Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
1998-12-04
2001-05-22
Huber, Paul W. (Department: 2651)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S033010, C369S124080
Reexamination Certificate
active
06236631
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus which reproduces signals from an optical disk such as a DVD-ROM, and in particular to an apparatus which detects a frame number in the reproduced signals.
2. Description of Prior Art
Recently, an optical disk has been developed to record and reproduce information optically with a laser light, and various formats are proposed to record information in an optical disk. Synchronizing signals are necessary in any format. When an optical disk is reproduced, the synchronizing signals are reproduced and counted, and a frame is decided according to the count value. That is, a frame is detected by counting the synchronizing signals. However, when a disk is rotated anomalously, the time length for a frame becomes longer or shorter. Then, synchronizing signals is counted erroneously, and it becomes uncertain which frame in a sector is reproduced. Thus, the reproduced signals are all erroneous.
Japanese Patent laid open Publication 8-289249/1996 describes an apparatus and a method for solving this problem. A recording medium or DVD-ROM has digital data in the DVD-ROM format wherein a sector consists of lines, each line consisting of frames of odd numbers and those of even numbers. A frame consists of synchronizing signals (of sync numbers) and data. In the DVD-ROM format, a synchronizing signal has one of predetermined patterns, and when a DVD-ROM is reproduced, a frame number is detected according to a combination of at least two, or preferably consecutive three or four synchronizing signals for the sake of stability of the frame number detection.
However, in the DVD-ROM format, because only a 13-bit pattern is varied in the synchronizing signals, a distance between two synchronizing signals becomes very short. If the bit length of the pattern of synchronizing signal is short, possibility of erroneous detection of frame numbers increases. On the other hand, if the bit length of the pattern in the synchronizing signal is increased, data efficiency becomes worse. If the number of synchronizing signals necessary for the determination of frame number is increased, the probability of erroneous detection is decreased. However, no errors cannot be allowed, and a ratio for the correct detection of frame number is liable to be decreased. Therefore, it is desirable to detect a frame number correctly in the data including synchronization patterns of short code distances between them.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an apparatus and a method for detecting a frame number in the signals consisting of synchronization pattern of short code distances between synchronization patterns, without erroneous detection of frame number.
An apparatus according to the invention detects frame number from input signals. The input signals consist of a plurality of sectors, a sector consisting of a plurality of frames, a frame including synchronizing signals and data, the synchronizing signals having a pattern used to identify a frame number in a sector, the pattern being defined to identify a frame number from a pattern of the synchronizing signals in a frame or from patterns of the synchronizing signals in consecutive frames. In the apparatus, a pattern of synchronizing signals is extracted for consecutive X frames from input signals where X is a natural number. Then, the extracted pattern of the extracted synchronizing signals is compared with a predetermined pattern to determine whether the extracted pattern agrees with the predetermined pattern by at least Y frames or not, wherein Y is a natural number smaller than the predetermined number of consecutive frames. Then, a frame number is determined based on an output signal of the comparison.
In an example, a block consists of Z frames of the extracted pattern of synchronizing signals (for example, Z=2). The extracted pattern of synchronizing signals is compared with a predetermined pattern to determine whether the extracted pattern agrees with the predetermined pattern by at least Y blocks or not, wherein and Y and Z are natural number.
Preferably, the predetermined pattern is defined to detect the last frame in a sector, and a counter is provided to reset the frame number to be output when the last frame is detected and to increment it otherwise.
An apparatus for reproducing signals from an optical disk according to the invention comprises an optical pickup which detects a light reflected from an optical disk, a reproducing device which reproduces digital data from the reflected light, and a decoder which decodes the digital data. The decoder comprises the above-mentioned apparatus for detecting a frame number.
An advantage of the present invention is that even when the bit length of the pattern of synchronizing signals is short and the distance between codes from the synchronizing signal representing another frame is short, the frame number can be output stably without erroneous detection.
REFERENCES:
patent: 4620300 (1986-10-01), Ogawa
patent: 5572496 (1996-11-01), Hayashi et al.
patent: 8-289249 (1996-11-01), None
patent: 10-27428 (1998-01-01), None
Deguchi Hironori
Usui Makoto
Huber Paul W.
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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