Dae-sung Cho

Interplane prediction for RGB video coding

This paper presents an efficient video coding method in RGB space. Generally RGB space is regarded as a bad space from a compression point of view. Each RGB component contains the color information along with luminance information. This redundancy degrades the coding efficiency. To exploit the intercolor redundancy, the RGB space is usually converted into another color space. But it inevitably causes color distortion due to the rounding operation involved. For professional applications it is essential to maintain the original color fidelity. To cope with these problems we propose an inter-plane prediction (IPP) that increases the coding efficiency in RGB space while avoiding color distortion. The proposed IPP exploits the redundancy of the residual images, which exists even after intra/inter prediction in MC-DCT based codec. The simulation results show that by applying the IPP to the MPEG-4 AVC/H.264 4:4:4 codec we can achieve up to 40% higher coding efficiency than that of the coding without IPP option. We also show there exists an achievable PSNR limit if color space conversion is involved. In other words, coding in a given space is important to keep the fidelity of the original data for professional applications.

A new color transform for RGB coding

This paper presents a new color transform (YSbSr) that increases the coding efficiency for RGB space by reducing the conversion error and coding error propagation that happen during the color space conversion. Traditionally the use of color transforms has been limited to maintain the compatibility with black-and-white transmission. But for high quality video for professional applications, the focus should change accordingly. Recently during the course of development for Professional Extensions of the MPEG-4 AVC H.264 standard, new color transforms have been proposed. These transforms are focusing on the decorrelation and reversibility using a lifting scheme for integer implementation. But in a real coding scenario, lossless coding is rare and coding error is inevitable. So we have to deal with the propagation of coding error due to the backward conversion to RGB space. Even though integer mapping is a charming factor, it is more desirable not to employ integer mapping if we lose the original goal, high decorrelation gain with small conversion error. Since the conversion equation takes up a very small portion of coder complexity, the difference between integer mappings and floating point operation is diluted. Based on this observation, we propose a new color transform that gives: high decorrelation gain with small rounding and conversion error. The simulation results show that we can achieve almost up to 2 dB gain compared with the traditional YCbCr color space using the proposed transform. It makes the proposed color transform a good candidate for applications that need to preserve the original color fidelity.

New algorithms for example-based super-resolution

This paper describes enhancements on example-based super-resolution. Example-based super resolution has the advantage that only one observation of the low-resolution image is required but reconstruction requires long processing time. We propose techniques to achieve faster operation and/or better quality by several modifications of previous techniques. We show some typical data as quantitative results also including video in electronic version.