Enabling accurate demodulation of a DVD bit stream using devices including a SYNC window generator controlled by a read channel bit counter

• US 6,536,011 B1
• Filed: 10/22/1998
• Issued: 03/18/2003
• Est. Priority Date: 10/22/1998
• Status: Expired due to Term

• Current Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Original Assignee: Oak Technology Partners (Qualcomm, Inc.)
• Inventors: Jang, Eric, Bhattacharya, Arup K., Chou, Chen-Chi
• Primary Examiner(s): Psitos, Aristotelis M
• Assistant Examiner(s): LAMARRE, GUY J
• Application Number:
  US09/176,853
• Time in Patent Office: 1,608 Days
• Field of Search: 386/46, 386/84, 386/126, 386/2, 369/47-49, 369/53.34, 369/47.28, 360/51, 360/50, 360/26, 714/814, 714/798, 714/811, 714/819, 714/775
• US Class Current: 714/814
• CPC Class Codes: G11B 2220/2562 DVDs [digital versatile discs]; Digital video discs; MMCDs; HDCDs
• CPC Class Codes: G11B 27/3027 used signal is digitally coded

Abstract

A method of processing a DVD bitstream includes the steps of reading the DVD bitstream, the bitstream including a sync frame. A sync window is created, the sync window being open at least during the expected timing of a sync detection signal within the sync frame. The sync pattern is detected within the sync frame and the sync detection signal is generated only when the sync pattern has been detected and the sync window is open. A DVD sync pattern detection circuit includes a sync window generator to generate a sync window signal, a sync pattern detector, the sync pattern detector generating a sync detection signal only when both a sync pattern is detected in a DVD input stream and the sync window signal is asserted. A read channel bit counter generates a read counter signal to control the sync window generator, the read channel bit counter being reset when the sync pattern detector detects the sync pattern. The read channel bit counter controls the width of the sync window signals to allow the generation of correctly timed demodulation enable signals even when the sync frames have non-standard bit lengths. The sync windows also prevent the erroneous detection of sync patterns within the data portions of the sync frames. A pseudo sync detection signal is generated when the sync pattern is corrupted or missing from the sync frame.

Claims

1. A method of processing a DVD bitstream, comprising the steps of:

reading the DVD bitstream, the bitstream including a sync frame;

creating a sync window, the sync window being open at least during an expected timing of a sync detection signal within the sync frame;

detecting the sync pattern within the sync frame;

generating the sync detection signal only when the sync pattern has been detected and the sync window is open;

detecting a sync frame boundary;

outputting a demodulation enable signal every 16 bits after generation of the sync detection signal until the sync frame boundary is detected, and

counting read channel bits of the DVD bitstream in a counter, and resetting the counter upon generation of the sync detection signal and upon reaching the sync frame boundary.

2. The method of claim 1, wherein, in single-bit mode, the sync window is open 2 bits before the expected timing of the sync detection signal and 2 bits after the generation of the sync detection signal.

3. The method of claim 1, wherein, in dual bit mode, the sync window is open 1 bit before the expected timing of the sync detection signal and 1 bit after the generation of the sync detection signal.

4. The method of claim 1, wherein, in quad-bit mode, the sync window is open only during the expected timing of the sync detection signal.

5. The method of claim 1, wherein the resetting step resets the counter to a value that accounts for a timing difference between the expected timing of the sync detection signal and a timing of the generation of the sync detection signal.

6. The method of claim 1, further comprising the step of generating a pseudo sync detection signal after the sync window closes when no sync detection signal is generated during a time when the sync window is open.

7. A DVD sync pattern detection circuit, comprising:

a sync window generator to generate a sync window signal;

a sync pattern detector, the sync pattern detector generating a sync detection signal only when both a sync pattern is detected in a DVD input stream and the sync window signal is asserted; and

a read channel bit counter, the read channel bit counter generating a read counter signal to control the sync window generator and being reset when the sync pattern detector detects the sync pattern, the read channel bit counter generating a demodulation enable signal during a data portion of a sync frame when a four least significant bits of the read channel bit counter are zero.

8. The DVD sync pattern detection circuit of claim 7, wherein the sync window generator further comprises means for generating a pseudo-sync signal, the pseudo-sync signal being generated when the sync pattern detector fails to detect a sync pattern when the sync window signal is asserted.

9. The DVD sync pattern detection circuit of claim 8, further comprising a logic circuit coupled to the sync pattern detector and to the sync window generator, the logic circuit outputting a sync signal upon assertion of one of the pseudo-sync signal and the sync detection signal.

