Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Reexamination Certificate
2001-02-07
2004-06-15
Decady, Albert (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
C714S769000, C714S755000, C369S059250
Reexamination Certificate
active
06751771
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for decoding data stored on a mass storage medium, for example an optical storage disk that stores data in a DVD-ROM format.
2. Description of the Related Art
DVD-ROM (digital versatile disk, read only memory) is for many applications a successor product to the CD-ROM format popularly used for recording and distributing data. A single-side, single-layer DVD-ROM disk can hold up to 4.7 GB (gigabytes) of data, or about seven times the capacity of the conventional CD-ROM. The high storage capacity of DVD-ROM is achieved in part by recording data as smaller pits along narrower tracks, as compared to the way that data are stored on CD-ROM disks. DVD-ROM also achieves higher capacity as compared to CD-ROM by using a more efficient sector data encoding scheme. The data format and the data encoding scheme for DVD-ROM disks are considerably different and more complex than those used for CD-ROM disks. As such, data processing and error decoding functions are different for the newer DVD-ROM format.
Data processing and error decoding functions have been refined over the course of many years for CD-ROM devices. An example of the highly optimized data processing and decoding of CD-ROM data is illustrated in U.S. Pat. No. 6,003,151, which describes partially concurrent error detection and Reed-Solomon error correction for CD-ROM data. The techniques described in this patent provide incremental but significant improvements in data processing rates. Various other optimized data processing strategies are implemented to facilitate the high speed reading and processing of data from CD-ROM disks. Consequently, when DVD-ROM was initially introduced as a data storage medium, the highly refined CD-ROM processing and decoding techniques allowed CD-ROM devices to have significantly better data access times than the less refined and newer DVD-ROM devices. This initial performance disparity slowed the adoption of the DVD-ROM storage format. As such, there was and there continues to be a need to improve the processing and decoding of DVD-ROM data. Thus, while the error decoding schemes for DVD-ROMs are different and considerably more complex than those used for CD-ROM disks, aspects of the concurrent error detection and error correction schemes described in U.S. Pat. No. 6,003,151 conceivably might improve sector processing speed and capability for DVD-ROM drives.
Decoding DVD-ROM disks requires knowledge of the data encoding on the disk.
The DVD-ROM sector-encoding flow consequently is described to provide a background for understanding the improvements of the present invention. The encoding and decoding of CD-DA and CD-ROM data are described first for comparison purposes.
The original compact disk standard was promulgated and eventually adopted for the distribution of digitized audio. The resulting specification is called the Red Book (ICE
908
) and the data storage medium was called CD-DA, for compact disk-digital audio. Two layers of error correction codes, identified as C
1
and C
2
in IEC
908
and ISO/IEC
10149
, are encoded with the audio data on CD-DA. When such a disk is played back, the pits on the surface of the disk are sensed by a laser pickup head and converted to a serial bit stream. The bit stream is then demodulated and split to thirty-two byte frames that are processed by a C
1
error corrector. The C
1
error correction codes are (
32
,
28
) Reed-Solomon codes over the Galois field GF(
2
8
) and can typically correct two errors in each frame. After the C
1
corrections, the four C
1
parity bytes are discarded, the other twenty-eight bytes in the frame are de-interleaved for the first time and the bytes are sent to the C
2
error corrector. This first de-interleaving mixes data bytes from two adjacent C
1
-corrected frames to form the twenty-eight byte input to the C
2
error corrector. The C
2
error correction codes are (
28
,
24
) Reed-Solomon codes over GF(
2
8
) and can typically correct two errors in each frame. After C
2
error correction, the four C
2
parity bytes are discarded and the remaining twenty-four bytes are de-interleaved for a second time. The second de-interleaving mixes data bytes from twenty-four different C
2
frames to generate twenty-four bytes of audio data, organized as six couples of sixteen-bit left-channel and sixteen-bit right-channel digital audio data.
C
1
and C
2
error corrections reduce the error rates of the digital audio data read from a disk. Furthermore, the data bit exchange accomplished in the first and second de-interleaving processes improves the playability of defective disks. When a scratch on a disk surface introduces a burst of errors, the erroneous data are de-interleaved into many different frames, thus reducing the number of errors per frame and increasing the probability of successful error corrections. On the other hand, the inclusion of parity bytes for two layers of error correction codes greatly reduces the amount of data that can be stored on a disk.
When a compact disk is used as a digital data storage medium, generally the data are stored in the CD-ROM format, which adds a third layer of Reed-Solomon error correction codes to the CD-DA data formatting to ensure the integrity of data read from the CD-ROM disk. This third layer of error correction codes, sometimes called C
3
, is applied to 2352 byte frames (or sectors) extracted from the C
1
-and C
2
-corrected and twice de-interleaved data stream. Note that the 2352 byte frame is different from the thirty-two byte and twenty-eight byte frames to which the C
1
and C
2
layers of error correction codes are applied. In some documents, including ISO/IEC-10149, the C
1
or C
2
frame is called the small frame.
C
3
is a Reed-Solomon product-like code (RSPC), as is described in ISO/IEC-10149 and in U.S. Pat. No. 6,003,151. A thirty-two bit error detection code (EDC) is also encoded in CD-ROM sectors to provide a further data integrity check, generally in the form of a cyclic redundancy code. The utilization of C
3
and EDC encoding further limits the capacity of digital data that can be stored on a CD-ROM. As a matter of fact, to record 2048 bytes (16384 bits) of user data according to the CD-ROM format, 57624 channel bits are stored on the surface of a CD-ROM.
DVD-ROM is a general-purpose data storage medium. Unlike the CD-ROM format, which may store data in a variety of sector formats, e.g., Mode
1
and Mode
2
Form
1
, the DVD-ROM format stores data in only one sector format. Each DVD-ROM data sector consists of 2048 bytes of main data (similar to the user data in a CD-ROM sector), twelve bytes of identification data (ID) and other header data, and four bytes of error detection code data (EDC).
FIG. 1
shows the data sector configuration for a DVD-ROM disk.
The four-byte identification data (ID) contains attributes and the physical address of the DVD-ROM sector. The bits of the identification data and the ID error detection code (IED) together form a (
6
,
4
) Reed-Solomon code, which is decoded to detect as well as to correct errors in the important ID data. The six-byte copyright management information (CPR-MAI) provides data for copyright protection and region management. The error detection code (EDC) is a four-byte cyclic redundancy check code attached to the 2060 bytes of ID, IED, CPR_MAI and main data before scrambling. Calculation of the EDC for each 2060 byte codeword is conventional and can be illustrated as follows. Suppose the MSB of the first byte of ID is b
16511
and the LSB of the last byte of the EDC is b
0
, then the EDC code word is selected so that the polynomial
I
(
x
)=
b
16511
x
16511
+ . . . +b
2
x
2
+b
1
x+b
0
(1)
is evenly divisible by the polynomial g(
x
)=x
32
+x
31
+x
4+
1. The four-bytes of EDC data are determined separately for each EDC codeword to cause the polynomial assembled according to Equation 1 to be evenly divisible by this check polynomial g(x). Note that the
Chuang Cheng-Te
Huang Eric
Britt Cynthia
De'cady Albert
Hogan & Hartson L.L.P.
MediaTek Inc.
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