Abstract

This paper presents a new missing data detection algorithm that is robust to pathological motion (PM). PM causes clean image data to be misdiagnosed as missing data, resulting in damage to the image during restoration. The proposed algorithm uses a probabilistic framework to jointly detect PM and missing data. It builds on an existing technique of using five frames for detection instead of the standard three frames. This allows the temporally impulsive intensity profile of blotches to be distinguished from the quasiperiodic profile of PM. Another diagnostic for PM is defined on the motion fields of the five-frame window. This follows the observation that PM results in motion fields which are not smooth. A ground truth comparison with standard missing data detectors shows that the proposed algorithm dramatically reduces the number of falsely detected missing data regions. It is also shown to reduce image damage during missing data treatment.

Highlights

  • Missing data treatment is an important process in the digital restoration of archived media

  • Most blotch detection algorithms are derived from the assumption that if a blotch is present at a particular location in a frame, no blotches are present at the same point in neighbouring frames

  • Examples of detectors using a three-frame window include the deterministic spike detection index (SDI) [1, 2] and rank order distance (ROD) [3, 4] detectors, which apply deterministic thresholds to the displaced frame difference (DFD) to detect discontinuities, and the probabilistic Morris [2, 5] and blotch Markov random field (MRF) [6] algorithms, which allow for the inclusion of prior knowledge of the result into the decision

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Summary

INTRODUCTION

Missing data treatment is an important process in the digital restoration of archived media. The state-of-the art motion estimators can robustly estimate the most common motion patterns, there are complex motion patterns which cannot be estimated accurately This complex motion is referred to as pathological motion (PM) and can lead to true image data being detected as a blotch (see Figure 1). The algorithm is made more robust by preventing PM regions being detected as blotches, thereby preventing damage to image data during restoration of dirty sequences. A five-frame window is used instead of the standard three frames This allows blotches to be distinguished from long term forms of PM, since blotches have a temporally impulsive intensity profile and PM often causes the intensity to vary in a periodic manner (see Figure 2). The paper concludes with a discussion of the algorithm, outlining areas for future development

REVIEW OF PM DETECTION ALGORITHMS
ALGORITHM OVERVIEW
Temporal discontinuity-based detection
Motion field smoothness based detection
PROBABILISTIC FRAMEWORK
Temporal discontinuity likelihood
Motion estimation
The likelihood expression
Divergence likelihood
The smoothness prior
The PM bias
Multiresolution
RESULTS
Ground truth acquisition
Configuration of the proposed algorithm
ROC plots
Visual evaluation
Implementation of the algorithm
Algorithm evaluation
Comparison with other missing data detectors
Detector configuration
Comparison with the conventional detectors
Comparison with the Bornard algorithm
Blotch restoration using the proposed algorithm
Computational complexity
FINAL COMMENTS
Full Text
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