CAVLC Bitstream Watermarking via Syntax Element Modification
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Solution Overview
Problem
Existing mechanisms for modifying coded data in advanced coding schemes are inadequate for providing effective watermarking capabilities, as they often introduce perceptible artifacts and require time-consuming decompression and recompression processes.
Innovation Solution
A method for directly modifying entropy-encoded bitstreams, such as those using Context-based Adaptive Variable Length Coding (CAVLC), by changing macroblock types and syntax elements without entropy decoding and re-encoding, allowing for the embedding of watermarks that are imperceptible and robust to bitstream modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing mechanisms for modifying coded data are used, then watermarking can be achieved, but the process introduces perceptible artifacts and requires time-consuming decompression and recompression
Solution Approach 1:
The patent replaces the traditional mechanical decompression-modification-recompression process with a direct bitstream manipulation approach. By operating on the encoded syntax elements and bit patterns in the compressed domain, the system avoids the perceptible artifacts introduced by pixel-domain processing while eliminating the need for full decompression and recompression cycles.
Solution Approach 2:
The patent modifies specific parameters within the compressed bitstream, such as syntax element values, motion vector components, and macroblock type indicators. These parameter changes are made directly in the compressed domain, allowing watermark embedding without decompression, thereby avoiding artifact generation while maintaining coding efficiency.
2Reliability
If existing mechanisms for modifying coded data are used, then watermarking can be achieved, but the process requires time-consuming decompression and recompression
Solution Approach 1:
The patent substitutes the time-consuming mechanical decompression-modification-recompression workflow with a direct compressed-domain manipulation system. By operating on syntax elements and bit patterns without full decompression, the processing time is dramatically reduced while maintaining watermarking effectiveness.
Solution Approach 2:
The patent performs watermark embedding as a preliminary action directly on the compressed bitstream before any decompression occurs. This approach allows the watermark to be embedded efficiently in the compressed domain, eliminating the need for subsequent recompression operations and significantly reducing overall processing time.
3Adaptability or versatility
If traditional watermarking methods are applied to coded data, then watermark embedding is possible, but the methods are inadequate for advancing coding schemes
Solution Approach 1:
The patent creates a universal watermarking framework that operates on the common structural elements of various advanced coding schemes (H.264, H.265, etc.). By targeting generic syntax elements like motion vectors, macroblock types, and prediction modes that exist across multiple coding standards, the system achieves broad adaptability without requiring scheme-specific modifications.
Solution Approach 2:
The patent modifies coding parameters and syntax elements that are fundamental to multiple advanced coding schemes. By changing values of universal parameters such as motion vector precision, macroblock partitioning, and prediction mode indicators, the system achieves compatibility with evolving coding standards while maintaining effective watermarking capability.
Data Source
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AI summary
Various implementations are provided for, for example, determining watermarking data, performing the watermarking, and processing watermarked data. At least one implementation watermarks AVC bitstream that uses CAVLC entropy coding. The watermarking data may be determined in a pre-processing stage and stored for later use in watermark a bitstream. One method accesses (810) variable-length encoded data including an encoding of information identifying an actual reference used to predictively encode an image. The encoding of the information has a particular value. The method determines (830) an alternative value that is different from the particular value, such that the alternative value is an encoding of alternative information that identifies a different reference from the actual reference. The alternative value is for use in watermarking the variable-length encoded data.