JPH0345086A - Video signal processing circuit - Google Patents

Abstract

PURPOSE:To ensure stable ghost cancelling by providing a discrimination circuit selecting directly an input video signal for a period when an OR between output detection signals of a synchronizing generating circuit and a specific line detection circuit is obtained and selecting a luminance signal for other period. CONSTITUTION:A specific line detection circuit 34 detects, e.g. the 18th horizontal line and the 281st horizontal line and supplies a detection signal (high level) to a discrimination circuit, that is, to an AND circuit 36. A synchronization generating circuit 35 based on the synchronizing signal generates a detection signal representing a period (pattern period) except the horizontal blanking period and gives it to the AND circuit 30. A high level signal is obtained from the AND circuit 36 only when a detection signal from each circuit is simultaneously inputted. The control signal controls a switch 32 to allow the switch 32 to select an input section 31 for only a period of the specific line and select other input section for other period thereby selecting a luminance signal output of a Y/C separator circuit 33. Thus, stable ghost cancelling is ensured.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention relates to a video signal processing circuit such as a video tape recorder, and in particular, the present invention relates to a video signal processing circuit such as a video tape recorder. This circuit is effective when processing a video signal into which a training signal of the following type is inserted.

(Prior Art) In the high-definition television broadcast system, a method has been considered in which a training signal (hereinafter referred to as an OCR signal) is inserted in advance on the transmitting side as a reference signal for a ghost cancellation circuit and then transmitted.

The OCR signal (Figure 6) is set to the 18th horizontal line and the 281st horizontal line, which have a corresponding relationship between fields of the video signal, as shown in Figure 7, and an eO82 type window is added to the slnx signal. A horizontal synchronizing signal and a color burst signal are added to the step signal which is multiplied and integrated. This signal is then combined with the pedestal signal level in an 8-field sequence and arranged as shown in FIG.

By the way, when the above video signal is supplied to a luminance/color signal (hereinafter referred to as Y/C) separation circuit as shown in Fig. 8, as shown in Fig. 9, the OCR signal and pedestal signal are As a result, the high frequency components of the previous line signal are superimposed. This is because the Y/C separation circuit separates a luminance signal using a 1-line delay circuit 11, a bandpass filter 12, and an adder 13, and a subtractor 14 that performs subtraction processing between the output of the bandpass filter 12 and the input video signal. This is because the color signals are separated using the chrominance signal, and the separation is performed using the correlation between the previous line and the current line. For this reason, when there is no correlation with the preceding and succeeding lines, as in the case of a GCR signal or a pedestal signal, there is a problem in that the high-frequency components of the preceding line are mixed in, as shown in FIG.

If such high-frequency components are mixed in, this will interfere with the ghost cancellation circuit, causing malfunction, and in the worst case scenario, the loop made up of the transversal filter of the ghost cancellation circuit may oscillate.

In addition, as a circuit that performs signal processing using the correlation between the front and rear horizontal lines, as a measure to improve the S/N of the color signal in a VTR, a color comb filter that removes adjacent crosstalk or a circuit that improves the S/N is used. A type comb filter is used.

FIG. 10(A) shows the configuration of a color comb filter,
The carrier color signal is supplied to a one-line delay circuit 21 and a subtracter 22. The subtracter 22 subtracts the output of the one-line delay circuit 21 from the input carrier color signal to derive a carrier color signal from which crosstalk components have been removed. However, as can be seen from a comparison between the input carrier color signal in FIG. 5B and the output carrier color signal in FIG.

FIG. 11(A) shows a recursive comb filter, which is composed of a subtracter 25 and a one-line delay circuit 26.

In this case, the input carrier fading signal in the same figure (B) and the same figure (C)
As can be seen by comparing the output carrier color signals of , the color signal of the previous line is mixed into the horizontal period of the GCR signal or pebbletal signal, and this mixed signal further affects the next line.

(Problems to be Solved by the Invention) As mentioned above, in the conventional video signal processing circuit,
When a video signal including a CGR signal or a pedestal signal is processed using correlation between fields, there is a problem in that unnecessary mixed signals are generated, which adversely affects the ghost cancellation circuit.

SUMMARY OF THE INVENTION An object of the present invention is therefore to provide a video signal processing circuit that prevents unnecessary mixed signals from being generated by OCR signals and pedestal signals by simple means and contributes to ensuring stable ghost canceling operation.

[Structure of the Invention] (Means for Solving the Problems) When there is a circuit that performs signal calculation using inter-field correlation, the present invention provides a horizontal line on which an OCR signal or a pedestal signal is superimposed on an input signal. It basically includes means for detecting a period and invalidating the above-mentioned calculation during this period.

