JPH01162494A - Method and its related device for recording and reproducing image signal containing teletext signal - Google Patents

Abstract

PURPOSE:To accurately decode teletext signal data by separating a pilot signal at the time of reproduction and making a necessary clock signal. CONSTITUTION:At the time of decoding the teletext signal, the clock signal used at a character signal extracting part is recorded as a pilot signal in recording an image signal superimposed by a teletext signal. In reproducing, a horizontal synchronizing signal is separated at a horizontal synchronizing separation circuit 68 from a reproducing composite signal obtained from a mixer 66, a pilot signal is extracted and outputted from a clock output terminal 92. The clock signal is 1/2-divided by a 1/2-divided 86, adjusted to coincide with the level and phase of the pilot signal, given to a subtractor 70 only during the period of the horizontal synchronizing signal and the pilot signa superimposed in recording is removed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a video signal recording/reproducing device or its external equipment, and in particular, to a video signal recording/reproducing device or an external device for recording/reproducing a signal in which a teletext signal is superimposed on a vertical retrace period of a video signal. The present invention relates to a video signal recording/reproducing device or its external equipment.

[Prior Art] A signal in which a teletext signal is superimposed on the vertical retrace period of a video signal is received from the broadcast and recorded in a video recording and reproducing device, and then a clock is used to decode the character signal when reproducing the received signal. A signal is required.

In the conventional method, a color burst signal is extracted from the reproduced video signal, and the above-mentioned clock signal is generated based on this color burst signal. FIG. 4 is a block diagram showing a data extraction section of a conventional character signal decoder. In Fig. 4, the video signal with the character signal superimposed is B
It is applied to the burst gate 102 via the P F 100, and also to the synchronization separation circuit 120 and the AGC/data slice circuit 122. Synchronous separation circuit 120
The horizontal synchronization signal separated by is applied to the burst gate 102 as its gate timing signal via the delay line 124, and therefore a color burst signal of about 3.58 MHz is extracted and applied to the first PLL circuit 104. This first PLL circuit 104 is 3.58M1lz
V X 010B and a phase comparator 108,
V X O10B to lock to color burst signal
oscillates. The output of VXOlO[1 is approximately 5.72MHz
VXO 112, counters 114, 11[1, and phase comparator 118.

In other words, V X O1 of 5.73 M1lz, so as to lock to the oscillation signal of V
12 performs the oscillation operation, and this V
The output signal is used as a clock signal used when extracting character signals.

In FIG. 4, 126 is a vertical synchronization separation circuit, and 128 is an O
Read signal generation circuit consisting of R gate and monomulti, 1
30 is a shift register, 132 is a fuse ROM, 13
4 is a frame pulse flywheel circuit, 13B is an error correction LSI, 138 is a buffer memory, 140 is a delay line, and 142 is a sub CPU. Second PLL
The clock signal from circuit 110 is connected to delay line 140.
However, in order to extract the character data in the best condition, it is sent to the delay line 140 by the sub CPU 142.
4 - Control the delay time. That is, the sub CPU 142 forcibly changes the delay time and uses the resulting delayed clock signal to find the delay time that minimizes the error in the error correction LSI 136.

[Problems to be Solved by the Invention] In the above-mentioned conventional system, it is difficult to decode a character signal that is once recorded on a video signal recording/reproducing device such as a video tape recorder and then reproduced. This is due to the following reason. In the low frequency conversion color (color under) method, during playback, the color burst is frequency converted to 3.58MHz with jitter compensated, but the signal that has passed through the luminance signal system still has jitter. Because of this, there is a phase shift from the color burst. In the conventional method described above, the clock signal used to extract the character signal is created based on the color burst, but since the reproduced character information fluctuates over time following jitter,
The optimal tarok phase will be completely different for each field. However, the phase adjustment using the delay line does not have a responsiveness that is fast enough to adjust the phase within the clock run-in time range of about 8 bits of each data packet. Therefore, the phases cannot be adjusted sufficiently and the optimal clock phase differs for each field, so the framing code cannot be accurately recognized and it is assumed that the teletext signal is not included.

