Patent Application
20100226227
The disclosed embodiments relate to methods and apparatuses of processing readback signal generated from reading optical storage medium.
Optical storage media, such as read-only, recordable, or rewritable optical discs, have become popular data carriers nowadays. In general, the stored data are reproduced from reading a recording layer (i.e., a reflective layer) of an optical storage medium through directing a laser beam onto the recording layer and then detecting signals reflected from the recording layer. To protect the recording layer (reflective layer), a protective layer made of, for example, polycarbonate is generally formed on the recording layer. Therefore, the laser beam emitted from a laser diode has to pass through the protective layer before arriving at the recording layer (i.e., the reflective layer); similarly, the laser beam reflected from the recording layer (i.e., the reflective layer) has to pass through the protective layer before being detected by a photo sensor. Therefore, the signal quality of the reflected laser beam detected by the photo sensor is actually affected by the protective layer.
However, an optical disc might have a defective area due to scratch, dirt, or fingerprint on a surface of the protective layer. Please refer to
Please refer to
Please refer to
As mentioned above, the RF signal affected by the fingerprint/dirt does not disappear completely. Therefore, how to process the RF signal affected by the fingerprint/dirt for allowing the following decoding process to correctly derive information from the RF signal affected by the fingerprint/dirt becomes an important issue for designers. In other words, there is a need of a method and apparatus to improve performance of reading defective areas on the optical storage medium, especially the defective areas caused by fingerprint/dirt.
In accordance with exemplary embodiments of the present invention, the present invention provides methods and apparatuses of processing a readback signal (e.g., an RF signal) generated from reading an optical storage medium (e.g., an optical disc) for improving performance of reading defective areas on the optical storage medium.
According to a first aspect of the present invention, an exemplary method of processing a readback signal generated from reading an optical storage medium is provided. The method includes: performing a defect detection according to the readback signal to generate a defect detection result indicating defective areas on the optical storage medium; and performing a parameter calibration upon at least a parameter associated with processing of the readback signal according to the defect detection result.
According to a second aspect of the present invention, an exemplary apparatus for processing a readback signal generated from reading an optical storage medium is provided. The apparatus includes a defect detection block and a parameter calibration block. The defect detection block is implemented for performing a defect detection according to the readback signal to generate a defect detection result indicating defective areas on the optical storage medium. The parameter calibration block is coupled to the defect detection block, and implemented for performing a parameter calibration upon at least a parameter associated with processing of the readback signal according to the defect detection result.
According to a third aspect of the present invention, a method of processing a readback signal generated from reading an optical storage medium is provided. The method includes: deriving identification information of the optical storage medium according to the readback signal; performing a parameter calibration upon at least one parameter associated with processing of the readback signal, thereby deriving a calibrated parameter setting; and recording the calibrated parameter setting indexed by the identification information in a storage device.
According to a fourth aspect of the present invention, an apparatus for processing a readback signal generated from reading an optical storage medium is provided. The apparatus includes an optical storage access block, a parameter calibration block, a storage device, and a control block. The optical storage access block is implemented for deriving the readback signal and deriving identification information of the optical storage medium according to the readback signal. The parameter calibration block is coupled to the optical storage access block, and is implemented for performing a parameter calibration upon at least one parameter associated with processing of the readback signal, thereby deriving a calibrated parameter setting. The control block is coupled to the calibration block, the optical storage access block and the storage device, and is implemented for recording the calibrated parameter setting indexed by the identification information in the storage device.
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.
Certain terms are used throughout the following description and claims to refer to particular system components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ” The terms “couple” and “couples” are intended to mean either an indirect or a direct electrical connection. Thus, if a first device couples to a second device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections.
