Yang-lim Choi

Video Super-Resolution Algorithm Using Bi-Directional Overlapped Block Motion Compensation and On-the-Fly Dictionary Training

This paper presents a video super-resolution algorithm to interpolate an arbitrary frame in a low resolution video sequence from sparsely existing high resolution key-frames. First, a hierarchical block-based motion estimation is performed between an input and low resolution key-frames. If the motion-compensated error is small, then an input low resolution patch is temporally super-resolved via bi-directional overlapped block motion compensation. Otherwise, the input patch is spatially super-resolved using the dictionary that has been already learned from the low resolution and its corresponding high resolution key-frame pair. Finally, possible blocking artifacts between temporally super-resolved patches and spatially super-resolved patches are concealed using a specific de-blocking filter. The experimental results show that the proposed algorithm provides significantly better subjective visual quality as well as higher peak-to-peak signal-to-noise ratio than those by previous interpolation algorithms.

Key frame-based video super-resolution using bi-directional overlapped block motion compensation and trained dictionary

This paper presents a video super-resolution algorithm to interpolate an arbitrary frame in a low resolution video sequence from sparsely existing high resolution key pictures. Firstly, hierarchical motion estimation is performed between the input and the key low resolution frames on a patch basis. If motion-compensated error is small, an input LR patch is super-resolved by bi-directional overlapped block motion compensation. Otherwise, the input patch is spatially super-resolved using the dictionary which is learned from the key low resolution and its corresponding high resolution pictures beforehand. Finally, possible blocking artifacts between a motion-compensated patch and a spatially super-resolved patch are concealed using a specific de-blocking process. Experimental results show that the proposed algorithm provides significantly better subjective visual quality as well as objective quality than previous interpolation algorithms.

High-resolution image scaler using hierarchical motion estimation and overlapped block motion compensation

This paper presents a motion-compensated scaler to interpolate an arbitrary frame in a low resolution video sequence by using sparsely existing high resolution key frames. In order to minimize visually annoying blocking artifact caused by block motion compensation, hierarchical motion estimation is bi-directionally performed for forward and backward key frames. Also, bi-directional overlapped block motion compensation based on the predicted motion vectors is applied to the high resolution key frames. Simulation results show that the proposed algorithm provides significantly better subjective visual quality as well as higher PSNR than previous interpolation algorithms. The proposed algorithm can provide a differentiated functionality to cutting-edge digital cameras, camcorders, etc.

Video deblurring algorithm using an adjacent unblurred frame

Blurred frames may sparsely exist in a video sequence acquired by digital camcorder or digital camera. In order to remove the visually annoying artifact due to those blurred frames, this paper presents a novel motion deblurring algorithm where a blurred frame can be reconstructed utilizing adjacent unblurred frames. Firstly, a motion-compensated predictor of the blurred frame is derived from its neighboring unblurred frame using motion estimation. Then, an accurate blur kernel, which is difficult to obtain from a single blurred frame, is computed using both the predictor and the blurred frame. Next, again using those both frames, a residual deconvolution is proposed to reduce ringing artifacts inherent to conventional deconvolution. Simulation results show that the proposed algorithm provides superior deblurring results over conventional deblurring algorithms while preserving details with reduced ringing artifacts.

Alternating line high dynamic range imaging

In this paper, a novel method of improving dynamic range of imaging device is proposed. Unlike multi-capture HDR methods, the suggested method requires only a small modification to existing CMOS imaging sensor. By changing exposure time line by line, one can obtain a multi-exposure image in a single capture of an image. With such captured image, digital image processing algorithms are applied to recover the lost vertical resolution with minimal degradation. This paper will cover overall system issues as well as detailed description of the algorithms applied to recover high dynamic range image.

3D perception enhancement using depth map based color processing

The color, contrast and detail of an object in focus are increased, whereas those of a background are decreased based on the depth map for simulating atmospheric perspective and proximity luminance.

Consideration of illuminant independence in MPEG-7 color descriptors

In this paper, we demonstrate the retrieval performance of the color descriptors in ISO/IEC International standard (i.e., MPEG-7 Visual) against the images taken under various lighting conditions. A simple and effective method for compensating illumination variation is proposed. The method proposed is proven to be useful by testing images from laboratory and outside taken under many different lighting conditions using cameras with different white balance settings.