[Means and effects for solving the problems] An object of the present invention is to solve the above problems and provide a method for accurately decoding a teletext signal that has been recorded and then played back. It is something.

In the present invention, unlike the conventional method, the clock signal used when decoding the teletext signal is generated in advance when recording the video signal, and is recorded as a pilot signal together with the video signal. It is designed to generate a lock signal.

That is, according to the present invention, when a video signal recording device records a signal in which a teletext signal is superimposed on a vertical blanking period of a video signal, a color burst signal of the video signal is used to record a pilot signal of a predetermined frequency. After the pilot signal is superimposed on the horizontal synchronizing signal section of the luminance signal separated from the video signal, the luminance signal is mixed with the color signal separated from the video signal and recorded. The pilot signal is extracted from the horizontal synchronizing signal in the video signal reproduced by the video signal reproducing device, a clock signal of a predetermined frequency is generated based on the pilot signal, and the clock signal of a predetermined frequency is generated from the reproduced video signal based on the clock signal. A method for recording and reproducing a video signal including a teletext signal in which a teletext signal is extracted is provided, and also includes means for separating a luminance signal and a color signal from an input video signal to be provided to a video recording device, and means for separating a synchronization signal; and means for extracting a color burst signal in response to the color signal;
There is provided an apparatus comprising means for generating a pilot signal of a predetermined frequency using the color burst signal, and means for superimposing the pilot signal on the luminance signal in response to the horizontal synchronization signal, further comprising a video reproducing apparatus. means for separating a horizontal synchronization signal from a video signal reproduced from the video signal; and means for generating a clock signal of a predetermined frequency using a signal superimposed on a horizontal synchronization section of the video signal in response to the horizontal synchronization signal. A device will be provided.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a recording system of an apparatus for realizing the recording and reproducing method of a video signal including a teletext signal according to the present invention. The entire recording system shown in FIG. 1 may be incorporated into a video recording device such as a VTR, or only the portion indicated by the dotted chain line may be connected to the video recording device as a separate unit. It may also be used by connecting it.

The input terminal 10 is an input terminal for a video signal to be recorded,
It is assumed that a composite color signal (hereinafter simply referred to as a composite signal) is input. Further, it is assumed that a video signal obtained by superimposing q-18- of the teletext signal is received by a receiving unit (not shown) and is applied to the input terminal 10. The composite signal is separated into a luminance signal (hereinafter referred to as Y signal) and a color signal (hereinafter referred to as C signal) in a Y/C separation circuit 14, and the Y signal is sent to a frequency modulator (hereinafter referred to as F and M modulation signal) via an adder 20. 22,
On the other hand, the C signal is directly applied to the frequency conversion circuit 26 and also to the burst gate circuit 18. The Y signal frequency-modulated by the FM modulator 22 is mixed with the C signal frequency-converted to a low frequency by the frequency converter 26 in the mixer 28, and is applied to the magnetic head 32 via the amplifier 30.
It is recorded on a recording medium such as a magnetic tape (not shown).

The composite signal is given to the horizontal synchronization separation circuit 12,
Here, the horizontal synchronizing signal is separated and applied to the pulse generating circuit 16 and switch 24. The pulse generation circuit 16 generates a pulse signal that is at H level during the color burst signal period in response to the horizontal synchronization signal, and provides the pulse signal to the burst gate circuit 18 as a gate signal, and also to the first PLL circuit 3.
The signal is also given to the hold circuit 40 in 4 as a control signal. The first PLL circuit 34 is a phase comparator 3 that responds to the color burst signal applied from the burst gate circuit 18.
6. It has an LPF 38 that applies the output of the phase comparator 36 to the hold circuit 40, and a VCO (voltage controlled oscillator) 42 whose oscillation frequency changes in response to the output of the hold circuit 40, and the output of the VCO 42 is connected to the phase comparator. 36 and to the second PLL circuit 46 via a 115 frequency divider 44.

Second (7) PLL circuit 46c Phase comparator 48, L P
It consists of a loop of an F50° VCO 52 and a 1/4 frequency divider 54, and the output of the VCO 52 is applied to the adder 20 via the switch 24. In addition, the above VC
A vXO (variable crystal oscillator) can be used as O42,52.