In this embodiment, the signal generation block 308 includes a signal synthesizer 322 and a signal processor 324 including an extreme value tracking unit 326 and a filter unit 328. The signal synthesizer 322 is implemented for generating a readback signal S1, such as a radio frequency (RF) signal, according to signals reflected from the optical disc 301 and then detected by a photo sensor (not shown) in the optical pick-up head 304. The signal processor 324 is implemented for processing the readback signal S1 to generate a processed readback signal (e.g., a processed RF signal) S2. In the signal processor 324, the extreme value tracking unit 326 is used for tracking predetermined-type extreme values of the readback signal S1 to generate an extreme value tracking result, and the filter unit 328 is used for performing a filtering operation upon the extreme value tracking result to generate the processed readback signal S2. In one exemplary implementation, the extreme value tracking unit 326 is implemented using a peak hold circuit for tracking peak values of the readback signal S1, and the filter unit 328 is implemented using a low-pass filter for filtering out high-frequency components in the output of the peak hold circuit. Next, the processed readback signal S2 is fed into the following defect detection block 312 for further signal processing, which is detailed as follows. Please notes that the implementation of signal processor 324 is only an example, and is not meant to be limitations of the present invention. Other implementations of the signal processor 324 for processing the readback signal S1 to generate the processed readback signal for defect detection block 312 may be utilized in accordance with the design necessity.
In this exemplary embodiment, the defect detection block 312 includes a first slicer 332, a second slicer 334, and a decision logic 336. The first slicer 332 is implemented for slicing the processed readback signal S2 by a first slicer level SL1 to generate a first slicing result SRI, the second slicer 224 is implemented for slicing the processed readback signal S2 by a second slicer level SL2 to generate a second slicing result SR2, and the decision logic 336 generates the defect detection result S3 according to the first slicing result SR1 and the second slicing result SR2. Please refer to
In the exemplary embodiment shown in
In another alternative design, the defect detection block 312 is modified to include the second slicer 334 and the decision logic 336. That is, the first slicer 332 used for generating a slicing result indicating defective areas caused by scratch is omitted in this alternative design. In this way, the second slicing result SR2 directly serves as the defect detection result S3 generated from the defect detection block 312. Take the implementation of using a high-pass filter to process signal portions in the readback signal (e.g., the RF signal) S1 that correspond to defective areas caused by fingerprint/dirt as an example. The signal portion P1 in
It should be noted that above-mentioned alternative embodiments all obey the spirit of the present invention of using one or more slicers to find the defective areas caused by scratch or fingerprint/dirt, and fall with the spirit of the present invention.
Briefly summarized, the defect detection result S3 could be set by a combinational logic result such as an XOR result of the first slicing result SR1 and the second slicing result SR2, the first slicing result SR1, or the second slicing result SR2, depending upon design requirements. For example, in a case where high-pass filtering will be applied to the readback signal S1 for facilitating decoding of the signal portions corresponding to the defective areas, the combinational logic result of the first and second slicing results SR1 and SR2 or the second slicing result SR2 is preferably selected as the defect detection result S3 to indicate when to start adjusting the high-pass filtering operation. Further details are given as below.
The defect detection result S3 generated from the defect detection block 312 is delivered to the parameter calibration block 314. The parameter calibration block 314 is implemented for performing a parameter calibration upon at least one parameter associated with processing of the readback signal S1 according to the incoming defect detection result S3. When the optical pick-up head 304 is accessing a defective area caused by fingerprint/dirt, the parameter calibration block 314 is notified by the defect detection result S3 shown in
Furthermore, a high-pass filter (HPF) 342 which is one exemplary component generally implemented in the read channel block 310 can also be selectively adjusted for high-pass filtering the readback signal S1 according to the defect detection result S3. In general, the high-pass filter 342 is used to perform high-pass filtering upon an incoming signal when a normal area or a defective area is currently accessed by the optical pick-up head 304; however, in one implementation of the present invention, the filter characteristic of the high-pass filter 342 can also be adjusted when the optical pick-up head 304 is accessing a defective area. For instance, when the optical pick-up head 304 is accessing a defective area caused by, for example, fingerprint/dirt, the high-pass filter 342 is adjusted and performs high-pass filtering upon the readback signal S1 to thereby generate a filtered readback signal S1′, and then a decoder 344 decodes the filtered readback signal S1′ received from the preceding high-pass filter 342. In other words, in one implementation, the high-pass filter 342 can be selectively adjusted and the parameter calibration block 314 is enabled when a defective area identified according to the defect detection result S3 is accessed by the optical pick-up head 304. As clearly shown in
Please note that any application selectively adjusting the high-pass filtering applied to the readback signal or applying the parameter calibration to at least one parameter (e.g., the read channel parameter or servo parameter) according to the defect detection result still obeys the spirit of the present invention, and falls within the scope of the present invention.
