JPS6017977Y2 - dropout compensator - Google Patents

Description

[Detailed description of the invention] The present invention relates to a dropout compensation device, which uses a charge transfer element as an analog memory to eliminate partial loss of information (dropout) in an input signal with an extremely simple circuit configuration. The purpose is to provide a device that can compensate.

Conventionally, in order to compensate for dropouts in video signals reproduced from, for example, magnetic recording and reproducing devices, I
Either by using an H delay line (H is a horizontal scanning period) or by A/D converting the reproduced video signal and using an 8-bit digital semiconductor memory element of 1H, which is supplied as an 8-bit parallel digital signal. , when a dropout occurs, it is replaced with the video signal from before IH.

However, the IH delay line described above is expensive, and conventional devices using the semiconductor memory element require an A/D converter at the input stage and a D/A converter at the output stage of the semiconductor memory element. The disadvantages are that it is expensive, the peripheral circuitry is extremely complex, and the overall size of the device is large.

The present invention eliminates the above-mentioned drawbacks, and an embodiment thereof will be described below with reference to the drawings.

FIG. 1 shows a block diagram of an embodiment of a dropout compensator according to the present invention.

In the figure, reference numeral 1 denotes an input terminal through which, for example, a reproduced video signal enters and is supplied to the video sensor 2 and analog gate 3, respectively.

The image sensor 2 is a charge coupled device (CCD) which will be described later in synchronization with the clock pulse from the input terminal 6.
The output video signal from the input terminal 5 is compared with the reproduced video signal from the input terminal 1, and it is determined that dropout has occurred only during the period when there is a large level difference between the two, and the analog gate 3 is closed. open.

During the period where there is almost no level difference between the two human power signals of the video sensor 2, the output of the video sensor 2 causes the analog gate 3 to
is opened and analog gate 4 is closed.

Therefore, during a period when dropout does not occur, the reproduced video signal from the input terminal 1 passes through the analog gate 3 and is supplied to the CCD 5 as an analog memory, where it is synchronized with the clock pulse from the input terminal 6 to the IH. will be delayed.

The clock pulse from the input terminal 6 has an input signal of N
In the case of a TSC color video signal, the frequency is usually selected to be three or four times the color subcarrier frequency of 3.58 MH2.

The video signal taken out from the CCD 5 is output to the output terminal 7.
On the other hand, it is supplied to the video sensor 2 and the analog gate 4.

On the other hand, if a dropout occurs in the input playback video signal, for example, the 2H of the input playback video signal as shown in FIG.
If the second period is missing, the video sensor 2 detects Kawaguchi's dropout, and the detection output opens the analog gate 4 and closes the analog gate 3, so the IH-th video signal from the CCD 5 becomes analog. It is fed back to the input of the CCD 5 via the gate 4, and thereby the output of the video signal output from the output terminal 7 is replaced with the <IH-th video signal as shown by a in FIG. 2B.

Note that in FIGS. 2A and 2B, the video signal and color burst signal during the video period are omitted, and for convenience of explanation, only the horizontal synchronization signal is shown.

In general, it is unlikely that a video signal will be missing consecutively over IH, and taking into account the so-called line correlation, in which the video signals of the Japanese and American standards are extremely similar in information in periods adjacent to IH, the output terminal 7, a dropout-compensated video signal of good quality is taken out.

In this example, CCD 5 is used as the analog memory, so there is no need to use an A/D converter or D/A converter compared to conventional ones, and since CCD is suitable for integrated circuits, it is extremely small. , a lightweight device can be constructed.

Note that although a CCD was used as the analog memory in the above embodiment, other charge transfer devices such as a packet brigade device BBD may also be used.

As mentioned above, the dropout compensation device according to the present invention is
a first gate that passes or blocks an input signal such as a video signal having similar information content for each predetermined period; and a charge transfer element that delays the input signal that has passed through the first gate for the predetermined period and outputs the delayed signal. a second gate that allows the output signal of the charge transfer element to pass through and returns it to the input side of the charge transfer element or blocks it; and a second gate that controls the output signal of the charge transfer element and the input signal, respectively. When the level difference between the two signals is smaller than a certain value, the first gate is opened and the second gate is closed. When the level difference between the two signals is larger than the certain value, the above gate is opened. Since the sensor controls the first and second gates to close the first gate and open the second gate, when a dropout occurs in the input signal, the input signal from the predetermined period of time Since the charge transfer element can be replaced with a signal, dropout can be compensated for, and the charge transfer element described above is suitable for integrated circuits, and the repeating circuit is extremely simple, so the entire device can be extremely miniaturized.
It also has the advantage of being relatively inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a block system diagram showing an embodiment of the device of the present invention;
2A and 2B are signal waveform diagrams for explaining the operation of FIG. 1, respectively. 1... Playback video signal input terminal, 2...
Video sensor, 5... Charge coupled device (CCD), 6... Clock pulse input terminal, 7... Playback video signal output terminal.

Claims (1)

[Scope of utility model registration request] a first gate that passes or blocks an input signal such as a video signal having similar information content before and after a predetermined period; and a first gate that delays the input signal that has passed through the first gate for the predetermined period. a second gate that passes the output signal of the charge transfer element and returns it to the input side of the charge transfer element or blocks it; The levels of the input signals are compared with each other, and when the level difference between both signals is smaller than a certain value, the first gate is opened and the second gate is closed, so that the level difference between both signals is the same as above. The sensor controls the first and second gates so as to close the first gate and open the second gate when the charge transfer element is larger than the charge transfer element. A dropout compensator configured to obtain.