Hye Soo Kim

Expert system for low frequency adaptive image watermarking: Using psychological experiments on human image perception

Abstract This paper proposes a new system for low frequency adaptive image watermarking based on the statistical data from psychological experiments on human image perception. The new approach can lead to a reduction of degrading the subjective image quality that often occurs when watermark is embedded into low frequency area. In order to reduce the degrading of image quality, the new approach determines the strength of watermark according to local image characteristics such as brightness and contrast. By conducting a behavioral experiment on human image fidelity based on the psycho-visual image association technique, we were able to infer the relationship between the watermark strength and the different levels of image brightness and contrast information. The exact watermark is extracted according to edge characteristics by adopting a so-called edge mask that exploits the coefficients of subbands in the subsampled discrete wavelet transform images. Thus, our new approach does not require original images for watermark. We also show the new approach is practically validated against some standard images.

Measurement Based Channel-Adaptive Video Streaming for Mobile Devices over Mobile WiMAX

The channel bandwidth variation and the disconnection during handoff are the most critical problems which degrade the video quality in wireless video streaming. To cope with these problems, we propose an efficient video streaming method in this paper, which does not only dynamically adjust the video transmission rate based on the channel bandwidth, but also minimize the error propagation during handoff. First, the channel bandwidth of the mobile worldwide interoperability for microwave access, called WiMAX, is estimated by analyzing channel parameters including the carrier to interference and noise ratio (CINR) and the handoff is detected by using the handoff occurrence message (HOM). Second, the streaming server adjusts the next transmission rate according to the estimated channel bandwidth to avoid the network congestion and performs the intra refresh method that inserts an intra frame (l-frame) right after handoff by using the HOM to reduce the error propagation effectively. Experimental results indicate that the proposed method can improve the performance of the video streaming over mobile WiMAX.

Efficient real-time frame layer rate control technique for low bit rate video over WLAN

A real-time frame-layer rate control algorithm is proposed for low bit rate video coding over IEEE 802.11 wireless local area network (WLAN). The proposed rate control method performs bit allocation at the frame level to minimize the average distortion over an entire sequence as well as variations in distortion between frames. A new frame-layer rate-distortion model is derived, and a non-iterative optimization method is used for low computational complexity. The proposed algorithm produces low encoding time delay, and is suitable for real-time low-complexity video encoder. Experimental results indicate that the proposed control method provides better visual and PSNR performance than the existing TMN8 rate control method.

Estimation-Based Interlayer Intra Prediction for Scalable Video Coding

The scalable video coding (SVC) standard adopts a simple interlayer intra prediction (ILIP) method for encoding scalable video sequences. In the conventional ILIP, a prediction signal for the macroblock (MB) of the enhancement layer (EL) is obtained by simply upsampling the colocated block of the base layer (BL). We propose an improved ILIP method by generalizing the original one adopted in the SVC standard. In the proposed ILIP method, the MB of the EL is predicted using all MBs of the BL. Experimental results show that the proposed algorithm can reduce the bit rate by 1.91% to 6.44%, as compared with the conventional ILIP, while the average PSNR is not decreased.

Dynamic GOP structure selection to support QoS in vertical handoff

This paper proposes a dynamic GOP structure selection method to provide seamless video streaming for vertical handoff in the heterogeneous wireless network. The proposed method dynamically changes the interval of I-pictures by using the received signal strength indication (RSSI) and the pilot strength (Ec/Io) in order to reduce error propagation due to packet losses. Thus, with the proposed method, the client can always receive the I-picture right after vertical handoff. Experimental results show that the proposed method can significantly reduce the video quality degradation caused by vertical handoff in the real-time video encoding applications.

Fast handoff scheme for seamless multimedia service in wireless LAN

In this paper, we propose a fast handoff method for seamless multimedia service in IEEE 802.11 WLAN. The proposed method uses an improved access point (AP) with additional radio frequency (RF) module, SNIFFER, monitoring the movement of the station (STA). By using the SNIFFER, the proposed method can completely remove the probe delay. Furthermore, we also propose an effective handoff decision method taking into account the quality of service (QoS) in the application layer. The proposed method uses packet loss information and the received signal strength indication (RSSI) for the handoff decision. Experimental results show that the proposed method can improve the performance of the seamless multimedia service by drastically reducing the handoff delay and packet loss.

Power-aware rate-control for QoS provisioning over CDMA networks

This paper presents a power-aware rate control method that dynamically adjusts the encoding bit rate according to the receiving power level of mobile stations (MSs) in CDMA network. The proposed rate-control method performs bit allocation at the video frame level using the estimated channel bit rate to minimize the average distortion over wireless video transmission. Experimental results show that the proposed method can significantly enhance the video quality in CDMA networks.

Seamless Video Streaming Technique Supporting Error Concealment for VOD Services in Vertical Handoff*This paper was presented at ITC-CSCC 2005, Session P5-57.

Vertical handoff is required to achieve anywhere and anytime internet access in the fourth generation (4G) network providing interoperability between universal mobile telecommunications system (UMTS) and wireless LAN (WLAN). However, video data can be lost due to latency caused by vertical handoff. To solve this problem, in this paper, we propose a video streaming technique supporting error concealment (EC) for video on demand (VOD) services that provides seamless playout at the client in vertical handoff. In the proposed method, the streaming server first predicts the client buffer status (CBS). Using the predicted CBS and the channel rate, the streaming server selects a proper video transmission method for vertical handoff between frame selective pre (FSP)-transmission and re-transmission. Performance evaluations are presented to demonstrate the effectiveness of the proposed method.

Channel-Aware V ideo Streaming for Mobile Devices over WiBro Network

This paper presents a channel-aware video streaming method that does not only adjust dynamically the target bit rate according to the channel condition but also minimize the error propagation at handoff. The proposed method performs adaptive bit rate allocation (ABA) by using the carrier to interference and noise ratio (CINR) to reduce the packet loss ratio (PLR) without wasting the channel resource. Moreover, adaptive intra refresh (AIR) is performed to reduce the error propagation when the handoff is occurred. Experimental results indicate that the proposed method can be successfully used for video streaming over WiBro networks.