The calibration control block 316 is implemented in the optical storage apparatus 300 for controlling operation of the parameter calibration block 314 according to a signal quality index S4 derived from the processing of the readback signal S1. For example, the signal quality index S4 could be a signal quality of a synchronization signal derived from the readback signal S1 (e.g., a SYNC_OK signal) or a decoding quality associated with decoding of the readback signal S1 (e.g., an Error Detection Code (EDC) or Identification (ID) decoding OK signal, or a decoding error count). Take the SYNC_OK signal serving as the signal quality index S4 as an example. If the readback signal S1 has signal quality that is good enough, the SYNC signal could be obtained continuously without intermission. That is, the SYNC_OK signal used for indicating the status of the SYNC signal will be kept, for example, at a high logic level. However, when the readback signal S1 fails to have signal quality satisfying the minimum requirement, the SYNC signal will have a sync loss. As a result, the SYNC_OK signal will have a low logic level to indicate such a situation. Due to the specific signal characteristic of the SYNC_OK signal, the SYNC_OK signal therefore could serve as the signal quality index S4 to indicate if the parameter calibration has calibrated the parameter using an optimized parameter setting.
In general, the readback signal (e.g., an RF signal) S1 becomes un-correctable when the decoding error count exceeds a specific value, implying that the readback signal S1 has poor signal quality and it is difficult to correctly decode such a signal. Therefore, when the optical disc 301 is a compact disc (CD), the C2 decoding error count could be used as the signal quality index; when the optical disc 301 is a digital versatile disc (DVD) or a high-definition digital versatile disc (HD-DVD), the PO (Parity of the Outer code) decoding error count could be used as the signal quality index; and when the optical disc 301 is a Blu-ray disc (BD), the Long Distance Code (LDC) decoding error count could be used as the signal quality index. As well known in the pertinent art, the PO decoding for DVD or HD-DVD and the C2 decoding for CD are more sensitive to the signal quality. For example, if the PO decoding error count or C2 decoding error count of a data block is equal to one, it is possible that the quality of the whole data block is bad. It should be noted that even though the Parity of the Inner code (PI) decoding for DVD/HD-DVD and the C1 decoding for CD is not so sensitive to the signal quality, this does not mean that the PI decoding error count/C1 decoding error count cannot be used as the signal quality index. For example, when the PI decoding error count or the C1 decoding error count of a data block is greater than an error accumulation threshold, this implies that there are too many decoding errors in the same data block, and the data block might be un-correctable due to bad signal quality of the readback signal. Therefore, the PI decoding error count or the C1 decoding error count could also be employed as the signal quality index.
Step 600: Start.
Step 602: Check a defect detection result to determine if an optical pick-up head is going to access a defective area on an optical storage medium (e.g., an optical disc). If yes, go to step 604; otherwise, go to step 602 to keep monitoring the defect detection result.
Step 604: Enable a parameter calibration.
Step 606: Calibrate at least one parameter by assigning a calibrated parameter setting to replace an original parameter setting set to the parameter, wherein the at least one parameter could include a read channel parameter, a servo parameter, or a combination thereof.
Step 608: Check if a signal quality index satisfies a predetermined criterion. If yes, go to step 612; otherwise, go to step 610.
Step 610: Calibrate the parameter by assigning another calibrated parameter setting to the parameter. Go to step 608.
Step 612: Disable the parameter calibration.
