Optical Disc BCA Sync Detection Using Internal Clock
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Solution Overview
Problem
Existing methods for reading data from the burst cutting area (BCA) of optical discs require detection of the sync byte with a phase locked loop (PLL), which fails if synchronization is lost, preventing decoding if the sync byte is not detected or if there is deviation from synchronization.
Innovation Solution
A method and apparatus that use an internal clock to detect a sync pattern by counting consecutive falling edges of the BCA signal, allowing demodulation to begin with detection of a resync byte having sync ID 1, and includes error correction for undetected information rows, eliminating the need for PLL synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a phase locked loop (PLL) is used to detect the sync byte and extract a clock synchronized with the BCA bit cycle, then the sync byte detection can be performed with proper synchronization, but the system fails when synchronization is lost or deviated, preventing decoding
Solution Approach 1:
The patent extracts the clock signal generation from the external PLL synchronization system and uses the internal clock of the BCA data processor instead. This eliminates the dependency on external synchronization while maintaining the ability to detect sync patterns and perform decoding, thereby improving reliability without requiring complex synchronization mechanisms.
Solution Approach 2:
The BCA data processor uses its own internal clock to detect sync patterns and perform demodulation, making the system self-sufficient. The internal clock serves both as the operating clock for the processor and as the reference for detecting the sync pattern, eliminating the need for external PLL synchronization and improving system autonomy and reliability.
2Measurement precision
If the sync byte with ID 0 is required to start data acquisition and decoding, then proper synchronization can be established, but decoding cannot take place if the sync byte is not detected or if there is deviation from synchronization
Solution Approach 1:
The patent performs preliminary detection of any sync pattern (not just the specific sync byte with ID 0) to establish the starting point for demodulation. By detecting any valid sync pattern first and then identifying the associated sync ID, the system ensures that data acquisition can begin even if the specific sync byte with ID 0 is not detected, thereby improving decoding reliability while maintaining detection accuracy.
3Speed
If PLL synchronization with the BCA bit cycle is required, then accurate clock extraction is achieved, but any deviation from synchronization causes decoding failure
Solution Approach 1:
The patent dynamically adapts the demodulation process to work with the internal clock of the BCA data processor rather than requiring strict external synchronization. The system can tolerate variations in clock timing and still successfully detect sync patterns and perform demodulation, making the system more adaptable to different operating conditions while maintaining adequate clock accuracy for reliable data recovery.
Data Source
AI summary
A method and an apparatus for detecting BCA on the surface of an optical disc are disclosed. The method includes utilizing an internal free running clock to detect a sync pattern, starting demodulation of data on detection of sync ID 1 by utilizing the internal free running clock, and utilizing the transition between row boundaries to determine which sync ID 1 was used for initializing demodulation.