JPS6346930Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a random access circuit that does not malfunction.

Optical video discs record frame numbers on recording tracks, and the video disc player that plays them is equipped with a random access mechanism to search for a designated position. This random access mechanism identifies the motor access range and the mirror access range by comparing the playback frame number played by the pick-up with the specified frame number, and in the motor access range, plays information toward the center of the mirror access range. The pickup is forcibly transferred without any movement, and in the mirror access range, depending on the distance to the specified position, the playback speed is gradually reduced to 10x playback, 5x playback, normal playback, and still image playback at the specified position. However, this random access mechanism detects a match between the playback frame number and the specified frame number and ends the access operation, so if the playback of the frame number that matches the specified frame number is not detected due to adhesion of dust, etc. is accessed repeatedly and becomes inaccessible.

Therefore, the present invention has developed a new and effective header that detects frames that precede the originally designated frame and enables access to the originally designated frame by retroactively changing the designated frame number every time an access error occurs. This paper aims to propose an access circuit.

The present invention will be described below with reference to illustrative embodiments. In this embodiment, a designated frame number is set and stored in a frame number setting circuit 1, a frame number to be played back is latched in a frame number latch circuit 2, and a comparison circuit 3 compares both frame numbers to determine this value. The comparison output is input to four detection circuits. First, as a result of the comparison, if the playback position precedes the mirror access range, the forward access detection circuit 4 is activated, and if the playback position is within the mirror access range, the mirror access range detection circuit 5 is activated. Furthermore, if the playback position matches the specified frame number, the coincidence detection circuit 6 is activated, and if the playback position is beyond the mirror access range, the reverse direction access detection circuit 7 is activated. When the forward direction access circuit 4 or the reverse direction access circuit 7 is activated, the polarity detection output and speed control output are input to the motor drive circuit 8, and the pickup is moved to the mirror access range by the pickup moving motor (not shown) without reproducing information. It is moved toward the center of the screen. When the mirror access circuit 5 is activated, the pick-up latches the frame number and selects 10 times according to the interval to the specified position.
An interlaced pulse is input to the mirror drive circuit 9 so as to perform double speed playback → five times speed playback → normal playback. Furthermore, if the coincidence detection circuit 6 is activated, the access end detection circuit 10 is activated so that reproduction of the specified position can be continued.
An interlaced pulse for still reproduction is input to the mirror drive circuit 9. The feature of this embodiment is that if the frame number matching the specified frame number cannot be reproduced due to an obstacle such as dust or scratches, re-access is repeated using the preceding frame number as a clue. . That is, the first flip-flop 11, third flip-flop 13, and up-down counter 14 are reset in advance by a reset pulse inputted at the start of access, and when the pick-up once reproduces the mirror access range, the mirror access range detection is performed. The output of the circuit 5 puts the first flip-flop 11 in the set state, while the second flip-flop 12 goes in the reset state, and when the pick-up goes out of the motor access range without reproducing the designated frame number, the backward access detection circuit The second flip-flop 12 is set to the set state by the output of 7, and the content of the frame number setting circuit 1 is decreased by 1 via an AND circuit, while the content of the up-down counter 14 is set to "1".
It is configured to count up and re-access the frame preceding the designated frame number by one frame. This access is repeated many times until the frame number of the frame number setting circuit 1 and the reproduction frame number match, and each time there is an access error, the contents of the frame number setting circuit 1 are counted down and the contents of the up-down counter 14 are counted down. The search position is changed by counting up. Therefore, when the coincidence detection circuit 6 is activated by the second and subsequent accesses, the third flip-flop 13 is set, and the latch pulse generated at the frame period via the AND gate in the subsequent stage is applied to the up-down counter 14. is counted down, and upon detecting that the contents of the up-down counter 14 have become "0", the access completion detection circuit 10 continues to apply skip pulses for still reproduction to the mirror drive circuit 11, and the access end detection circuit 10 continues to apply skip pulses for still reproduction to the mirror drive circuit 11. Perform still playback.

Therefore, according to the present invention, since the search position is traced back every time there is an access error and the access is repeated, even if the specified frame number cannot be reproduced, access is possible, which is very effective.

[Brief explanation of drawings]

The figure shows a circuit block diagram according to an embodiment of the present invention. Explanation of main figure numbers: 1... Frame number setting circuit, 2... Frame number latch circuit, 13... Up-down counter, 10... Access end detection circuit.

Claims (1)

[Scope of utility model registration request] The setting output of the frame number setting circuit that sets and stores the designated frame number is compared with the latch output of the latch circuit that latches the playback frame number, and the pickup is forcibly transferred to the mirror access range preceding the designated frame, and the mirror access range is In the random access mechanism for accessing a specified frame by controlling skipping of the tracking mirror of the pickup to be reproduced, the frame number setting circuit counts down the specified frame number each time the specified frame is out of the mirror access range after accessing the mirror; , an up-down counter that counts up every time it goes out of the mirror access range after mirror access, and counts down at the frame period after the set output and latch output match, and the up-down counter that returns to the initial state after the set output and latch output match. A random access circuit is provided with an access end detection circuit that detects the current state and generates a jump pulse for still playback.