Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Reexamination Certificate
1999-03-05
2001-09-18
Decady, Albert (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
C714S769000
Reexamination Certificate
active
06292921
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a Reed-Solomon type error correction device and an optical reading apparatus comprising such a device. The invention applies in particular within the context of error correction in apparatuses for reading optical or magneto-optical disks.
The compact disc, generally abbreviated to ‘CD’, was introduced onto the market in 1982. Given the need for media of ever larger capacity and in order to take account of developments in the fields of the recording, coding and reading of data, a new standard has recently emerged. This is the so-called DVD standard. The latter relies, for reading, on similar principles to those of CD, but allows a greater density of information.
Compatibility of CD and DVD readers is obviously desirable for users. However, the coding of the data in the two standards is very different: CD and DVD data packets are of different length and use a different kind of interleaving, as well as different parameters for error correction.
Typically, in respect of Reed-Solomon type error correction, in order for a reading apparatus to be able to decode both the CD format and also the DVD format, two circuits, dedicated respectively to CD type error correction and to DVD type error correction would be used within the same apparatus.
It is obvious that this solution is not satisfactory, since redundant elements are employed, thereby raising the cost of the device. Moreover, given the difference in format of the DVD and CD type data packets to be processed, it is difficult to find a configuration which is satisfactory for both cases.
The invention consequently proposes a correction device which can perform the correction of both formats.
SUMMARY OF THE INVENTION
The subject of the invention is a Reed-Solomon error correction device, comprising Reed-Solomon type correction means for carrying out correction passes, characterized in that it furthermore comprises:
a first memory intended for containing DVD type data, as well as CD type data after a first correction pass, with a view to the deinterleaving of the said CD type data before a second correction pass;
a second memory of cache memory type and distinct from the said first memory, the said second memory being intended for containing CD type data before correction, as well as deinterleaved CD type data.
Two memories are therefore used, a first of relatively large size, making it possible to store the DVD type packets as well as the CD type packets after the first pass, and a second, of much smaller size, intended to be used solely during correction in CD mode. This has the advantage that during correction in CD mode, the first memory is called upon solely for the deinterleaving required. The frequency of access to this first memory is therefore reduced and allows the use of a lower-performance and hence cheaper memory. This is particularly beneficial when the first memory is a commercial circuit.
According to a particular embodiment, the symbols corresponding to the DVD type data are transmitted to the Reed-Solomon type correction means from the said first memory, whereas the symbols corresponding to the CD type data are transmitted to the Reed-Solomon type correction means from the said second memory.
The second memory is used to perform an on-the-fly correction for two reasons: firstly, being of small size, it is possible to use a memory of high performance from the frequency of access point of view; secondly, the CD type code-words lend themselves better to such correction than the DVD type code-words, which are much more voluminous.
According to one embodiment, the said device comprises a first integrated circuit containing the said Reed-Solomon correction means and the said second memory, whereas the said first memory is contained in a second integrated circuit distinct from the first integrated circuit.
The subject of the invention is also an optical disk reader comprising the correction device.
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Daoudi Mohamed
Isola Philippe
Paul Philippe
Viroulaud Christophe
Davenport Francis A.
De'cady Albert
Fried Harvey D.
Thomson Licensing S.A.
Torres Joseph D.
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