Dynamic information storage or retrieval – Information location or remote operator actuated control – Selective addressing of storage medium
Reexamination Certificate
2001-12-14
2003-09-09
Neyzari, Ali (Department: 2655)
Dynamic information storage or retrieval
Information location or remote operator actuated control
Selective addressing of storage medium
C369S030040, C386S349000
Reexamination Certificate
active
06618331
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method and apparatus for accessing target data in a data storage medium, more particularly to a method and apparatus for facilitating fast and accurate access of target data in a data storage medium.
2. Description of the Related Art
When reading a data sector of an optical disk, it is necessary for an optical drive to verify whether the data sector is indeed the target sector of the optical disk in order to avoid decoding of unwanted data. However, because the header field of a data sector might include some errors that are introduced during stamping of the optical disk or that are due to other factors, and/or because the header field of the target sector might erroneously contain the identification data (ID) of another data sector, the optical drive has to repeat the search for the target sector when an initially-found data sector is deemed to be incorrect after decoding of the latter has begun. Therefore, there is always a need to provide a method and apparatus for facilitating fast and accurate access of target data in data storage mediums.
Referring to
FIG. 1
, a conventional digital versatile disk (DVD) player
1
is shown to comprise a pick-up head
100
, a demodulator
11
, a data buffer
12
, an error correction code (ECC) decoder
13
, a descrambler and error detection code (EDC) checker
14
, and an advanced technology attachment packet interface (ATAPI)
15
. During data access, when the DVD player
1
searches for a target sector of an optical disk
10
, the DVD player
1
initially performs a long-distance search so as to permit fast movement of the pick-up head
100
to the vicinity of the target sector. Thereafter, the DVDplayer
1
performs a short-distance search to locate the target sector. During the short-distance search, data at the vicinity of the target sector (hereinafter referred to as a nearby sector) is read by the pick-up head
100
and is sent to the demodulator
11
. The demodulator
11
validates identification data (ID) of the nearby sector against an identification error detection (IED) code of the nearby sector. After successfully validating the identification data of the nearby sector, the pick-up head
100
is enabled to find the target sector by calculating the distance from the nearby sector to the target sector. Once the target sector has been located, data is read in sequence starting from the target sector, and the demodulated data is stored in the data buffer
12
to form an error correction code (ECC) block
16
. Aside from a main data portion
161
, the ECC block
16
further includes an inner-code parity (PI)
162
and an outer-code parity (PO)
163
. The ECC block
16
thus formed in the data buffer
12
is then sent to the ECC decoder
13
for decoding of the data and for finding errors in the accessed data.
In the conventional DVD player
1
of
FIG. 1
, when the identification data of another data sector erroneously contains that of a target sector (or a nearby sector adjacent to the target sector), and when the error was not detected by the demodulator
11
, the DVD player
1
will likely locate an incorrect target sector. Therefore, when the ECC block
16
is sent to the ECC decoder
13
for data decoding, since inner-code parity (PI) and outer-code parity (PO) checking will be performed, detection of the incorrect target sector can be discovered by the ECC decoder
13
so that the search for the target sector can be repeated anew. However, under such circumstances, since the new search for the target sector can only start after the ECC block
16
has formed in the data buffer
12
and the ECC decoder
13
has begun the decoding procedure for the ECC block
16
, reduced efficiency and increased idle time result.
SUMMARY OF THE INVENTION
Therefore, the main object of the present invention is to provide a method and apparatus for facilitating fast and accurate access of target data in a data storage medium.
According to one aspect of the invention, there is provided a method for accessing target data in a data storage medium having sequentially arranged data sectors recorded therein. Each of the data sectors contains at least identification data, an identification error detection code and main data. The method comprises:
(a) reading one of the data sectors recorded in the data storage medium;
(b) demodulating said one of the data sectors to generate a block unit that contains the identification data, the identification error detection code and the main data of said one of the data sectors, and that further contains an inner-code parity for the block unit;
(c) verifying accuracy of the identification data in the block unit;
(d) repeating steps (a) , (b) and (c) for a succeeding one of the data sectors of the data storage medium when the identification data in the block unit is found to be inaccurate;
(e) finding a target data sector that corresponds to starting location of the target data in the data storage medium with reference to the block unit having accurate identification data;
(f) reading the data sectors recorded in the data storage medium in sequence starting from the target data sector;
(g) demodulating the data sectors read in step (f) to generate the block units that correspond thereto;
(h) storing the block units generated in step (g) in a data buffer to form a block; and
(i) decoding the block formed in the data buffer.
According to another aspect of the invention, there is provided an apparatus for accessing target data in a data storage medium having sequentially arranged data sectors recorded therein. Each of the data sectors contains at least identification data, an identification error detection code and main data. The apparatus comprises:
a pick-up head adapted for reading one of the data sectors recorded in the data storage medium;
a demodulator coupled to the pick-up head and operable so as to demodulate said one of the data sectors to generate a block unit that contains the identification data, the identification error detection code and the main data of said one of the data sectors, and that further contains an inner-code parity for the block unit;
an error correction code decoder coupled to the demodulator and operable so as to verify accuracy of the identification data in the block unit, the error correction code decoder enabling the demodulator to generate the block unit for a succeeding one of the data sectors recorded in the data storage medium when the identification data in the block unit for a current one of the data sectors is found to be inaccurate;
the demodulator being under the control of the error correction code decoder to enable the pick-up head to find a target data sector that corresponds to starting location of the target data in the data storage medium with reference to the block unit having accurate identification data, and to read the data sectors recorded in the data storage medium in sequence starting from the target data sector;
the demodulator demodulating the data sectors from the pick-up head to generate the corresponding block units; and
a data buffer coupled to the demodulator for storing the block units generated thereby to form a block in the data buffer;
the error correction code decoder being further coupled to the data buffer and being further operable so as to decode the block formed in the data buffer.
REFERENCES:
patent: 6108281 (2000-08-01), Tozaki et al.
patent: 6181660 (2001-01-01), Hirayama et al.
Knobbe Martens Olson & Bear LLP
Neyzari Ali
LandOfFree
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