Adaptive Down-Sampling for Digital Watermark Detection

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Solution Overview

Problem

Digital watermarks on white adhesive labels are vulnerable to shot noise interference due to their small physical scale and bright images, which complicates synchronization and decoding processes, especially when down-sampling is not adequately adjusted.

Innovation Solution

Adaptive down-sampling of captured imagery based on the scale of the watermark determined by the synchronization process reduces the standard deviation of shot noise, thereby minimizing interference and improving decoding reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If down-sampling is applied to reduce shot noise, then noise interference is reduced, but watermark detection precision deteriorates when watermarks are at small physical scales

Engineering Contradiction:

Improveshot noise interferenceVSAvoidwatermark detection precision

Core Design Contradiction:

Object-affected harmful factorsVSMeasurement precision

Solution Approach 1:

The patent implements dynamic down-sampling by adjusting the down-sampling factor based on the detected watermark scale. The system determines the scale of the watermark in the captured image and selects an appropriate down-sampling factor from a plurality of available factors, thereby optimizing the balance between noise reduction and detection precision for each specific watermark instance.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the down-sampling parameter adaptively based on watermark characteristics. By modifying the down-sampling factor according to the detected watermark scale, the system optimizes the processing parameters to reduce shot noise while maintaining adequate detection precision for watermarks at different physical scales.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If down-sampling factor is increased to reduce shot noise standard deviation, then noise interference is reduced, but watermark signal fidelity deteriorates

Engineering Contradiction:

Improvenoise reduction reliabilityVSAvoidwatermark signal fidelity

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The system dynamically adjusts the down-sampling factor based on the detected watermark scale rather than using a fixed high down-sampling factor. This dynamic adjustment ensures that the down-sampling level is optimized for each specific case, reducing noise while preserving the necessary watermark signal fidelity.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent modifies the down-sampling parameter adaptively based on watermark characteristics. By selecting from multiple down-sampling factors according to the detected watermark scale, the system optimizes the balance between noise reduction reliability and signal fidelity preservation.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11367159B1Methods and arrangements for enhancing detection of digital watermark signals

Publication Date: 2022.06.21 DIGIMARC LLC

AI summary

In an illustrative embodiment, watermark decoding reliability is increased, for images of watermarked objects captured at close distances, by reducing influence of pixel noise (e.g., shot noise). In the same or different embodiment, watermark decoding reliability is increased, for images of watermarked objects captured from far distances, by reducing image under-sampling. A particular implementation down-samples input imagery twice—a first time by a fixed factor, preparatory to performing an FFT, and a second time by a variable factor, preparatory to submitting the image for decoding, where the variable factor is determined using results from the FFT. A number of other features and arrangements are also detailed.