System and method for selectively recovering areas on a disc marked as unuseable

[0002] This invention relates to memory storage systems and methods and more particularly to a system and method for controlling the storage of data in the memory taking into account disc trouble spots.

[0003] Presently, if memory, such as a CD, DVD or hard drive, detects a severe reading error at a particular location in the memory, it informs the host software and the host software will not use that spot again. The host remaps the memory to an alternate location as controlled by its sparing table marking the spot as bad. The memory then places new data that would have been directed to the trouble location in its sparing table. When it is desired to read data from the spot that is bad, instead of reading that spot, the memory will read the data stored at a specific area in the sparing table.

[0004] Thus, if there is a fingerprint or smudge or something on the disc, or if the disc is scratched or worn at a spot, the disc marks the trouble area as a bad area and then rewrites the data from that area to a new area. Two different situations can occur. One is contamination or errors that are temporary are those that may be removed by cleaning the disc or by doing something to the disc; and the other is a permanent defect like a scratch or the wearout mechanism of the disc that is not recoverable. Current systems treat these two cases identically since they cannot tell the difference between a fingerprint, a piece of dust, a scratch, or the wearing out of a piece of the media. In either case, the memory tells the software that it had trouble reading a particular spot and directs the software to map that spot as bad. Thus, once a spot is marked as bad it is never reused, even if, for instance, the disc is cleaned and the smudge is removed.

[0005] These and other objects, features and technical advantages are achieved by a system and method which in one embodiment takes advantage of the fact that all of the areas on the disc that are marked as bad are located in the sparing table. The system can then look at the disc and see what kind of errors occurred by mapping data back onto the disc and using pattern recognition to detect what kinds of errors they are. If it is determined that an error is recoverable, such as a fingerprint or a dust error, the user will be directed to clean the disc or other methods may be used to remove the problem. Once the disc has been cleaned, the system can check that spot to see if it is good, and if good, relocate the data back out to that previously marked bad spot. The system re-references the disc so that it points again to the trouble spot and not to the sparing table.

[0006] One of the problems that could occur with this system is that, over time, the section of data pertaining to the trouble spot may have been reused. This could occur if the data in the sparing table is changed (by update from the user) without changing the data on the disc at the spot that has been marked as bad. For example, suppose a text file is written to a disc, and a fingerprint exists on the disc at a location that is in the middle of the text file. The first one-third of the text file and the last one-third is okay as is, but the data stored at the middle one-third is difficult to read. The middle one-third of the data is then given to the computer, which acknowledges that there indeed was trouble reading that data. The computer will then take the middle one-third of the text file and place it into the sparing table. Note that now the same data resides at the trouble spot on the disc as well as in the sparing table. Whenever that text file is desired, the beginning one-third will come off the disc from the location where it normally comes from. The middle one-third of the text file will come from the sparing table (and not from its normal spot on the disc) and the last one-third will come from its original location. This data is then edited by the user, who may not even know that the memory had a problem. When the changed data goes back to the disc, the first one-third overwrites the previously saved first one-third, the middle part is written to the sparing table, and the last one-third goes back to where it was originally. The trouble spot data is not touched. Thus, the most recent copy of the middle one-third would be in the sparing table so the disc could not just be cleaned and the middle part of the disc used immediately because it could have different data from what is in the sparing table.

[0007] To fix this problem, data corresponding to trouble spots that are now good is read from the sparing table to the disc.

[0008] The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.

[0009] For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0010] FIG. 1 shows a flow chart of system error determination; and

[0011] FIG. 2 shows a flow chart of system disc corrections.

[0012] Turning now to FIG. 1, box 101 operating in conjunction with a general purpose computer, such as a PC, will, based on previous experience, know the typical pattern of a dirt speck, dust or scratch. Typically, scratches, dirt speck, dust, fingerprints, disc wearout and media defects will all provide unique patterns.

[0013] Pattern recognition will be done by software in the computer which will access the data on the sparing table and virtually map onto the disc. Then a software program looks at this virtual disc with these marks on it and analyzes the marks to correspond them to dirt, scratches, fingerprints, etc.

[0014] Typically, the sparing table is not very big. If a file is in error, the system does not have enough space to put that whole file into the sparing table. It will only spare out a frame or a sector. The system does not look at the whole disc since scanning a whole disc takes a considerable amount of time looking for bad spots. Since that work has already been done and the results put into the sparing table, the system only need review the sparing table. A refinement is that once a certain set of data has been determined to correspond to an unfixable trouble location, that set of data no longer need be looked at. From a time point of view, it is quick because it only has to read and analyze the sparing table.

[0015] Additional, if time permits the whole disc can be verified with a lower thushold for errors that would be set to spare the data. This way dirt, smudges and fingerprints could be detected before they cause a problem.

[0016] From the trouble data the pattern recognition would determine if there is a long continuous pattern of connecting locations on the disc so that it would be like a scratch, or whether it is a small area that is a close cluster like a piece of dirt. A fingerprint would be something that would be similar to a series of small scratches that are circular in nature. Disc wearout will either happen at a single spot, or it will happen along the groove. It is highly unlikely that any type of contamination will follow a single groove precisely. That is virtually impossible because it is so small.

[0017] Box 106 controls this function, and if there are not fixable errors, the system is finished, box 107. If fixable errors are determined, locations are marked, box 108, and the user is asked to take some action, box 109.

[0018] With a wearout, the system does not tell the user anything since there is nothing he/she can do about it. On a scratch, it is highly likely that the system will tell the user anything since asking most users to repair a scratch could cause a lot more damage than the scratch itself. However, for diagnostic reasons, both types of information can be made available if desired. If the errors become significant enough, the system asks the user to move data from the damaged disc to a different disc.

[0019] FIG. 2 shows the situation where the disc has been cleaned, box 210, and reinserted back into the computer, or VCR, MiniDisk or DVD player, or other device. Box 211 runs an error check of the disc to see which locations are still bad. Assuming that all locations which had been identified as fixable are now showing “good” data, the newly read data is ignored and the latest disc located in the storing table is read into the corresponding location on the disc, via box 213 and box 214. Those trouble locations are removed from the trouble index.

[0020] If only some of the trouble spots have been fixed, only data corresponding to those “fixed” spots are read back to the disc.

[0021] Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.