The recording system of FIG. 1 operates as follows. The burst signal extracted by the burst gate circuit 18 is given to the first PLL circuit 34, and the hold circuit 40 holds the signal from the LPF 38 at the period of the horizontal synchronization signal and outputs the signal from the VCO.
42, so as a result of the phase lock operation, the VCO
42 is the color subcarrier frequency f 3,579545M
Continuous oscillation at H2. This C f is frequency-divided by 115 by a 115 frequency divider 44 and given to the PLL circuit 46 in the second section. In the second PLL circuit 46, the output of the VCO 52 is given to the phase comparator 48 via the 1/4 frequency divider, so fX115 is multiplied by 4 (fx415), and the signal of approximately SCSC 2.88MHz is converted to VX Made by O52. This signal of approximately 2.88 MHz, that is, fX415, is applied to the adder 20 via the switch 24, which is closed only while the horizontal synchronizing signal e is present, so that it is superimposed on the horizontal synchronizing signal of the Y signal. Therefore, the fX415 signal as a pilot signal is superimposed on the horizontal synchronization signal of the Y signal, and a video signal is recorded on the recording medium.

FIG. 2 is a block diagram showing a reproduction system of an apparatus for realizing the recording and reproduction method of a video signal including a teletext signal according to the present invention.

The entire recording system shown in FIG. 1 may be incorporated into a video recording device such as a VTR, or only the portion shown by the dashed dotted line may be connected to the video recording device as a separate unit. It may also be used by connecting it.

The magnetic head 32 may be the same as the magnetic head 32 of the recording system shown in FIG. 1, or may be a magnetic head of a read-only machine without a recording system. The video signal picked up by the magnetic head 32 is sent to an amplifier 60, an FM demodulator 62, and a frequency conversion circuit 6.
4. A composite signal is generated through a well-known reproducing circuit consisting of a mixer 66. This composite signal is sent to the subtracter 70
, horizontal synchronization separation circuit 68, and one terminal of switch 74. The horizontal synchronization separation circuit 68 separates the horizontal synchronization signal from the composite signal and supplies it to the switches 74 and 72 as respective control signals, and also to the hold circuit 82 of the PLL circuit 76 as a control signal. The other terminal of the switch 34 is connected to the phase comparator 78 of the PLL circuit 76.
The phase comparator 78 forms a loop with the LPF 80, the hold circuit 82, the VCO 84, and the 1/2 frequency divider 86. The output of the 1/2 frequency divider is given to the subtracter 70 via a level/phase adjuster 88 and a switch 72.
The output of the subtracter 70 is applied to an output terminal 90 for a reproduced video signal. On the other hand, the output of the VCO 84 of the PLL 7B is given to the clock output terminal 92.

The reproduction system shown in FIG. 2 operates as follows. The horizontal synchronization separation circuit 6 uses the reproduced composite signal obtained from the mixer 6B.
The horizontal synchronization signal is separated at 8, which causes switch 7
4 is controlled and turned ON only during the period of the horizontal synchronization signal, so the pilot signal superimposed on the horizontal synchronization signal is extracted. This pilot signal is f
It is the C frequency of X415, is doubled by the PLL circuit 76, is made into a continuous signal, and is outputted from the clock output terminal 92 as a clock signal. fsc is 3.57954
At 5MHz, this clock signal is approximately 5.73MHz
It becomes z. This clock signal is divided into approximately 2 by 1/2 frequency divider 86.
．． 8 [iMHz signal, and is adjusted by the level/phase adjustment circuit 88 so that its level and phase match the level and phase of the pilot signal in the composite signal given to the adder 70, and horizontal synchronization is performed. It is applied to subtractor 70 only during the period of the signal.

Therefore, the pilot signal component superimposed on the horizontal synchronizing signal during recording is removed from the composite signal.

The clock signal obtained at the clock output terminal 92 in FIG. 2 is applied to the clock input terminal 94 in the character signal data extracting section of the teletext signal decoder shown in FIG. Compared to the conventional data extraction section shown in FIG. 4, the configuration in Figure 3 is simplified in that it does not require a circuit configuration to extract the color burst signal from the reproduced signal and generate a clock signal. . Other circuit configurations such as error correction are similar to those shown in FIG. 1 and will not be described repeatedly.

