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1. WO2007000707 - A METHOD AND SYSTEM FOR PROTECTING DATA STORED ON AN OPTICAL DISC

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

A METHO AND SYSTEM FOR PROTECTING DATA STORED ON AN
OPTICAL DISC

FIELD OF THE INVENTION
The invention relates to a method and system for protecting data stored on an optical disc.

BACKGROUND OF THE INVENTION
With the developing of optical disc industry and the increasing of storage capacity such optical discs can store, a long time storage is more and more needed. For example, optical discs may correspond to a DVD (digital versatile disc), VCD (video compact disc), or BD (Blu-ray disc).
Guarantying a long term storage is of course related to the quality of the optical disc since if the quality of an optical disc is not very good, or the performance of an optical disc has degraded over time, the recorded data might be lost. The degrading of the optical disc may for example be caused by scratches, dust particles, tilt. Furthermore, the problem of losing data is especially relevant in the last generations of optical discs, such as 16X, DL for DVD.
Unfortunately, users cannot be aware of the optical disc state, and thus cannot take any actions to protect the data.

OBJECT AND SUMMARY OF THE INVENTION
It is an object of the invention to provide a secure method and system for protecting data of an optical disc.

According to a first solution, the method according to the invention comprises the steps of:
- replicating the data of said optical disc to a first storage device,
- reading out the data from said optical disc,
- generating, from a quality parameter of the read out data, an output signal indicating a good or low quality of said optical disc, and
- writing the data of said first storage device to a second storage device if said output signal indicates a low quality.

According to a second solution, the method of the invention comprise the steps of:
- reading out the data from said optical disc,
- generating, from a quality parameter of the read out data, an output signal indicating a good or low quality of said optical disc, and
- writing the data of said optical disc to a storage device, if said output signal indicates a low quality.

The advantage of this method is that it allows to write data from the optical disc to another storage device before data of said optical disc cannot be read. In other words, data are saved in anticipating and detecting a possible crash of the optical disc.
The first solution is advantageous because data are systematically first replicated on the first storage device, independently of the optical disc state. The writing of data to another storage device is only done after detection of a low optical disc quality, resulting in a very safe solution.
The second solution is advantageous because no systematic data replication on the first storage device is done, and the writing of data to another storage device is only done after detection of a low optical disc quality.

The invention also proposes a system comprising processing means for implementing the various steps of said method.

BRIEF DESCRIPTION OF THE DRAWINGS
These and other aspects of the method and system for protecting data of an optical disc, according to the invention will become apparent from and will be elucidated with respect to the implementations and embodiments described hereinafter and with reference to the accompanying drawings, wherein:
Fig. 1 is a first flow chart diagram depicting the method of protecting data of an optical disc according to the invention;
Fig. 2 is a second flow chart diagram depicting the method of protecting data of an optical disc according to the invention;
Fig. 3 is a schematic block diagram illustrating one embodiment of a system to protect data of an optical disc according to the invention.

Same reference numerals are used to denote similar parts throughout the figures.

DETAILED DESCRIPTION OF THE INVENTION
Fig. 1 is a first flow chart diagram depicting the method of protecting data of an optical disc according to the invention. The method according to the invention comprises the steps of:
- Replicating (101) the data of the optical disc to a first storage device. The first storage device may be a HDD (Hard Disc Drive), or temporary
storages device such as a RAM memory.
- Reading out (102) the data from the optical disc. Data which are read out may be outputted to a display device, after decoding (if needed), and after correction (if needed) of some errors. The errors may, for example, be
caused by scratches, dust particles, tilt, fingerprint. The data of the optical disc may, for example, be coded according to the MPEG (Moving Picture Expert Group) or JPEG (Joint Picture Expert Group) standard. Error
correction may be done according to an ECC (Error Correction Code)
algorithm, such as Reed-Solomon Code.
- Generating (103), from a quality parameter of the read out data, an output signal indicating a good or low quality of said optical disc. The quality
parameter may be an error rate, and/or error length, and/or jitter, or and/or tilt. The quality parameter reflects the quality of the optical disc. The
number of errors used to calculate the error rate may include corrected
errors and not corrected errors.
- Writing (104) the data of the first storage device to a second storage device if said output signal indicates a low quality, so that the data of the optical disc are duplicated and protected securely on the second storage device.
The second storage may be another optical disc (recordable), a magnetic disc, or a memory. If the output signal indicates good quality, then the
process may do nothing for the optical disc.