The apparatus also includes means for inserting an alternative signal into the invalid period.

(Function) With the above means, it is no longer possible to obtain a calculation output using a GCR signal or a pedestal signal, and no unnecessary mixed signals are generated.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which an input video signal is supplied to an input section 31, and one input section of a switch 32, a Y/C separation circuit 33, and a specific line detection circuit 34 are connected to a synchronous It is supplied to a generator 35. Specific line detection circuit 3
4 detects, for example, the 18th horizontal line and the 281st horizontal line, and supplies the detection signal (high level) to a determination circuit, that is, an AND circuit 36. The synchronization generation circuit 35 is
Based on the synchronization signal, a detection signal indicating a section other than the horizontal retrace section (that is, a picture section) is generated and supplied to the AND circuit 36. The AND circuit 36 obtains a high-level output control signal only when detection signals from each circuit are input simultaneously. This control signal controls the switch 32 so that the switch 32 selects the input section 31 only in a specific line section, and selects the other input section during other periods to control the Y/C.
The brightness signal output of the separation circuit 35 is controlled to be selected.

As a result, the luminance signal output section 37 outputs the luminance signal separated by the Y/C separation circuit 35 and the OCR of the specific line section.
The signal and the pedestal signal are derived, and the color signal output section 38
A separated carrier color signal is derived.

FIG. 2 shows another embodiment of the invention.

A video signal is introduced into an input 41 and connected to one input of a switch 42 and a low-pass filter 4 for removing the carrier color signal.
3, a specific line detection circuit 44, and a synchronization generator 45. The output of the low-pass filter 43 is supplied to the other input part of the switch 42, and the switch 42 selects one of them according to the control signal and introduces the output to the Y/C separation circuit 46.

The specific line detection circuit 44 detects, for example, the 17th horizontal line,
The first horizontal line, the 280th horizontal line, and the 282nd horizontal line are detected, and detection signals are output from these line sections and supplied to the AND circuit 47. The synchronous generator 45 is
A detection signal indicating a section other than the horizontal retrace section is generated based on the synchronization signal and is supplied to the AND circuit 47. The AND circuit 47 obtains a high-level output control signal only when detection signals from each circuit are input simultaneously.

The switch 42 is switched to select the output of the low-pass filter 43 when the control signal from the AND circuit 47 is at a high level.

As a result, the signal input to the Y/C separation circuit 46 is
In the R signal and pedestal signal portions, a line (section of a specific line) where correlation is established between fields becomes a signal with high frequency components removed.

Therefore, unnecessary high frequency components are not mixed into the OCR signal and the pedestal signal.

As mentioned above, in the case of a video signal that includes a GCR signal or a pedestal signal, processing that spans between fields or frames will generate unnecessary mixed signals, so the circuit according to the present invention is used. By passing it through, you can eliminate the problem.

FIG. 3 shows yet another embodiment of the invention.

This circuit constitutes a noise reducer. The reproduced luminance signal is transmitted via the input section 61 to a one-line delay circuit 62,
It is supplied to one terminal of an adder 63 and a switch 64. The output of the one-line delay circuit 62 is supplied to an adder 63, and the output of the adder 63 is supplied to the other terminal of the switch 64. The one-line delay circuit 62 and the adder 63 constitute a vertical filter and can reduce noise. Here, the switch 64 is the AND circuit 36 in the previous embodiment.
Or controlled by a control signal similar to the output of 56,
The specific line section is derived by directly selecting the luminance signal of the input section 61. This prevents unnecessary high-frequency components from being mixed into the flat signal on a specific line.

FIG. 4 shows an embodiment in which the present invention is applied to yet another noise reducer.

The reproduced luminance signal from the input section 71 is supplied to one input section of the switch 72 and the coefficient multiplier 73 . The output of the coefficient unit 73 is supplied to a subtracter 74. The output of this subtracter 74 is
It is supplied to the other input of switch 72 and to field or frame delay circuit 75. The output of this delay circuit 75 is passed through a coefficient unit 76 to a subtracter 74.
is supplied to Here, if the coefficient of the coefficient unit 73 is K, then
The coefficient of the coefficient unit 76 is (1-K). In this circuit as well, the switch 72 is the AND circuit 3 in the previous embodiment.
6 or 56, and the specific line section is derived by directly selecting the luminance signal from the input section 61. This prevents unnecessary high-frequency components from being mixed into the flat signal on a specific line.

FIG. 5 shows yet another embodiment of the invention.

