JPS641868B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recorded information reproducing apparatus, and more particularly to a recorded information reproducing apparatus including an address signal for information retrieval.

In addition to video and audio information, a recording medium such as a video disk includes an address signal to facilitate retrieval of this information.

On the other hand, since the dropout phenomenon in the reproduced signal is unavoidable, a dropout compensation device is often added to compensate for the reproduced signal.
In the case where such a dropout compensation function is provided, if a dropout occurs in the period corresponding to the address signal in the reproduced signal, dropout compensation will naturally be performed and the signal will be replaced with the previous signal, for example, 1H (one line) during that time. As a result, not only a normal signal is not derived as the address signal, but also a completely different compensation signal is derived, which is undesirable because it causes malfunctions in information retrieval and significantly reduces its reliability.

Therefore, it is an object of the present invention to provide a recorded information reproducing apparatus which stops the dropout compensation operation when a dropout occurs in an address signal section, thereby preventing the dropout from being replaced with an erroneous address signal, etc. It is an object.

Hereinafter, the present invention will be explained using the drawings.

The figure is a schematic block diagram showing an embodiment of the present invention, in which the reproduced RF signal including the address signal is transmitted to the demodulator 1.
After being demodulated by and amplified by an amplifier 2, the signal is applied to a switching circuit 3 for dropout compensation. The reproduced RF signal is input to the 1H delay circuit 4, delayed by 1H, demodulated by the demodulator 5, amplified by the amplifier 6, and input to the switching circuit 3. Further, a dropout detection circuit 7 is provided to detect a dropout in the reproduced RF signal, and the high level detection signal becomes one input of a two-input AND gate 8, and the output of this gate becomes a switching control signal for the switching circuit 3.

The output of the switching circuit 3 directly becomes a video signal output, and is also inputted to a sync separation circuit 12 and an address separation circuit 13 via an LPF 9, an amplifier 10, and a pedestal clamp circuit 11. An address section detection circuit 14 is provided which detects an address signal insertion section from the synchronization separation output of the synchronization separation circuit 12 and generates a low-level detection signal.The address separation circuit 13 outputs a clamp output during the existence period of this detection signal. address signals are gated and separately derived. Here, since the address signal is inserted within a certain period of the synchronization signal, for example, the vertical blanking period, the address period detection circuit 14 detects the initial timing of the vertical synchronization signal and then It is configured to generate a detection signal with a predetermined width after a period of delay, and use this as a gate pulse.

In the present invention, the address section detection signal is provided as the other input of the two-input AND gate.

In such a configuration, in a normal operating state without dropout phenomenon, the dropout detection signal is at a low level, and the address interval detection signal is at a high or low level, so the output of the AND gate 8 is at a low level. Therefore, if the switching circuit 3 is controlled to select the output of the amplifier 2 at this time, a regular video signal, synchronization signal, and address signal will be output.

Next, if a dropout occurs outside the address interval, the dropout detection signal transitions to a high level, and since the address interval detection signal remains at a high level, the output of the AND gate 8 becomes a high level, and switching is performed. The circuit 3 selects the output of the amplifier 6 and outputs a signal delayed by 1H to perform dropout compensation.

Furthermore, since the address interval detection signal transitions to a low level in the address interval, even if a dropout occurs in the address interval, the output of the AND gate 8 becomes a low level, and the switching circuit 3 selects the output of the amplifier 2, thereby causing a dropout. No compensatory action will be taken. Therefore, it is advantageous that erroneous address information or the like is not replaced in the address section.

By the way, if there is a dropout in the address area, part of the data will be destroyed.
In general, dropouts in video disc systems are short, so if compensation is made for this dropout, the signal will be replaced over an area longer than the destroyed portion. In this case, the address signal has no correlation with the data from 1H before, and the data destruction will further expand, exceeding the code error correction ability and increasing the probability that the data cannot be read.

In other words, since there is a line correlation for video signals, it is possible to compensate for dropouts by replacing the signal with a signal from 1H earlier, but in the case of address signals, data will be destroyed regardless of whether compensation is used or not. If dropout compensation is not performed, the degree of destruction will be much smaller, and the probability that it will be within the code error correction capability will be higher. Data destroyed by dropout can be compensated for by code error correction, so dropout compensation is not required in the address area. By prohibiting the operation, malfunctions can be prevented.

As described above, in the present invention, since a dropout in an address section is not replaced with a signal delayed by 1H, an erroneous address is not inserted, and erroneous retrieval does not occur.

It should be noted that the block diagram shown above merely shows an example, and it goes without saying that various modifications can be made.

[Brief explanation of drawings]

The figure is a block diagram showing an embodiment of the present invention. Explanation of symbols of main parts, 3...Signal switching circuit,
7... Dropout detection circuit, 8... AND gate, 14... Address section detection circuit.

Claims (1)

[Claims] 1. A recorded information reproducing apparatus having a dropout compensation circuit that detects a dropout in a reproduced signal of recorded information including an address signal for information retrieval and performs dropout compensation, wherein the address signal is inserted into the output signal of the dropout compensation circuit. A recorded information reproducing apparatus comprising: means for detecting a period and generating a detection signal during the period; and means for stopping the compensation operation of the dropout compensation circuit during the period during which the detection signal is generated.