Young-Ho Moon

Novel context template design scheme for lossless color halftone image compression

A novel template design algorithm is presented for lossless compression of color halftone images. First, we extract the line pattern in the neighbor local region of each bi-level pixel. Then, the representative line pattern is evaluated from these obtained lines, using the least square error minimization. According to the evaluated line pattern and two design constraints, therefore, the context template is shaped. With the designed template, finally, each color channel image is compressed by a context-based binary arithmetic encoder. Based on the adaptiveness of the template to the input image, the proposed templates yield better compression performance than the conventional JBIG templates, which saves 35% of the JBIG bitstream.

Lossless image compression using valley transform

In this paper, a novel geometric transform, called the valley transform (VT), is proposed for robust compression of noisy images. The VT employs a nonlinear transform to convert random signals into regular ones. The proposed VT is able to change random pixels to regular one. For testing the compression performance, the VT is combined with the SPHIT method. The VT yields slightly better performance than the conventional image codecs such as JBIG, HD-photo and H.264 intra method in the lower bit-plane image compression.

Local interpolation filter estimation for fractional-pel displacement vector in video coding

ISO/IEC Motion Picture Experts Group (MPEG) and ITU-T Video Coding Experts Group (VCEG) have collaborated for development of new international video coding standard with high coding efficiency and network friendly video representation features. In 2003, JVT (collaboration group of MPEG and VCEG) published international standard H.264/MPEG-4 AVC which is the state of the art video coding technology. Several major technical progresses including precise fractional-pel displacement vector resolution with pre-fixed interpolation filter let H.264/MPEG-4 AVC have superior video coding efficiency compared to the previous standards such as MPEG-4, H.263 and etc. For recent years, many researches on interpolation filter for fractional-pel displacement vector have shown possibility for further improvements of video coding efficiency. Most investigations are on improvement of pre-fixed interpolation filters by transmitting texture dependent interpolation filter coefficients to decoder side. In this paper, we introduce a new approach for improvement of pre-fixed interpolation filter without transmitting filter information to decoder side, named as local interpolation filter estimation (LIFE). For generation of prediction signal with fractional-pel displacement vector, a local interpolation filter is estimated by exploitation of previously decoded spatial neighboring texture. Experimental results showed that we could get about 2 13% bit saving with LIFE compared to H.264 High Profile low delay condition.