JPS61147684A - Address code reproducing device - Google Patents

Abstract

PURPOSE:To decrease an error rate by mounting a controlling circuit which is outputting the first code signal proceeding by one horizontal period in a drop-out compensating circuit when the following second code signal is judged an error code and reproducing an address signal through the first code signal. CONSTITUTION:When any drop-out is found in a picture number code PN2 inserted in 18th horizontal period, it is complemented in a compensating circuit 2 by a picture number code PN1 in proceeding 17 horizontal period. Even when the picture number code PN2 inserted in the 18th horizontal period is not complemented by means of micro drop-out, etc. and outputted as fault data, or disk on which faulty PN2 is recorded in manufacturing process of disks is reproduced, it is possible to control the reproduction of an accurate address code and decrease the error rate by outputting the picture number code PN1 inserted in the 17th horizontal period.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a circuit for forming an address code for controlling a playback device from a disc on which information and various control signals related to the information are recorded. involved,
In particular, the present invention relates to an address code reproducing device suitable for detecting address codes on video discs.

[Conventional technology]

2. Description of the Related Art Optical reproducing devices have been put into practical use that track spiral or concentric tracks on which information is recorded using a laser beam and read out high-density recorded information from the reflected light.

In such a playback device, when the recorded information is composed of video signals, the rotation speed is controlled so that one image signal is obtained with one revolution of the disc.
(Constant Angular V alo
-city) system and CLV (Consta city) system that controls the rotation speed so that the reproduction line speed is constant.
ntLinear Velocity) method has been developed, but in either method, various control signals are inserted into the vertical blanking period of the video signal, and various controls of the playback device are performed by reading these control signals. It is being said.

As a control signal, the innermost track (900
) rack) is inserted into the lead-in cord (88F
FFF), lead-out code (80EEEE) inserted in the outermost track (600 tracks), picture number code (frame number code), picture stop code, and chapter number added to each frame along with the video signal. There are codes etc.

In particular, according to the Philips standard, the majority of these control signals are located within the vertical blanking period.
It is inserted in the 7th horizontal period and the 18th horizontal period,
Among them, a code signal indicating a frame number can be said to be an important code in forming an address signal when searching a predetermined screen from a programmed image.

FIG. 3 shows a part of the video waveform indicating the position of the frame number (hereinafter referred to as picture number), and shows the 17th horizontal period following the vertical synchronization signal VD.
In the 18th horizontal period (hereinafter simply referred to as 17H and 18H), picture number codes PNI and PN2 made of the same code corresponding to the frame are inserted.

Figure 4 shows the bit structure of the picture number.
H is a horizontal synchronization signal, C is a burst signal.

B O+ Bl + B2 +・・・・・・・・・B2
3 indicates a pie face digital code consisting of 24 bits.

The picture number is a 4-bit code signal F.

X l + X 2 + X 3 + X 4 + X
It is recommended to record as a 6-digit numerical value consisting of 5, and frame numbers 1 to 99999 are sequentially assigned to x and -x5.

FIG. 5 is a block diagram showing an outline of a conventional playback device that reads out picture numbers inserted in the 17H and 18H periods, in which 1 shows a photoelectric element 1a that converts reflected light from the disc into an electric signal, and a played back video signal. 2 is an IH pickup device equipped with a preamplifier 1b etc. that amplifies the
A dropout compensation circuit includes a delay circuit 2a, FM demodulation circuits 2b and 2c, a dropout detection circuit 2d, and a switch circuit 2e whose inversion is controlled by a signal that detects dropout; 3 is a synchronization signal separation circuit; 4 is 1
A gate signal generation circuit 5 generates a gate signal for extracting the 8H period signal, 5 is a gate circuit, and 6 decodes the code signal inserted in the 18H period extracted by the gate circuit 5 to form an address code. It is a digital signal processing circuit.

Since the conventional address code reproducing device for searching image frames has the above-described configuration, the reproduced RF signal S output from the pickup device 1 is first processed by the well-known IH delay circuit 2a. Dropouts are removed by a dropout compensation circuit 2 including the following.

That is, when a dropout of the disc is detected by the dropout detection circuit 2d, the switch circuit 2e is switched to complement the pre-IH signal for the dropout and output it.

The video signal from which the dropout has been removed is supplied to a video signal processing circuit (not shown), while the gate signal (wind pulse) corresponding to the 18H period is converted into a gate signal based on the synchronization signal extracted by the synchronization signal separation circuit 3. Since the signal is input to the gate circuit 5 which is supplied from the generation circuit 4, the gate circuit 5 outputs a signal for the 18H period, that is,
Picture number code PN2 is extracted and supplied to digital signal processing circuit 6.

Therefore, at least when a track of a video portion is being reproduced, an address signal corresponding to a picture number is detected by the digital signal processing circuit 6 for each frame.

Then, the playback device is controlled based on the detected address signal to search for a specific screen or to play back a still image on a specific screen.

In the case of the conventional example described above, the vertical blanking period is 17
Since the picture numbers inserted in the H and 18H periods are formed by the same code, the second code signal inserted in the 18H period is, for example, picture number code PN2, and dropout occurs at this point. However, since the first code signal inserted in the 17H period, that is, the picture number code PNI, is supplemented, the probability that an erroneous address signal will be generated due to dropout is reduced.

[Problem that the invention seeks to solve]

However, even if a picture number is extracted and an address signal is generated using this method, the error rate is only about 10-5 at most, and some mass-produced discs are difficult to search for a predetermined frame. There are some discs that cannot be used to form still images, and the manufacturing yield of discs cannot be said to be low.