This embodiment is provided in the path after the carrier color signal and luminance signal are separated. For example, the video signal recorded on magnetic tape in a VTR is a normal signal,
If the signal does not include an OCR signal, it is preferable to remove high-frequency components in the portion corresponding to the position of the GCR signal. The embodiment shown in FIG. 3 is a circuit that realizes the above function.

A luminance signal is supplied to the input section 52. The carrier color signal at input 51 is guided to one input of switch 53. A constant voltage V1 is supplied to the other input of the switch 53. On the other hand, the luminance signal from the input section 52 is supplied to a specific line detection circuit 54 and a synchronization generator 55.

The specific line detection circuit 54 detects, for example, the 18th horizontal line and the 281st horizontal line, and supplies the detection signals to the AND circuit 56. The synchronization generation circuit 55 generates a detection signal indicating a section other than the horizontal retrace section based on the synchronization signal, and supplies it to the AND circuit 56. The AND circuit 56 obtains a high-level output control signal only when detection signals from each circuit are input simultaneously. This control signal controls the switch 53, and the switch 53 is used only in a section of a specific line.
selects the constant voltage v1 side, and during other periods the input section 51 selects and outputs it as a carrier color signal output.

Further, this carrier color signal is added to the input luminance signal in an adder 57.

According to the above embodiment, the carrier color signal is at a constant DC level on a particular line. Therefore, since the video signal combined with the luminance signal has high frequency components removed at the position of the OCR signal, this video signal can be input to the ghost canceling circuit.

[Effect of the invention] As explained above, this invention can achieve OC by simple means.
It is possible to prevent unnecessary mixed signals from being generated by the R signal and the pedestal signal, and contribute to ensuring stable ghost canceling operation.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of this invention, and FIGS. 102 to 5 are circuit diagrams showing other embodiments of this invention, respectively.
FIG. 6 is a waveform diagram showing the reference signal used for ghost cancellation, FIG. 7 is a waveform diagram showing the insertion position of the reference signal with respect to the video signal, and FIG. 8 is a diagram showing the Y/C separation circuit.
FIG. 9 is an explanatory diagram showing problems when a video signal having a base ring signal is supplied to a conventional Y/C separation circuit;
11 and 11 are explanatory diagrams for explaining problems and the like when a video signal having a reference signal is input to a conventional comb filter. 32.42.64.72.53...Switch, 33.
46...Y/C separation circuit, 34.44.54...Specific line detection circuit, 35.45.55...Kaimei generator, 36,47.56...AND circuit.

Claims (3)

[Claims] (1) A switch to which an input video signal is supplied to one input; and a switch to which the input video signal is supplied, separates a luminance signal and a chrominance signal, and supplies the separated luminance signal to the other input of the switch. a luminance/chrominance signal separation circuit that detects a predetermined specific horizontal line that corresponds between fields of the input video signal and outputs a detection signal for that line section; a synchronization generation circuit to which a video signal is supplied, detects a period (picture part) other than the horizontal retrace period, and generates a detection signal for that period; and a logical sum of the output detection signals of the synchronization generation circuit and the specific line detection circuit. The apparatus further comprises a determination circuit that controls the switch to directly select the input video signal only during the period in which the input video signal is obtained, and selects the luminance signal from the luminance/chrominance signal separation circuit during other periods. video signal processing circuit. (2) a filter to which an input video signal is supplied and which removes components in the color signal band of the video signal; the input video signal is supplied to one input section, and the output of the filter is supplied to the other input section; a switch that supplies the selected output to a luminance/chrominance signal separation circuit; a specific line detection circuit that is supplied with the input video signal and detects horizontal lines before and after a predetermined specific horizontal line; and the input video signal. is supplied, a synchronization generation circuit detects a period other than the horizontal retrace period and generates a detection signal for that period, and only the period in which the logical sum of the output detection signals of the synchronization generation circuit and the specific line detection circuit is obtained. , a determination circuit that controls the switch to select the output connection of the filter and guides the input video signal to the luminance/chrominance signal separation circuit during other periods. circuit. (3) A switch in which a reproduced color signal in a video tape recorder is supplied to one input part, a predetermined DC voltage is supplied to the other input part, and leads a selected output to a luminance/color signal mixing circuit; a specific line detection circuit that is supplied with a reproduced luminance signal in a recorder, detects a predetermined specific horizontal line that has a corresponding relationship between fields, and outputs a detection signal for that line section; and the video tape. A synchronization generation circuit is supplied with the reproduced luminance signal in the recorder, detects a period other than the horizontal retrace period, and generates a detection signal for that period, and a logical sum of the output detection signals of the synchronization generation circuit and the specific line detection circuit is provided. A video signal processing circuit comprising: a determination circuit that controls the switch to select the other input section only during the obtained period, and selects the reproduced color signal during other periods.