Optical Disc Encoding with Subversive DSV Copy Protection
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Solution Overview
Problem
Existing methods for copy protecting optical discs, such as CDs and DVDs, are ineffective against unauthorized copying due to difficulties in writing and reproducing data patterns with poor Digital Sum Value (DSV) characteristics.
Innovation Solution
A method of encoding user data using a multimodal code that incorporates selected data symbols to force the encoder to output subversive sequences of code words with large absolute DSV values, which provide unbalanced dc content and act as an authenticating signature, making it difficult to copy the disc.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data patterns with poor DSV characteristics are added to provide copy protection, then copy protection effectiveness is improved, but manufacturing precision deteriorates due to difficulty in writing the authenticating signature
Solution Approach 1:
The patent changes the DSV parameter characteristics of the data patterns by selecting specific code words with large absolute DSV values. This parameter modification creates unbalanced DC content that causes writing difficulties for CD writers, thereby improving copy protection effectiveness while maintaining controlled manufacturing precision through deliberate parameter selection
Solution Approach 2:
The patent converts the harmful effect of poor DSV characteristics (which cause writing difficulties) into a beneficial copy protection mechanism. By deliberately introducing data patterns with large absolute DSV values, the writing errors that would normally be considered defects are transformed into authentication signatures that prevent unauthorized copying
2Manufacturing precision
If areas of unbalanced dc content are restricted in size, then manufacturing precision is improved, but copy protection effectiveness deteriorates
Solution Approach 1:
The patent applies local quality by restricting the size and distribution of unbalanced DC content areas to specific locations on the disc. By controlling the spatial distribution and limiting the extent of these areas, the patent maintains manufacturing precision and playback compatibility in most regions while concentrating copy protection features in controlled local zones
3Reliability
If subversive sequences with large absolute DSV values are encoded, then copy protection effectiveness is improved, but device complexity increases due to multimodal code requirements
Solution Approach 1:
The patent applies preliminary action by pre-selecting and incorporating specific data symbols into the user data before encoding. These predetermined symbols are chosen to force the encoder to output subversive sequences with large absolute DSV values, thereby simplifying the overall process by preparing the input data in advance rather than requiring complex real-time encoder modifications
Data Source
AI summary
Subversive DSV (SDSV) sequences of data symbols having a large absolute value of DSV are extremely valuable in the copy protection of optical discs as they can induce uncorrectable read errors. However, very few SDSV sequences of data symbols can be found in multimodal codes such as Eight-to-Sixteen Modulation (ESM) utilised in DVDs. It is required to select data symbols, for encoding using a multimodal code, which are capable of forcing an encoder to produce at least one subversive sequence of code words. A possible code word for a data symbol is selected if the code word has a large absolute value of DSV and there are no alternative code words, or all alternative code words are equivalent, or all alternatives except one are ruled out by RLL rules.