[Effects of the Invention] As is clear from the detailed explanation above, in the present invention, the clock signal used in the text signal data extracting section in the teletext signal decoder is used to record the video signal on which the teletext signal is superimposed. At the time of playback, this pilot signal is recorded as a pilot signal, and when it is played back, this pilot signal is separated to create a lock signal if necessary, so the relationship between the phase of character data and the phase of the clock signal remains constant even when affected by jitter. So, it no longer changes every field like before. Therefore, the framing code of each data packet can be accurately recognized, and there is no malfunction in which a teletext signal is mistakenly determined to be absent when it is present. Furthermore, since the character signal data itself is accurately decoded, once recorded by a video tape recorder, the teletext signal data can be reproduced satisfactorily without being erroneously decoded.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a recording system of an apparatus for realizing the method for recording and reproducing video signals including teletext signals according to the present invention;
FIG. 2 is a block diagram showing the reproduction system of the same device, and FIG. 3 is a block diagram of a character signal data extraction section in a decoder for teletext signals that uses the clock signal obtained by the reproduction system of FIG. 2. FIG. 4 is a block diagram of a character signal data extraction section in a conventional decoder. 12, 68...Horizontal synchronization separation circuit 14...Y/C separation circuit 16...Pulse generation circuit = 15-18...Burst game) 20...Adder 2
2...FM modulator 24, 72.74...Switch 28, 64...Frequency conversion circuit 28, [i6...Mixer 30. [fO
...Amplifier 32...Magnetic head 34, 46.76...PLL circuit 44.54.88
...Frequency divider 3B, 48.78-...Phase comparator 3
8.50.80-L P F2O, 82...Hold circuit 42.52.84...VCO62...FM
Demodulator 88...Level/phase adjustment circuit Inventor - Toyoide I Applicant Victor Japan Co., Ltd.

Claims (7)

[Claims] (1) When recording a signal in which a teletext signal is superimposed on a vertical retrace period of a video signal using a video signal recording device, a color burst signal of the video signal is used to create a pilot signal of a predetermined frequency; After the pilot signal is superimposed on the horizontal synchronizing signal section of the luminance signal separated from the video signal, the luminance signal is mixed with the color signal separated from the video signal and recorded, and at the time of reproduction, a video signal reproducing device A method of extracting the pilot signal from the horizontal synchronization signal in the reproduced video signal, creating a clock signal of a predetermined frequency based on the pilot signal, and extracting the teletext signal from the reproduced video signal based on the clock signal. A method for recording and reproducing video signals including teletext signals. (2) Claim 1, characterized in that the frequency of the pilot signal is 4/5 times the color subcarrier frequency.
A method for recording and reproducing a video signal including a teletext signal as described in 2. (3) means for separating a luminance signal and a color signal from an input video signal to be provided to a video recording device; means for separating a horizontal synchronization signal from the input video signal; and extracting a color burst signal in response to the color signal. means for generating a pilot signal of a predetermined frequency using the color burst signal; and means for superimposing the pilot signal on the luminance signal in response to the horizontal synchronization signal. (4) a first PLL circuit in which the means for generating the pilot signal is responsive to the color burst signal;
4. The apparatus according to claim 3, further comprising: a circuit for dividing the output signal of the PLL circuit; and a second PLL circuit responsive to the output signal of the frequency dividing circuit. (5) means for separating a horizontal synchronization signal from a video signal reproduced from a video reproduction device; and a clock of a predetermined frequency using a signal superimposed on a horizontal synchronization section of the video signal in response to the horizontal synchronization signal. and means for producing a signal. (6) The device according to claim 5, wherein the means for generating the clock signal is a PLL circuit. (7) means for generating a signal having a predetermined phase and frequency relationship with respect to the clock signal; means for intermittently transmitting this signal in response to the horizontal synchronization signal; Claim 5, characterized in that it has a means for subtracting a signal transmitted intermittently.
Apparatus described in section.