Step 614: Maintain a finally calibrated parameter setting set to the parameter.
Step 616: Check if the optical pick-up head has finished accessing the defective area. If yes, go to step 618; otherwise, go to step 616 to keep monitoring.
Step 618: Recover the parameter from the calibrated parameter setting that is assigned by the parameter calibration enabled due to accessing of the defective area to the original parameter setting. Go to step 602 to keep monitoring the defect detection result.
As shown in the flowchart in
Please refer to
Step 900: Start.
Step 902: Check a defect detection result to determine if an optical pick-up head is going to access a defective area on an optical storage medium (e.g., an optical disc). If yes, go to step 904; otherwise, go to step 902 to keep monitoring the defect detection result.
Step 904: Enable a parameter calibration.
Step 906: Calibrate at least one parameter by assigning a calibrated parameter setting to replace an original parameter setting of the parameter, wherein the at least one parameter could include a read channel parameter, a servo parameter, or a combination thereof.
Step 908: Check if a signal quality index satisfies a predetermined criterion. If yes, go to step 912; otherwise, go to step 910.
Step 910: Calibrate the parameter by assigning another calibrated parameter setting to the parameter. Go to step 908.
Step 912: Disable the parameter calibration.
Step 914: Maintain a finally calibrated parameter setting set to the parameter.
Step 916: Check if the optical pick-up head has finished accessing tracks associated with the defective area and then accessed at least a portion of a normal area. If yes, go to step 918; otherwise, go to step 916 to keep monitoring.
Step 918: Recover the parameter from the calibrated parameter setting that is assigned by the parameter calibration enabled due to accessing of the defective area to the original parameter setting. Go to step 902 to keep monitoring the defect detection result.
The exemplary parameter calibration method in
With regard to the parameter calibration method shown in
Please note that the examples shown in
As mentioned above, the parameter calibration block 314 calibrates the parameter (e.g., a read channel parameter and/or a servo parameter) to find an optimized parameter setting for the defective area accessed by the optical pick-up head 304. In an exemplary embodiment of the present invention, the defect magnitude of the defective area on the optical storage medium could be taken into consideration when the parameter calibration block 314 is enabled to calibrate at least one parameter associated with decoding of the readback signal S1. For example, the parameter calibration block 314 first identifies a defect magnitude of a defective area on the optical storage medium (e.g., the optical disc 301 ) according to the defect detection result S3. When the defect magnitude corresponds to a first level, the parameter calibration block 314 performs the parameter calibration to calibrate a first parameter associated with processing of the readback signal S1; and when the defect magnitude corresponds to a second level, the parameter calibration block 314 performs the parameter calibration to calibrate a second parameter associated with processing of the readback signal S1. In other words, the parameter to be calibrated is dynamically selected according to the defect magnitude. In an alternative implementation, the parameter calibration block 314 performs the parameter calibration to calibrate a parameter by a first parameter setting when the defect magnitude corresponds to a first level, and performs the parameter calibration to calibrate the parameter by a second parameter setting when the defect magnitude corresponds to a second level. In other words, the parameter setting assigned to the parameter to be calibrated is dynamically determined according to the defect magnitude.
When the defect magnitude is taken into consideration, the calibration time spent on finding the optimum calibrated parameter setting could be shortened due to the fact that the defect magnitude offers additional information for the parameter calibration. Please note that the aforementioned examples are for illustrative purposes only, and are not meant to be limitations of the present invention. For example, with the help of the signal quality index, the parameter calibration could employ a try-and-error methodology or other searching algorithm to find the optimum calibrated parameter setting. The same objective of finding an optimized parameter setting is achieved.
