Seong-Whan Kim

Perceptually tuned robust watermarking scheme for digital images

In this paper, we present a digital image watermarking scheme that uses both human visual system and statistical properties. The scheme places watermark in discrete cosine transform (DCT) domain and spreads the watermark effect on the entire image. We have compared our proposed scheme with two other popular schemes and shown that our proposed scheme yields better results in terms of transparency, robustness and maximal capacity requirements.

Perceptually tuned robust watermarking scheme for digital video using motion entropy masking

We present a watermarking scheme for digital videos that are based on human visual system characteristics. Our watermarking scheme inserts perceptually invisible watermark in the discrete cosine transform (DCT) domain. We have shown that the proposed scheme provides better results than two other popular schemes both in transparency and robustness.

Perceptually tuned video watermarking scheme using motion entropy masking

We present a watermarking scheme for digital videos that are based on the human visual system characteristics. Our watermarking scheme inserts a perceptually invisible watermark in the discrete cosine transform (DCT) domain. We have shown that the proposed scheme provides better results than two other popular schemes both in transparency and robustness.

A Gradient image dependent fragile watermarking for improved security and localization

Most fragile watermarking techniques are block-wise independent based schemes. They are either vulnerable to vector quantization (VQ) attack or sacrifice localization accuracy to improve security. This paper presents a gradient image dependent fragile watermarking scheme, which thwarts VQ attack while providing superior localization properties. The proposed technique provides distinct input keys for each image block from a large (1024! - 8770-bits entries) key space, a master key, a session key and block-wise permutated versions of a gradient image. The watermarking scheme requires only the master key (one time exchange) and the session key (each session) to be exchanged between the communication parties securely. Analysis and experimental results indicate that the proposed method possess better authentication and tamper detection capabilities compared to many other fragile watermarking schemes available in the literature. It can also be seen that the proposed scheme is suitable for both digital images and video.

Design and Implementation of AR Model based Automatic Identification and Restoration Scheme for Line Scratches in Old Films

Old archived film shows two major defects: line scratch and blobs. In this paper, we present a design and implementation of an automatic video restoration system for line scratches observed in archived film. We use autoregressive (AR) image model because we can make stochastic and specifically autoregressive image generation process with our PAST-PRESENT model and Sampling Pattern. We designed locality maximizing scanning pattern, which can generate nearly stationary time-like series of pixels, which is a strong requirement for a stochastic series to be autoregressive. The sampled pixel series undergoes filtering and model fitting using Durbin-Levinson algorithm before interpolation process. We designed three-stage film restoration system, which includes (1) film acquisition from VHS tapes, (2) simple line scratch detection and restoration, and (3) manual blob identification and sophisticated inpainting scheme. We implemented film acquisition and simple inpainting scheme on Texas Instruments DSP board TMS320DM642 EVM, and implemented our AR inpainting scheme on PC for sophisticated restoration. We experimented our scheme with two old Korean films: Viva Freedom and Robot Tae-Kwon-V, and the experimental results show that our scheme improves Bertalmio`s scheme for subjective quality (MOS), objective quality (PSNR), and especially restoration ratio (RR), which reflects how much similar to the manual inpainting results.

An Entropy Masking Model for Image and Video Watermarking

We present a new watermark design tool for digital images and digital videos that are based on human visual system (HVS) characteristics. In this tool, basic mechanisms (inhibitory and excitatory behaviour of cells) of HVS are used to determine image dependent upper bound values on watermark insertion. This allows us to insert maximai allowable transparent watermark, which in turn is extremely hard to attack with common image processing, Motion Picture Experts Group (MPEG) compression. As the number of details (e.g. edges) increases in an image, the HVS decrease its sensitivity to the details. In the same manner, as the number of motion increases in a video signal, the HVS decrease its sensitivity to the motions. We model this decreased sensitivity to the details and motions as an (motion) entropy masking. Entropy masking model can be efficiently used to increase the robustness of image and video watermarks. We have shown that our entropy-masking model provides watermark scheme with increased transparency and henceforth increased robustness.

MPEG Compliant Joint Source/Channel Coding using DCT and Substream Scheduling for Packet Networks

QoS-guarantee in real-time communication for multimedia applications is significantly important. An architectural framework for multimedia networks based on substreams or flows is effectively exploited for combining source and channel coding for multimedia data. But the existing frame by frame approach which includes Moving Pictures Expert Group (MPEG) cannot be neglected because it is a standard. In this paper, firstly, we designed an MPEG transcoder which converts an MPEG coded stream into variable rate packet sequences to be used for our joint source/channel coding (JSCC) scheme. Secondly, we designed a classification scheme to partition the packet stream into multiple substreams which have their own Quality of Service (QoS) requirements. Finally, we designed a management (reservation and scheduling) scheme for substreams to support better perceptual video quality such as the bound of end-to-end jitter. We have shown that our JSCC scheme is better than two other popular techniques by simulation and real video experiments on the TCP/IP environment.

Video coding with wavelet transform on the very-low-bit-rate communication channel

In this paper, we present a moving image coding system which uses wavelet transform for the videophone on a very low bit rate communication channel (10 K bps PSTN). There are two requirements for our coding system: the good subjective quality for low bit rate coding and the suitability for progressive transmission. To satisfy the requirements, we use multifrequency motion estimation which estimates motion for each frequency bands. After the motion estimation, we can assign less bits to the motion estimation error in the high frequency bands because the human is insensitive to the change in high frequency components in the case of moving image. The experimental results confirm that our approach out-performs discrete cosine transform coding schemes in terms of the subjective quality because there are no blocking effects, and moreover, the wavelet transform in the approach supports the progressive transmission in itself.