Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Reexamination Certificate
1998-10-22
2001-07-17
Psitos, Aristotelis M. (Department: 2651)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
C369S047280, C360S051000, C386S349000, C717S152000
Reexamination Certificate
active
06263469
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the field of Digital Versatile Disks, or DVD. More particularly, the present invention relates to methods and apparatuses for reducing the data access time from a digital storage medium, such as a DVD Read Only Memory (hereafter, DVD-ROM) or a recordable DVD (hereafter referred to generically as DVD-Random Access Memory or DVD-RAM).
2. Description of the Related Art
A sector in a DVD is variously called a data sector, a recording sector or a physical sector, depending upon its configuration.
FIG. 1
shows a data sector of a DVD disk. As shown in
FIG. 1
, a data sector includes 2048 bits of data, 4 bytes of identification (ID) data; 2 bytes of ID Error Detection code (IED), 6 bytes of Copyright Management Information (CPR MAI) and 4 bytes of Error Detection Code (EDC). The 2048 bytes of data are then scrambled, using a feedback shift register. An ECC block is made up of 16 of the data sectors shown in FIG.
1
. The 16 data sectors of the ECC block are then encoded, using Cross-Interleaved Reed-Solomon Code (CIRSC). An ECC block, including outer code parity (PO) and inner code parity (PI), is shown in FIG.
2
. As shown in
FIG. 2
, 10 bytes of PI are added after each row, and one row of 182 bytes of PO are added after each of the 16 data sector of the ECC block, for a total of 16 rows of 182 bytes of PO data.
A recording sector is formed by interleaving the PO data in each of the 16 data sectors. One such recording sector is shown in FIG.
3
. Each recording sector, therefore, includes a data sector consisting of 12 rows of 172 bites, each row having 10 bytes of PI data appended thereto. One row of 182 bytes of PO data is also included, as a result of the interleaving process referred to above.
Finally, a physical sector, according to the DVD specification, is formed by a two step process. First, an 8:16 modulation conversion is carried out, which effectively doubles the width of each sector. Then, 32 bits of frame synchronization information are prepended to each of the recording sectors in each row. A physical sector is shown in FIG.
4
. As shown therein, each Sync Frame includes
4
bytes of synchronization information, each indicating the start of a recording sector, each recording sector consisting of 1456 bits, or 172 bytes of data and 10 bytes of PI information. Each synchronization code (hereafter“sync pattern” ) SYN
0
to SYN
7
is selected according to sync tables, not shown.
To access (e.g., to read or write) data from a DVD-ROM or DVD-RAM, a DVD read or read/write device must find the beginning of each physical sector. As shown in
FIG. 4
, only a single SYN
0
bit pattern is included in each physical sector. To find the beginning of a physical sector, therefore, requires the DVD device to find the SYN
0
bit pattern. It however, the disk has been somehow damaged or random noise has prevented the device from identifying the SYN
0
pattern, the DVD-ROM/RAM device may be unable to locate the SYN
0
bit pattern and thus will not be able to identify the beginning of a physical sector. The DVD device must then backtrack and attempt to read the physical sector again, by again attempting to detect the singular SYN
0
bit pattern marking the beginning of each physical sector. This procedure may be repeated for a predetermined number of attempts before the SYN
0
bit pattern is detected. Each time, the DVD-ROM/RAM device must traverse all 38,688 channel bits of the physical sector before backtracking to attempt detection of the SYN
0
pattern again. This repeated traversal of the physical sector and repeated scan for the unique and singular SYN
0
pattern necessarily increases the data access time of such DVD ROM/RAM devices. Moreover, if the disk is damaged and the SYN
0
bit pattern is unreadable, the physical sector including the damaged SYN
0
pattern will be unreadable, potentially rendering the data or program stored on the DVD-RAM or ROM inaccessible and the disk useless.
What are needed, therefore, are devices and methods to reduce the access time of data from DVD-ROM and DVD-RAM disks. What are also needed are devices and methods to reduce the data access time of DVD-ROM and DVD-RAM disks, as well as methods and devices that are tolerant of some manufacturing defects and/or to the effects random noise, particularly in the disk areas reserved for the physical sector synchronization patterns.
SUMMARY OF THE INVENTION
The principles of the present invention provide for devices and methods to reduce the access time of data from DVD-ROM and DVD-RAM disks. The principles of the present invention also provide for devices and methods to reduce the data access time of DVD-ROM and DVD-RAM that are tolerant of some manufacturing defects and/or to the effects random noise, particularly in the disk areas reserved for the physical sector synchronization patterns.
In accordance with the principles of the present invention and those that will be mentioned and will become apparent below, a method of accessing data from a digital storage medium configured to store data in sectors delimited by a predetermined sequence of sync patterns, comprises the steps of:
detecting a sync pattern within a sector of the storage medium;
determining whether the detected sync pattern matches an expected sync pattern;
generating a sync error signal when the detected sync pattern does not match the expected sync pattern;
returning to the detecting step as long as a number of sync error signals does not exceed a predetermined threshold.
According to other embodiments, the predetermined threshold may be programmable. A step of incrementing a sync error counter each time the sync error signal is generated may also be carried out. A step of resetting the sync error counter when the determining step determines that all detected sync patterns within the sector match the expected sync pattern may also be carried out. The method of the invention may include a step of resetting the sync error counter when the number of sync error signals generated exceeds the predetermined threshold. The method may also include the step of resetting the sync error counter when a sync pattern indicative of a beginning of a sector is detected. A step of generating an disk error signal when the number of sync error signals exceeds the predetermined threshold may also be carried out. A step of storing an ordered sequence of sync patterns corresponding to the sync patterns of a sector may also be carried out, each expected sync pattern being read in turn from the stored ordered sequence. The sector may be physical sector and the digital storage medium may be a DVD.
The present invention may also be viewed as an apparatus to access data from a digital recording medium configured to store data in sectors delimited by a predetermined sequence of sync patterns, comprising:
a sync pattern detector;
a sync sequence detector to detect whether a sequence of sync patterns detected by the sync pattern detector matches the predetermined sync pattern sequence, the sync sequence: detector generating a sync error signal whenever a detected sync pattern fails to match an expected sync pattern taken from the predetermined sync pattern sequence;
a sync error signal counter to count a number of sync error signals generated by the sync sequence detector, and
a comparator to compare a number of sync error signals counted by the sync error signal counter with a sync error threshold, the comparator generating a disk error signal when the threshold is exceeded.
According to other embodiments of the invention, the sync sequence detector may include a finite state machine. The finite state machine may be an X-state finite state machine, wherein X is the number of sync patterns in the predetermined sequence of sync patterns. The digital recording medium may be a DVD and the finite state machine may be a 26-state finite state machine. A logic circuit may be coupled to the sync sequence generator and/or the sync signal error counter, the logic circuit generating a sync error sig
Oak Technology, Inc.
Psitos Aristotelis M.
Young Law Firm P.C.
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