Video Watermarking via QDCT Coefficient Processing
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Solution Overview
Problem
Traditional video watermarking techniques introduce perceptible artifacts, have high bitrate requirements, are not transparent, and require complex detection processes, straining hardware resources and compromising video quality.
Innovation Solution
A method of embedding watermarks in video signals by processing Quantized Discrete Cosine Transform (QDCT) coefficients before entropy coding, allowing for reversible watermarking with minimal bitrate impact and efficient detection, using functions like coefficient shifting and expansion to embed and extract watermarks without decompressing the video signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional video watermarking techniques are used, then watermark embedding is achieved, but perceptible artifacts are introduced and video quality deteriorates
Solution Approach 1:
The patent segments the video signal into frequency components through QDCT transformation, separating the watermark embedding process from the visible video content. By operating on transformed coefficients rather than pixel values, the watermark is embedded in the frequency domain where it does not create perceptible artifacts in the spatial domain.
Solution Approach 2:
The patent transitions from spatial domain watermarking to frequency domain watermarking by applying QDCT. This dimensional change allows watermark embedding to occur in a different representation space where the human visual system is less sensitive, thereby avoiding perceptible artifacts while maintaining watermark reliability.
2Loss of information
If traditional video watermarking techniques are used, then watermark data is embedded, but bitrate requirements increase significantly
Solution Approach 1:
The patent changes the parameter space by operating on QDCT coefficients with varying magnitudes. By embedding watermark information in the magnitude and sign of these coefficients, the method achieves high watermark capacity without proportionally increasing bitrate, as the watermark is encoded through subtle parameter modifications rather than adding separate data streams.
Solution Approach 2:
The QDCT coefficients serve multiple functions: they represent the video content for compression and simultaneously carry the watermark information. This multi-functionality allows the same data structure to fulfill both video transmission and watermark embedding purposes, avoiding the need for separate bitrate allocation for watermark data.
3Measurement precision
If traditional video watermarking techniques are used, then watermark embedding is performed, but detection processes become complex and hardware resources are strained
Solution Approach 1:
The patent performs preliminary QDCT transformation during the video encoding process, before watermark detection is needed. The watermark is embedded in the transformed coefficients at this stage, and the same transformed representation is used for both compressed video storage and subsequent watermark extraction, eliminating the need for complex reverse transformation and re-processing during detection.
Solution Approach 2:
The compressed video bitstream itself contains all the necessary information for watermark detection. The detection process uses the already-decoded QDCT coefficients from the compression process, making the watermark detection system self-sufficient without requiring additional computational resources or complex external processing systems.
4Reliability
If watermarking is applied to video signals, then authentication capability is provided, but video transparency is compromised
Solution Approach 1:
The patent applies watermark embedding selectively to specific QDCT coefficients based on their magnitude and position. By concentrating watermark embedding in coefficients that are less critical for visual quality or have sufficient magnitude to accommodate watermark modifications, the method maintains video transparency in visually important regions while providing authentication capability through watermarking in less sensitive regions.
Data Source
AI summary
A method of embedding a bit or more of watermark data in a video signal to be entropy coded, wherein the video signal may be a block with levels, wherein the method may include: obtaining the watermark data; and obtaining a value of a first watermarked level on the basis of a first level of the block by processing the value of the first watermarked level. There also is a method of detecting a watermark in a video signal, the video signal having been entropy decoded and with a block with a first watermarked level, wherein the method may include: receiving the video signal; obtaining at least one bit of watermark data wi′ on the basis of the first watermarked level; and determining a tampering indicator by verifying whether the obtained watermark data wi′ corresponds with watermark data wi.