1. Field of the Invention
The invention relates to an optical disc drive, and more particularly, to an accessing method for processing and replacing defect management data stored in an optical disc when an optical disc drive reads the optical disc.
2. Description of the Prior Art
Since optical discs use tiny and concentrated marks to increase storage capacity, stains, dust or scratches can entirely cover these marks and affect the accuracy of reading. Optical disc drives provide defect management mechanisms such that data in defect areas can be stored in replacement areas on the optical disc. When an optical disc drive reads data from the optical disc, replacement data is substituted for the defect data and thus the optical disc can be read smoothly.
However, with regards to the conventional method of accessing defect management data, each time the optical disc drive reads data of a data block, the pick-up head must be moved to the defect management area—either the replacement area 1 located in an inner track or the replacement area 2 located in an outer track—to search and read required defect management data, and then the pick-up head is moved back to the data area to read data of a data block requested by the next command. As a consequence, when the optical disc drive reads an optical disc, the pick-up head is moved back and forth between the data area and defect management area, increasing reading time and thus lowering the overall performance of the optical disc drive. Therefore, the conventional optical disc drive still has unsolved problems in accessing defect management data on an optical disc.
One of the objectives of the present invention is to provide a method of accessing defect management data, which adds a data cache area to store hot defect management data, reads cached defect management data of the required data block, and expedites replacing data as well as correcting data of the required data block, thereby enhancing the reading efficiency.
Another objective of the present invention is to provide a method of accessing defect management data, which estimates characteristics of defect management data and sifts hot defect management data during accessing of defect management data, and stores the hot defect management data in the data cache area such that the number of times of moving a pick-up head back and forth can be reduced, thus decreasing the overall reading time.
To accomplish the aforementioned objectives, an optical disc drive receives a command to read data in the required data block on an optical disc, and stores the retrieved data in a first buffer area. The optical disc drive firstly reads cached defect management data of the required data block from a data cache area; otherwise, the optical disc drive reads defect management data of the required data block in a defect management area on the optical disc, stores the retrieved defect management data into a second buffer area, and then examines the defect management data in the second buffer area to see if the stored defect management data are hot defect management data. If the stored defect management data are hot defect management data, the optical disc drive copies the defect management data in the second buffer area to a data cache area, replaces defect data in the first buffer area with the defect management data, and outputs updated data of the required data block in the first buffer area.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
To illustrate the adopted techniques and achieved benefits of the present invention, preferred embodiments along with accompanying figures are detailed as below.
When an optical disc drive reads an optical disc, the method of accessing defect management data according to the present invention firstly allocates three buffer areas, here annotated as the first buffer area, second buffer area and third buffer area, in the memory of the optical disc drive. The first buffer area is used to store obtained data of a data block, and the second buffer area is used to store obtained defect management data. Apart from original storage function of the first and second buffer areas, a separately allocated third buffer area is used as a data cache buffer area to store hot defect management data. A standard of classifying hot defect management data includes the address of defect management data, type of defect management data, and the number of times of accessing defect management data. When the optical disc drive receives a command to read data of a data block on the optical disc, during the process of accessing the defect management data, the hot extent of the defect management data is also estimated, and the defect management data qualified as hot defect management data are then stored in the third buffer area.
Since only the data in the first and second buffer areas are rewritten each time an optical disc drive reads data of a data block, data in these two buffer areas are repeatedly deleted and updated. The third buffer area is separately allocated, data read from the optical disc will not be stored in the third buffer area directly, and thus the original storage state of the third buffer area is unaffected by data reading of the data block on the optical disc. Instead, after the defect management data qualified as hot defect management data are consequently stored into the third buffer area and appended to the original data stored in the third buffer area, the data amount of the hot defect management data is increased gradually.
When an optical disc drive receives a command, the optical disc drive reads data in the required data block on the optical disc, and stores the retrieved data in the first buffer area. Next, the optical disc drive searches the third buffer area for the defect management data of the data block. If the defect management data of the required data block are found, the optical disc drive uses the cached defect management data in the third buffer area to replace the defect data in the first buffer area immediately, and then outputs the replaced data in the first buffer area. Therefore, the reading time of defect management data can be reduced greatly. If the defect management data of the required data block cannot be found in the third buffer area, the optical disc drive reads the defect management data in the defect management area on the optical disc and stores the retrieved defect management data in the second buffer area; meanwhile, the optical disc drive makes an estimation to see if the retrieved defect management data are hot or not. Those qualified as hot defect management data in the second buffer area are then copied to the third buffer area as new cached defect management data. The optical disc drive also replaces the defect data in the first buffer area by the retrieved defect management data, and outputs replaced data to complete the data reading operation.
For an illustration of this process, please refer to
Next, as shown in the sub-diagram (c) in
Please refer to
If the defect management data of the required data block are not found in the third buffer area, the flow then proceeds with step S4 to search the defect management area on the optical disc for defect management data of the required data block, and then store the retrieved defect management data into the second buffer area. Next, in step S5, the optical disc drive checks if the defect management data in the second buffer area are qualified as hot defect management data. If the defect management data are not qualified as hot defect management data, the flow then proceeds with step S7 to directly replace defect data in the first buffer area with the defect management data to derive corrected data of the required data block. Next, in step S8, the optical disc drive outputs the corrected data in the first buffer area to the host to complete the data reading of the data block. If the defect management data is qualified as hot defect management data, the flow then proceeds with step S6 to copy the defect management data stored in the second buffer area to the third buffer area as cache data. Next, in step S7, the optical disc drive directly replaces defect data in the first buffer area with the defect management data to derive corrected data of the required data block. Then, in step S8, the optical disc drive outputs the corrected data in the first buffer area to the host to complete the data reading of the data block.
Based on the aforementioned steps of accessing the defect management data, the method of accessing defect management data according to the present invention is capable of estimating characteristics of defect management data and shifting hot defect management data in the course of accessing defect management data when an optical disc drive reads an optical disc. Furthermore, the method of accessing defect management data according to the present invention also allocates a third buffer area in the memory to cache hot defect management data, and thus builds a data cache area for defect management data. The data cache area is checked as first priority when searching for defect management data. In this way, the number of times of moving the pick-up head back and forth to read the defect management data on the optical disc can be reduced, and the reading time is also shortened. The objective of enhancing the reading efficiency is thereby accomplished.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.
Number | Date | Country | Kind |
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096150418 | Dec 2007 | TW | national |