Phase discontinuity compensation in a bit-accurate optical drive

1. A method of reading a block of data stored on an optical disc, the data block including header information, the method comprising the steps of:

synthesizing header information for the data block;

recovering actual header information from the disc; and

recovering actual user data from the disc, the user data being phase-shifted by a phase difference between the synthesized and recovered header information.

2. The method of claim 1 , wherein the step of synthesizing the header information includes the steps of recovering address information from a wobble embossed on the disc; and synthesizing the header information from the recovered address information.

3. The method of claim 1 , wherein the step of synthesizing the header information includes the steps of obtaining address information from the disc; and synthesizing the header information from the obtained address information.

4. The method of claim 3 , wherein multiple candidates are synthesized from the address; wherein a phase difference between the actual header information and a best candidate is determined; and wherein the recovered user data is shifted according to the determined phase difference.

5. The method of claim 3 , wherein the header information is synthesized by modulation encoding the address information according to a pre-specified format.

6. The method of claim 1 , wherein the synthesized header information includes a sector address.

7. The method of claim 1 , wherein the synthesized header information includes a sector address and an error detection code.

8. The method of claim 1 , wherein a combination of analog and digital techniques are used to phase-shift the recovered user data.

9. The method of claim 1 , wherein a read clock is used to recover the user data; and wherein the recovered user data is phase shifted by creating a phase difference between the read clock and the recovered user data.

10. The method of claim 9 , wherein the recovered user data is phase shifted by time-delaying the recovered user data.

11. The method of claim 9 , wherein the recovered user data is phase-shifted by time-delaying the read clock.

12. The method of claim 1 , wherein the recovered user data is stored in memory prior to demodulation; and wherein the recovered user data is digitally phase-shifted by shifting the data stored in the memory.

13. The method of claim 1 , wherein a phase difference is determined for only the first data sector of the block.

14. The method of claim 1 , wherein a read clock is used to recover the block from the disc; and wherein the phase difference is faded to zero according to a time constant related to the read clock.

15. A bit-accurate read/write drive for reading a data block from a disc, the drive comprising:

means for synthesizing header information for the data block;

means for recovering actual header information from the disc; and

means for recovering actual user data from the disc, the user data being phase-shifted by a phase difference between the synthesized and actual header information.

16. Apparatus for reading a block of data from an optical disc, the apparatus comprising:

an optical pickup unit;

an address detector;

a data recovery circuit for recovering data from an output of the optical pickup unit, the recovered data including actual header information and actual user data of the data block;

a first circuit for synthesizing header information for the data block;

a second circuit for determining a phase difference between the recovered actual header and synthesized header information; and

a third circuit for phase-shifting the recovered user data by the determined phase difference.

17. The apparatus of claim 16 , wherein the first circuit synthesizes the header information by recovering address information from a wobble embossed on the disc; and synthesizing the header information from the recovered address information.

18. The apparatus of claim 16 , wherein address information is contained on the disc; and wherein the first circuit synthesizes the header information from the address information contained on the disc.

19. The apparatus of claim 18 , wherein the second circuit generates multiple candidates from the address information and determines the phase difference as the phase difference between the recovered actual header information and a best candidate.

20. The apparatus of claim 16 , wherein the third circuit includes a variable delay for phase-shifting by a fractional portion of the phase difference and memory for shifting by an integer portion of the phase difference.

21. The apparatus of claim 16 , wherein the data recovery circuit includes a read clock; and wherein the recovered actual data is phase-shifted by creating a phase difference between the read clock and the recovered actual user data.

22. The apparatus of claim 21 , wherein the recovered data is phase shifted by time-delaying the recovered actual user data.

23. The apparatus of claim 21 , wherein the recovered data is phase-shifted by time-delaying the read clock.

24. The apparatus of claim 16 , wherein the data recovery circuit includes a read clock; and wherein the second circuit determines a phase difference only for the first data sector of the block and fades the phase difference to zero according to a time constant related to the read clock.

25. The apparatus of claim 16 , wherein the apparatus is a DVD drive.

26. Apparatus for correcting a signal recovered during a read operation on a data block stored on a disc, the recovered signal including actual header information and actual user data of the data block, the apparatus comprising:

a first circuit for synthesizing header information for the data block;

a second circuit for determining a phase difference between the recovered and synthesized header information; and

a third circuit for phase-shifting the recovered user data by the determined phase difference.