The error rate is the number of wrong decoded bits/total number of read bits of the data, such as 3*10"4.

The error length is the total length of errors in the read bits. Because some errors are not distributed randomly over the optical disc, but are occurring in consecutive ECC blocks, it may be necessary to use error length to valuate the quality of the optical disc. The length of the errors may exceed a length threshold, e.g. 25 ECC blocks.
The jitter is a difference between a set length and an actual length of each pit or land. In the optical disc standard specifications, a maximum disc jitter is specified, such as BD case, its maximum is 6.5%.
The tilt is the incline of an optical disc along the radial or tangential direction. In optical disc standard, a tilt range is specified, such as [-0.5°, 0.5°].

The generating step (103) may generate the output signal according to three different strategies:

Strategy 1:
(a) evaluating a quality value of the optical disc from a quality parameter of the read out data. If the quality value is higher, the quality of the optical disc is better.

Otherwise, if the quality of the optical disc is lower, the optical disc cannot keep the data for a longer time, meaning that the optical disc is about to crash. The evaluating step comprises:
- calculating the error rate, and/or an error length, and/or a jitter value, and/or a tilt value, for generating the quality parameter.
- determining via a lookup table the quality value (e.g. in the range [0, 100]) from the quality parameter. For example, in the table 1 below, for an error rate being in the range of l*10~2~5*10~2, a quality value of 50 is determined. The lookup table may be predetermined, for example, by an optical disc supplier, recorder supplier, disc player supplier.




Table 1 : Look-up table Error rate/ Quality value



Table 2 : Look-up table Error length / Quality value



Table 3 : Look-up table Jitter / Quality value


Table 4 : Look-up table Tilt / Quality value

The quality value may also be determined according to a histogram of error rate, error length, jitter, or tilt, which also can be pre -predetermined by a supplier of recorder or optical disc.

(b) comparing the quality value with a quality threshold, for generating the output signal. For example, when the quality value is below the quality threshold, it means that the data of the optical disc are about to be lost, and the output signal indicates a low quality of the optical disc. Alternatively, if the quality value is above the quality threshold, it means that the optical disc can still keep the data in a safe way, and the output signal indicates a good quality of the optical disc.
The quality threshold may be pre-predetermined by a supplier of the optical disc, recorder, player etc. For example, with quality threshold of 60, and a quality value of 50, the quality of the optical disc is considered low, which is reflected by the output signal.

Strategy 2:
(a) evaluating a quality value of the optical disc from a quality parameter of the read out data. The detailed process to evaluate a quality value of the optical disc is the same as that explained in the strategy 1.
(b) comparing the quality value with a previously stored quality value, for generating said output signal. The previous quality value was saved in a HDD or other memory in a previous time. If the quality value is not too much below the previous quality value, the output signal indicates the quality of the optical disc is good quality. If the quality value is much lower than the previous quality value, the output signal indicates the quality of the optical disc is low quality.
(c) saving the quality value evaluated in the current time to the HDD for next quality evaluation.

Strategy 3:
(a) evaluating a quality value of said optical disc from a quality parameter of the read out data. The detailed process to evaluate a quality value of the optical disc is the same as that explained in the strategy 1.

(b) obtaining a set of history quality values of the optical disc. The set of history quality values are stored in the HDD or other memory. The set of history quality values were evaluated before this current time.
(c) evaluating a lifetime of said optical disc from said set of history quality values and the quality value evaluated in the current time. The lifetime indicates how long the data can be kept in the optical disc securely. For example, the lifetime can be evaluated in calculating the slope of the curve representing the quality values along the time. The lifetime may be, for example, 0.5 year, 1 year, 5 years, 10 years.
(d) comparing the lifetime with a lifetime threshold, for generating said output signal. The lifetime threshold may be provided by a supplier of optical disc, player, recorder. If the lifetime is shorter than the lifetime threshold, the output signal indicates a low quality of the optical disc, meaning that the data of the optical are about to be lost. Alternatively, if the output signal indicates a good quality, the data of the optical can be kept in the optical disc for still a long time.
(e) saving the quality value evaluated in the current time, to be used in the next history quality values.

Fig. 2 is a second flow chart diagram depicting the method of protecting data of an optical disc according to the invention. The method comprises the steps of:
- Reading (201) out the data from said optical disc: data are read according to the needs of the application.
- Generating (202), from a quality parameter of the read out data, an output signal indicating a good or low quality of said optical disc. The detailed
procedure is same as explained for the method according to Fig.l.
- Writing (203) the data of said optical disc to a storage device, if said output signal indicates a low quality. This step is intended to write data stored on the optical disc as soon as the quality of the optical disc is considered low, meaning that the optical disc is about to crash. The storage device can be another optical disc (recordable), a magnetic disc, or a memory with good quality.

