Method for decoding disc information

Abstract

A pre-treating circuit for accessing the disc and a method thereof, which are especially used for treating the signal waveform that violates the encoding rule of the disc information, are provided. The present invention can modulate the signal waveform that violates the encoding rule, so that the waveform is not changed during at least 3 continuous periods of the clock signal. The present invention also replaces any wrong 16-bit data which violate the encoding rule, with approximated 16-bit data before they are decoded, or receives approximated 8-bit data which correspond to the incorrect 16-bit data, by directly referring to a table. Therefore, the subsequent decoding module can acquire more data for continuous processing, so as to improve the data reading reliability and to prevent the “picky disc” or “disc error reading” problem from happening.

1. A method for decoding disc information, comprising the steps of:
 receiving an original data signal and a clock signal; 
 modulating the original data signal when a duration of the same status of the original data signal is less than a minimum transit period of the clock signal, so as to obtain a guaranteed-waveform data signal, wherein the duration of the same status of the guaranteed-waveform data signal is greater than the minimum transit period of the clock signal, comprising: 
 generating a first reference data signal according to the original data signal, wherein the first reference data signal lags behind the original data signal, and the two signals differ by at least one reference lag period of the clock signal; further, a rising edge of the first reference data signal is generated fixed on transit edge of the clock signal, and the duration of the same status of the first reference data signal is greater than or equal to the minimum transit period of the clock signal; 
 delaying the first reference data signal so as to obtain a second reference data signal, wherein the two signals differ by one period of the clock signal; and 
 if the duration of the same status of the original data signal is less than the minimum transit period of the clock signal and is caused by the original data signal being lagged behind the transit, the first reference data signal is used to generate the guaranteed-waveform data signal; otherwise, the second reference data signal is used to generate the guaranteed-waveform data signal; and 
 continuously decoding by using the guaranteed-waveform data signal and the clock signal, so as to obtain the disc information. 
 
     
     
       2. The method for decoding the disc information of  claim 1 , wherein the method for determining whether the original data signal lags behind the transit or not, comprises the steps of:
 counting a number of the rising edge of the clock signal that appears in the duration of the same status of the original data signal according to a rising edge of the clock signal, so as to obtain a rising edge counting value; 
 counting a number of the falling edge of the clock signal that appears in the duration of the same status of the original data signal according to a falling edge of the clock signal, so as to obtain a falling edge counting value; and 
 when the rising edge counting value is greater than the falling edge counting value, it is determined that the original data signal lags behind the transit. 
 
     
     
       3. The method for decoding the disc information of  claim 1 , wherein the reference lag period is 1.5 period of the clock signal. 
     
     
       4. The method for decoding the disc information of  claim 1 , wherein the transit edge is either a rising edge or a falling edge of the clock signal. 
     
     
       5. The method for decoding the disc information of  claim 1 , wherein the minimum transit period is 3 periods of the clock signal. 
     
     
       6. A method for decoding disc information, comprising:
 receiving an original data signal and a clock signal;   modulating the original data signal if a duration of a same status of the original data signal is less than a minimum transit period of the clock signal to obtain a guaranteed-waveform data signal, wherein the duration of the same status of the guaranteed-waveform data signal is greater than or equal to the minimum transit period of the clock signal, comprising:
 generating a first reference data signal according to the original data signal, wherein the first reference data signal lags behind the original data signal, and the two signals differ by at least one reference lag period of the clock signal; 
 further, a rising edge of the first reference data signal is generated fixed on transit edge of the clock signal, and the duration of the same status of the first reference data signal is greater than or equal to the minimum transit period of the clock signal; 
 delaying the first reference data signal to obtain a second reference data signal, wherein the two signals differ by one period of the clock signal; and 
 if the duration of the same status of the original data signal is less than the minimum transit period of the clock signal and is caused by the original data signal being lagged behind the transit, the first reference data signal is used to generate the guaranteed-waveform data signal; 
   otherwise, the second reference data signal is used to generate the guaranteed-waveform data signal; and   continuously decoding by using the guaranteed-waveform data signal and the clock signal to obtain the disc information.   
     
     
       7. The method for decoding the disc information of claim 6, wherein the method for determining whether the original data signal lags behind the transit or not, comprises:
 counting a number of the rising edge of the clock signal that appears in the duration of the same status of the original data signal according to a rising edge of the clock signal to obtain a rising edge counting value;   counting a number of the falling edge of the clock signal that appears in the duration of the same status of the original data signal according to a falling edge of the clock signal to obtain a falling edge counting value; and   if the rising edge counting value is greater than the falling edge counting value, determining that the original data signal lags behind the transit.   
     
     
       8. The method for decoding the disc information of claim 7, wherein the reference lag period is 1.5 period of the clock signal. 
     
     
       9. The method for decoding the disc information of claim 6, wherein the transit edge is either a rising edge or a falling edge of the clock signal. 
     
     
       10. The method for decoding the disc information of claim 6, wherein the minimum transit period is 3 periods of the clock signal. 
     
     
       11. An apparatus, comprising:
 means for receiving an original data signal and a clock signal;   means for modulating the original data signal if a duration of a same status of the original data signal is less than a minimum transit period of the clock signal to obtain a guaranteed-waveform data signal, wherein the duration of the same status of the guaranteed-waveform data signal is greater than or equal to the minimum transit period of the clock signal, the modulating comprising:
 generating a first reference data signal according to the original data signal, wherein the first reference data signal lags behind the original data signal, and the two signals differ by at least one reference lag period of the clock signal; 
 generating a rising edge of the first reference data signal fixed on a transit edge of the clock signal, wherein the duration of the same status of the first reference data signal is greater than or equal to the minimum transit period of the clock signal; 
 delaying the first reference data signal to obtain a second reference data signal, wherein the two signals differ by one period of the clock signal; and 
 if the duration of the same status of the original data signal is less than the minimum transit period of the clock signal and is caused by the original data signal being lagged behind the transit, the first reference data signal is used to generate the guaranteed-waveform data signal; 
   otherwise, the second reference data signal is used to generate the guaranteed-waveform data signal; and   means for continuously decoding by using the guaranteed-waveform data signal and the clock signal to obtain the disc information.   
     
     
       12. An apparatus, comprising:
 a component configured to receive an original data signal and a clock signal;   a component configured to modulate the original data signal if a duration of a same status of the original data signal is less than a minimum transit period of the clock signal to obtain a guaranteed-waveform data signal, wherein the duration of the same status of the guaranteed-waveform data signal is greater than or equal to the minimum transit period of the clock signal, the modulating comprising:
 generating a first reference data signal according to the original data signal, wherein the first reference data signal lags behind the original data signal, and the two signals differ by at least one reference lag period of the clock signal; 
 generating a rising edge of the first reference data signal fixed on a transit edge of the clock signal, wherein the duration of the same status of the first reference data signal is greater than or equal to the minimum transit period of the clock signal; 
 delaying the first reference data signal to obtain a second reference data signal, wherein the two signals differ by one period of the clock signal; and 
 if the duration of the same status of the original data signal is less than the minimum transit period of the clock signal and is caused by the original data signal being lagged behind the transit, the first reference data signal is used to generate the guaranteed-waveform data signal; 
   otherwise, the second reference data signal is used to generate the guaranteed-waveform data signal; and   a component configured to continuously decode by using the guaranteed-waveform data signal and the clock signal to obtain the disc information.