signal and the positive / negative level of the binary data fluctuates periodically, at any slice timing position of the closed caption signal, the positive level of the binary data becomes the slice level. Since there is a portion that exceeds the slice level, by changing the slice timing to a portion where the positive level of the binary data exceeds the slice level, it is possible to obtain normal digital data.

Further, according to the invention described in claim 2, the slice timing position can be set extremely finely, and the portion where the positive level of the binary data in the closed caption signal exceeds the slice level is detected without leaking. Then, there is an effect that regular digital data can be obtained.

Further, according to the invention of claim 3,
The slice timing can be surely set to any of the slice timing positions within the specified range, and the portion where the positive level of the binary data in the closed caption signal exceeds the slice level is detected and the normal value is detected. The effect is that digital data can be obtained.

In addition to this, according to the invention as set forth in claim 4, since it is not necessary for the timing control section to shift the slice timing position after shifting the slice timing to the initial slice timing position in the timing control section, There is an effect that the operation load of the timing control unit can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an essential configuration of an embodiment of a television signal slicing device according to the present invention.

FIG. 2 is a flowchart showing a first half of an operation history when changing a slice timing performed by the television signal slicing apparatus shown in FIG.

FIG. 3 is a flowchart showing a latter half of the operation history when changing the slice timing performed by the television signal slicing device shown in FIG. 1.

FIG. 4 is a waveform diagram showing a slicing operation of a closed caption signal performed by the television signal slicing device shown in FIG. 1.

FIG. 5 is a waveform diagram showing a configuration of a television signal including a closed caption signal.

FIG. 6 is a waveform diagram showing a closed caption signal that is not amplitude-modulated and a closed caption signal that is amplitude-modulated by an interfering wave.

[Explanation of symbols]

1 Closed caption signal extraction section 2 slicer section 3 decoder 4 Digital data correctness judgment section 5 Timing controller 6 Timing storage 7 Signal strength judgment unit 8 Television signal input terminal 9 Television reception signal input terminal

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Claims (4)

[Claims] 1. A closed caption signal extraction unit that extracts a closed caption signal from a television signal on which a closed caption signal is superimposed, and a closed caption signal extracted by the closed caption signal extraction unit is sliced at a predetermined slice level,
A slicer unit that forms digital data, a decoder unit that decodes the digital data formed by the slicer unit, a signal strength determination unit that determines the reception signal strength of the received television signal and outputs a determination result, and the slicer A timing control unit that sets a slice timing when slicing the closed caption signal in a unit, and a timing storage unit that stores the slice timing set in the timing control unit, and the timing control unit is from the slicer unit. The slice level of the slicer unit is changed based on the determination result of the signal strength determination unit and the slice timing of the slicer unit is changed based on the decoding result of the decoder unit so that normal digital data is obtained. Tele characterized by Slice apparatus of the television signal. 2. When the slice timing is changed from the initial slice timing position, the slice timing is changed until the normal digital data is output when the normal digital data is not output from the slicer unit. The television signal slicing device according to claim 1, wherein the slicing device for television signals is performed by shifting the defined range in one direction or the other direction by unit position. 3. The slice timing is changed by the timing control unit by first shifting the slice timing from the initial slice timing position to a unit position in one direction within a prescribed range, and then changing the slice timing to the initial slice timing. The slicing device for a television signal according to claim 2, wherein the slicing device shifts from the position within the specified range to the other direction by unit position. 4. The television according to claim 1, wherein the change of the slice timing performed by the timing control unit is to shift to the initial slice timing position when the supply of the clock run-in signal is not confirmed. John signal slicer.