Fig. 3 is a schematic block diagram illustrating one embodiment of a system 300 to protect data of an optical disc 310 according to the invention. The system 300 may be a recorder, player, computer etc.
The system 300 comprises reading means 301 for reading out the data from the optical disc 310. The reading means may correspond to an optical pickup unit (OPU).

The data stored in the optical disc 310 may be coded, for example, according to the MPEG or JPEG standard. If the data are coded, a decoder 302 is used to decode the data read out from the optical disc 310. If the data are coded according to the MPEG standard, the decoder 302 is a MPEG decoder. Alternatively, if the data are coded according to JPEG standard, the decoder 302 is a JPEG decoder.
An ECC circuit 303 is used to correct errors, if any, of the decoded data. The ECC may be Reed-Solomon Code. The data coming from the ECC circuit 303 may be outputted to a display device by outputting means 304. The outputting means 304 may correspond to a buffer or an output image/video driver. Of course, if read out data are just intended to be used internally in the system 300, the outputting means 304 can be omitted.
The system 300 also comprises generating means 305 for generating, from a quality parameter of the read out data, an output signal OS indicating a good or low quality of said optical disc. As explained previously, the quality parameter reflects quality of the optical disc. The generating means may correspond to an error rate counter, and/ or error length counter, and/or jitter calculator, and/or tilt calculator.
The system 300 further comprises replicating means 306 for replicating the data of the optical disc 310 to a first storage device 307, such as a HDD, and writing means 308 for writing the data from the first storage device 307 to a second storage device 309, such as a recordable optical disc. Of course, the apparatus in charge of reading data of optical disc 310 can also be used as data recorder, in inserting a new recordable optical disc. If the second storage device 309 corresponds to an optical disc, then the writing means 308 may include a driver to drive optical disc 309 and optical disc 310. The second storage device 309 can also correspond to a hard disk, a magnetic disc, or a memory.
If the first solution according to Fig.l is implemented, data of the optical disc 310 are first replicated on the first storage device 307, via the use of the reading means 301, decoding means 302 and ECC circuit 303. Then, if the output signal OS indicates a low quality of the optical disc 310, this output signal OS is used as an input signal by the writing means 308 for starting writing data on the second storage device 309.

If the second solution according to Fig.2 is implemented, data of the optical disc are replicated on the first storage device 307, via the use of the reading means 301, decoding means 302 and ECC circuit 303, only if the output signal OS indicates a low quality of the optical disc 310. In this case, the output signal OS is used as an input signal by the writing means 308 for starting writing data on the second storage device 309.
The generating means 305 may comprise:
(a) evaluating means for evaluating a quality value of said optical disc from a quality parameter of the read out data, or a lifetime of said optical disc from a set of history quality values and the quality value evaluated in the current time. The evaluating means may comprise calculating means for calculating the error rate, and/or an error length, and/or a jitter value, and/or a tilt value, for generating the quality parameter, and determining means for determining via a lookup table said quality value from said quality parameter.
(b) obtaining means for obtaining the set of the history quality value to the evaluating means so as to combine with the current quality value to evaluate the lifetime as mentioned above. For example, a memory can be used to obtain the set of the history quality value.
(c) comparing means are used to compare the quality value with a quality threshold, or comparing the quality value with a previously stored quality value, or comparing the lifetime with a lifetime threshold, for generating the output signal OS. For example, if the quality value is lower than the quality threshold that means the data of the optical disc might be lost, and the output signal indicates a low quality of the optical disc. Alternatively, if the quality value is above the quality threshold that means that the optical disc can still keep the data in a safe way, and the output signal indicates a good quality of the optical disc. When the quality value is much below the previously stored quality value, the output signal indicates a low quality of the optical disc. When the lifetime is shorter than the lifetime threshold, the output signal indicates a low quality of the optical disc, and the data of the optical might be lost. Alternatively, if the output signal indicates a good quality of the optical disc, the data of the optical can be kept in the optical for still a long time.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be constructed as limiting the claim. The word 'comprising' does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several distinct elements and by means of a suitable programmed computer. In the unit claims enumerating several means, several of these means can be embodied by one and the same item of hardware. The usage of the words first, second and third, etcetera do not indicate any ordering. These words are to be interpreted as names.