In addition to performing the parameter calibration to find the calibrated parameter setting satisfying the requirement, embodiments of the present invention also propose storing the calibrated parameter setting which includes setting values for one or more parameters associated with processing of a readback signal to improve the reading performance of an optical storage apparatus, such as an optical disc drive. For example, the setting value(s) for at least a read channel parameter (e.g., a slicer bandwidth, a Viterbi bandwidth, a PLL bandwidth, a PRML target level, a decoding strategy, an RF signal high-pass filtering bandwidth, or an RF signal amplitude), at least a servo parameter (e.g., a focus gain or a defocus setting) or a combination thereof are derived using the parameter calibration and then stored in a storage for later use. Preferably, a plurality of parameters are calibrated to make the optical storage apparatus have optimized reading performance, which also resulting in a longer period of time spent on completing the first-time parameter calibration for a loaded optical storage medium (e.g., an optical disc). However, as the calibrated parameter setting for the optical storage medium has been recorded in the optical storage apparatus, the optical storage apparatus therefore can employ the calibrated parameter setting stored therein to improve the signal quality of the readback signal to be decoded when the same optical storage medium is loaded into the optical storage apparatus again. In other words, the parameter calibration, which is enabled to calibrate a plurality of parameters associated with reading data from an optical storage medium when the signal quality of the readback signal fails to meet the requirement due to defective areas on the optical storage medium, might cause a playback interrupt perceivable to the viewer; however, after the calibrated parameter setting for these parameters is derived and stored, the following playback of the same optical storage medium loaded into the optical storage apparatus again would become smooth with the help of the stored calibrated parameter setting derived by the previous parameter calibration. Detailed operation is illustrated as follows.
The parameter calibration block 1206 is implemented for performing a parameter calibration upon at least one parameter associated with processing of the readback signal to thereby derive a calibrated parameter setting. If the aforementioned parameter calibration mechanism is employed by the optical storage apparatus 1200, the parameter calibration block 1206 can be implemented using the parameter calibration block 314 shown in
The control block 1204 is configured to activate the parameter calibration block 1206 when a specific condition is met (e.g., when the signal quality is lower than an acceptable level due to accessing a defective area on the optical disc 1201), and records the identification information of the optical disc 1201 and the calibrated parameter setting found by the parameter calibration block 1206 for the optical disc 1201 into the storage device 1208 (e.g., a memory device or other component with data storage capability). That is, the control block 1204 records the calibrated parameter setting indexed by the identification information of the optical disc 1201 in the storage device 1208 for later use. Similarly, if the aforementioned parameter calibration mechanism is employed by the optical storage apparatus 1200, the calibration control block 316 and the defect detection block 312 in
Step 1300: Start.
Step 1302: Derive identification information of an optical storage medium.
Step 1304: Refer to the identification information to check if the parameter calibration has been performed for the optical storage medium at least once. If yes, go to step 1306; otherwise, go to step 1310.
Step 1306: Load a calibrated parameter setting from a storage device according to the identification information.
Step 1308: Configure at least one parameter associated with processing of the readback signal according to the calibrated parameter setting loaded from the storage device. Go to step 1316.
Step 1310: Check if the parameter calibration should be activated. If yes, go to step 1312; otherwise, keep checking if the parameter calibration should be activated.
Step 1312: Perform the parameter calibration upon at least one parameter associated with processing of the readback signal, thereby deriving the calibrated parameter setting for the optical storage medium.
Step 1314: Record the calibrated parameter setting indexed by the identification information of the optical storage medium into the storage device.
Step 1316: End.