One of the reasons for this is that there are problems with various processes in the disc manufacturing technology. For example, it is possible that dropouts occur simultaneously during the 17H and 18H periods. The control signal being used may not be corrected correctly.

An error in the code of the control signal inserted during the 18H period during the mastering process also causes an increase in the error rate.

The present invention has been made to solve these problems, and in particular to provide an address code reproducing device that further improves the error rate of picture number codes that form address signals during still image reproduction. .

[Means for solving problems]

The address code reproducing device of the present invention normally reproduces an address signal from a subsequent second code signal in the same picture number that is consecutively inserted into two predetermined horizontal periods of a vertical blanking period. However, when an error is detected in the second code signal when the playback device is in the still picture mode, the dropout compensation circuit outputs the preceding first code signal, Control is performed to reproduce an address signal from this first code signal.

[Effect]

In the normal playback state, the address signal is formed by the subsequent second code signal inserted in two horizontal periods, but when it is determined that this second code signal is erroneous, the preceding Since the code signal of 1 is input to the digital signal processing circuit to form an address code, an address signal with an even lower error rate than the conventional address code reproduction method can be obtained.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the address code reproducing device of the present invention, and 2A is an external terminal E from which a pre-IH signal can be forcibly extracted from the outside for the dropout compensation circuit 2. , and an OR gate 0 are provided. 3 and 4 indicate a synchronizing signal separation circuit and a gate signal generation circuit for generating a gate signal for extracting the signal of the 18H period, and the gate signal is supplied to the gate circuit 5. 7 is a shift register into which the signal output from the gate circuit 5 is read, 8 is a clock signal generation circuit, 9 is an incorrect code detection circuit that detects errors in the picture number code, and 10 is set by the incorrect code detection circuit 9. , is a flip-flop that is reset by NS when the disc playback device is not in the steal mode. Note that 6 is a digital signal processing circuit that forms an address signal from the picture number code.

The erroneous code detection circuit 11 uses the above-described bit configurations F, XI, X2, . Xa, Xa.

x5 is being monitored and the first 4 bits are 1111 (F)
or XI, X2. in the second to sixth digits. X
When the values of a, Xa, and X5 are not numbers from 0 to 9, that is, A, B, C, D, and E are used in hexadecimal.
, F, the data may be determined to be erroneous data.

Since the address code reproducing apparatus of the present invention has the above-described configuration, the picture pick-up code PN2, which is normally inserted in the 18H period as in the conventional address code reproducing apparatus, as shown in FIG. is output from the dropout compensation circuit 2A, extracted by the gate signal WP in the gate circuit 5, stored in the shift register 7, read out at a predetermined speed, and input to the digital signal processing circuit 6 to obtain the address. A signal is formed. When there is a dropout in the picture number code PN2 inserted in this 18H period, the preceding one in the dropout compensation circuit 2
It is complemented by the picture number code PN in the 7H period.

However, when the disc playback device enters the still picture playback mode, the reset of the flip-flop 10 is released, so in this state, the picture number code PN2 of the 18H period is output from the shift register 7.
When the error code detection circuit 11 detects that there is an error in the code, the output E[ causes the flip-flop 1
o is in the set state, and an "H" level signal is input to the controller A. Then, due to the gate signal WP output from the gate signal generation circuit 4, a signal that is at the H" level only for the 18H period is output to the drop-out compensation circuit 2.
The switch circuit 2e is forcibly inverted via the OR gate 0 of A. Therefore, the IH-delayed 17H period signal, that is, the preceding picture number code PN+
passes through the gate circuit 5 during the 18H period, is read into the register 7, and is further input to the digital signal processing circuit 6.

Therefore, when the picture number code PN2 inserted during the 18H period is not supplemented by micro dropout etc. and is output as incorrect data, or when a disc with an incorrect picture number code PN2 recorded during the disc manufacturing process is 17 even when playing
Picture number code PNI inserted in H period
[Effects of the Invention] As explained above, the address code reproducing device of the present invention is inserted into a predetermined position of a vertical blanking period for two consecutive horizontal periods. Among the picture number codes, when it is determined that there is an error in the subsequent second code signal that is normally output, the preceding first code signal before IH is output from the dropout compensation circuit. With this configuration, even when the second code signal is not corrected to the correct code signal or is incorrect, especially when playing still images, the address can be corrected by the preceding first code signal. It has the advantage of being able to regenerate signals and lower error rates than conventional address code reproducing devices.

Furthermore, since the error rate is reduced, the production yield of disks is improved.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an address code reproducing device showing an embodiment of the present invention, Fig. 2 is an explanatory diagram of the operation of detecting a picture number in Fig. 1, and Fig. 3 shows the insertion position of the picture number code. Video signal waveform diagram, 4th
The figure is a waveform diagram showing the bit configuration of the control signal.
The figure is a block diagram for conventional picture number detection. In the figure, 2A is a dropout compensation circuit, 3 is a synchronization signal separation circuit, 5 is a gate circuit, 6 is a digital signal processing circuit,
9 indicates an erroneous code detection circuit.

Claims (1)

[Claims] When there is a dropout in the playback signal of the disc, the dropout compensation circuit is configured to output the signal of one horizontal period before, and the dropout compensation circuit is configured to output the signal of one horizontal period before the two consecutive horizontal blanking signals at a predetermined position within the vertical blanking period. In a playback device that detects a second code signal following a picture number consisting of the same code inserted in a period and outputs an address code, it is determined that the subsequent second code signal is error data. 1. An address code reproducing device comprising: a control circuit for outputting a first code signal that precedes the dropout compensation circuit by one horizontal period when the dropout compensation circuit occurs.