10. The DVD sync pattern detection circuit of claim 9 wherein the logic circuit includes an OR logic circuit.

11. The DVD sync pattern detection circuit of claim 7, wherein the read channel bit counter includes an 11-bit counter.

12. The DVD sync pattern detection circuit of claim 7, wherein the read counter signal controls a width of the sync window signal and wherein, in single-bit mode, the sync window signal is asserted 2 bits before an expected timing of the sync detection signal and de-asserted 2 bits after the generation of the sync detection signal.

13. The DVD sync pattern detection circuit of claim 7, wherein the read counter signal controls a width of the sync window signal and wherein, in dual-bit mode, the sync window signal is asserted 1 bit before an expected timing of the sync detection signal and de-asserted 1 bit after the generation of the sync detection signal.

14. The DVD sync pattern detection circuit of claim 7, wherein, in quad-bit mode, the sync window signal is asserted only during an expected timing the sync detection signal.

15. A DVD controller, comprising:

means for reading a DVD bitstream;

means for generating a sync window signal;

means for detecting a sync pattern within the DVD bitstream, the sync pattern detecting means generating a sync detection signal only when both the sync pattern is detected and the sync window signal is asserted; and

means for counting channel bits, the channel bit counting means generating a read counter signal to control the sync window signal generating means and resetting when the sync pattern detecting means detects the sync pattern, the channel bit counting means including means for generating a demodulation enable signal during a data portion of a sync frame when a four least significant bits of the read channel bit counting means are zero.

16. The DVD controller of claim 15, wherein the sync window signal generating means further comprises means for generating a pseudo-sync signal, the pseudo-sync signal being generated when the sync pattern detecting means fails to detect a sync pattern when the sync window signal is asserted.

17. The DVD controller of claim 16, further comprising a logic circuit coupled to the sync pattern detecting means and to the sync window signal generating means, the logic circuit outputting a sync signal upon assertion of one of the pseudo-sync signal and the sync detection signal.

18. The DVD controller of claim 15, wherein the read counter signal controls a width of the sync window signal and wherein, in single-bit mode, the sync window signal generating means asserts the sync window signal 2 bits before an expected timing of the sync detection signal and de-asserts the sync window signal 2 bits after the generation of the sync detection signal.

19. The DVD controller of claim 15, wherein the read counter signal controls a width of the sync window signal and wherein, in dual-bit mode, the sync window signal generating means asserts the sync window signal 1 bit before an expected timing of the sync detection signal and de-asserts the sync window signal 1 bit after the generation of the sync detection signal.

20. The DVD controller of claim 15, wherein, in quad-bit mode, the sync window signal generating means asserts the sync window only during an expected timing the sync detection signal.

21. A DVD bitstream processing circuit, comprising:

a sync window signal generator;

a sync pattern detector to detect a sync pattern within a DVD bitstream, the sync pattern detector generating a sync detection signal only when both the sync pattern is detected and a sync window signal is asserted; and

a channel bit counter, the channel bit counter generating a read counter signal to control the sync window signal generator and resetting when the sync pattern detector detects the sync pattern, the channel bit counter generating a demodulation enable signal during a data portion of a sync frame when a four least significant bits of the read channel bit counter are zero.

22. The DVD bitstream processing circuit of claim 21, wherein the sync window signal generator further generates a pseudo-sync signal, the pseudo-sync signal being generated when the sync pattern detector fails to detect a sync pattern when the sync window signal is asserted.

23. The DVD bitstream processing circuit of claim 22, further comprising a logic circuit coupled to the sync pattern detector and to the sync window signal generator, the logic circuit outputting a sync signal upon assertion of one of the pseudo-sync signal and the sync detection signal.

24. The DVD bitstream processing circuit of claim 21, wherein the read counter signal controls a width of the sync window signal and wherein, in single-bit mode, the sync window signal generator asserts the sync window signal 2 bits before an expected timing of the sync detection signal and de-asserts the sync window signal 2 bits after the generation of the sync detection signal.

25. The DVD bitstream processing circuit of claim 21, wherein the read counter signal controls a width of the sync window signal and wherein, in dual-bit mode, the sync window signal generator asserts the sync window signal 1 bit before an expected timing of the sync detection signal and de-asserts the sync window signal 1 bit after the generation of the sync detection signal.

26. The DVD bitstream processing circuit of claim 21, wherein, in quad-bit mode, the sync window signal generator asserts the sync window only during an expected timing the sync detection signal.