In most cases, the identification information of an optical storage medium is unique. Therefore, when the optical disc 1201 is loaded, the identification information derived from a table of content, a control data zone, or a file system unique signature of the optical disc 1201 is used by the control block 1204 to check if the parameter calibration block 1206 has performed the parameter calibration for the optical disc 1201 at least once (steps 1302 and 1304). Specifically, in a case where the parameter calibration block 1206 is activated by the controller block 1204 to perform the parameter calibration upon at least one parameter associated with processing of the readback signal derived from reading the optical disc 1201, a calibrated parameter setting is derived (step 1312). Next, the control block 1204 records the calibrated parameter setting indexed by the identification information into the storage device 1208 (step 1314). Therefore, by comparing the identification information of the optical disc 1201 with identification information recorded in the storage device 1208, the control block 1204 is able to know whether the parameter calibration block 1206 has performed the parameter calibration for the optical disc 1201 before. When the control block 1204 finds that the parameter calibration block 1206 has performed the parameter calibration for the optical disc 1201 at least once, meaning that the storage device 1208 should contain the calibrated parameter setting for the optical disc 1201, the control block 1204 therefore loads the calibrated parameter setting for the optical disc 1201 from the storage device 1208, and configures one or more parameters of the optical storage access block 1202 that are associated with processing the readback signal by the calibrated parameter setting loaded from the storage device 1208 regardless of which area of the optical disc 1201 is accessed now or when the calibrated parameter setting is requested due to poor signal quality of the readback signal which causes decode errors or high symbol error rate. For example, in one implementation, the calibrated parameter setting loaded from the storage device 1208 are employed by the optical storage access block 1202 when the optical storage apparatus 1200 accesses any of defective areas and normal areas of the optical disc 1201; however, in another implementation, the calibrated parameter setting loaded from the storage device 1208 are employed by the optical storage access block 1202 only when the optical storage apparatus 1200 accesses defective areas of the optical disc 1201.
When the control block 1204 finds that the parameter calibration block 1206 has not performed the parameter calibration for the optical disc 1201 yet, meaning that the storage device 1208 has no calibrated parameter setting for the optical disc 1201, the control block 1204 checks if the parameter calibration should be activated (steps 1304 and 1310). For example, when the optical storage apparatus 1200 is going to access a defective area on the optical disc 1201 or the signal quality of the readback signal is poor (i.e., the decode error occurs or the symbol error rate is higher than an acceptable level), the control block 1204 activates the parameter calibration block 1206 to perform the parameter calibration upon one or more parameters associated with processing of the readback signal to thereby derive a calibrated parameter setting, and then the control block 1204 records the calibrated parameter setting indexed by the identification information of the optical disc 1201 into the storage device 1208 (steps 1312 and 1314).
If the aforementioned parameter calibration mechanism is employed, step 1310 can be implemented using step 602 shown in
In addition, the parameter calibration block 1206 preferably calibrates one or more parameters associated with processing of the readback signal through checking the signal quality for the same data segment (e.g., the same ECC block or the same track) on the optical disc 1201 to avoid signal quality misjudgment.
Furthermore, the address of the disc area upon which the parameter calibration block 1206 performs the parameter calibration can be recorded as well. In this way, when the optical disc 1201 is loaded into the optical storage apparatus 1200 again, the control block 1204 configures one or more parameters of the optical storage access block 1202 according to a calibrated parameter setting selected according to address of a defective area accessed by the optical storage access block 1202 now. For example, the optical disc 1201 might have a plurality of defective areas formed thereon, the address data and calibrated parameter setting of each defective area are recorded into the storage device 1208. In an alternative design, the optical disc 1201 is virtually divided into a plurality of disc areas, and the address data and calibrated parameter setting for each disc area are recorded into the storage device 1208.
In the exemplary embodiment shown in
Step 1400: Start.
Step 1402: Derive identification information of an optical storage medium.
Step 1404: Refer to the identification information to check if the parameter calibration has been performed for the optical storage medium at least once. If yes, go to step 1406; otherwise, go to step 1410.
Step 1406: Load a calibrated parameter setting from a storage device according to the identification information.
Step 1408: Configure at least one parameter associated with processing of the readback signal according to the calibrated parameter setting loaded from the storage device.
Step 1410: Check if the parameter calibration should be activated. If yes, go to step 1412; otherwise, keep checking if the parameter calibration should be activated.
Step 1412: Perform the parameter calibration upon at least one parameter associated with processing of the readback signal, thereby deriving the calibrated parameter setting for the optical storage medium.
Step 1414: Record the calibrated parameter setting indexed by the identification information into the storage device.
Step 1416: End.
As a person skilled in the art can readily understand details of each step shown in
Briefly summarized, the conception of the exemplary apparatus shown in
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.
