Hwang-Seok Oh

An efficient block-matching criterion for motion estimation and its VLSI implementation

The block-matching motion estimation is the most popular technique for motion compensated coding of image sequence. Due to the intensive computational requirement to perform motion estimation (ME) in real-time, application specific VLSI implementation of the ME is indispensable. We present a novel block-matching criterion for motion estimation called reduced bits mean absolute difference (RBMAD). By comparison with conventional schemes, our scheme reduces hardware requirement and increases the speed of computation in VLSI chip with acceptable video performance. We describe in detail the video performances of proposed criterion and conventional ones. We also show our VLSI implementation using the proposed scheme to compare the hardware requirement and operating speed with conventional ones. It is found that RBMAD using 4 bits has reasonable video performance with 57% less VLSI area and 34% faster, thus it is suitable for low cost applications of video coding.

Block-matching algorithm based on an adaptive reduction of the search area for motion estimation

The motion estimation and compensation technique is widely used for video coding applications but the real-time motion estimation is not easy due to its enormous computations. In this paper, a new adaptive reduction of search area for the block-matching algorithm is presented to reduce the computational complexity of the full search block-matching algorithm for low bit-rate video coding. The proposed method exploits the correlation of successive video frames and adjusts the size of search area depending on the displaced block difference and the block classification information in the previous frames of the block. Simulation results show that the proposed algorithm has similar mean square error performance to the full search block-matching algorithm but only requires less a half computational complexity than the full search algorithm.

Adaptive Video Watermarking Using Motion Information

This paper presents an adaptive video watermarking using motion information. Because video data have one more dimension than image data, simple adaptation of image watermarking method to video data would reveal some types of visual artifact such as flickering. In the proposed scheme, same watermark information is embedded for same region in each frame to decrease such visual artifact. For higher robustness and invisibility, watermarking strength is adjusted by motion information and region complexity.

Adaptive adjustment of the search window for block-matching algorithm with variable block size

The motion estimation and compensation technique is widely used for video coding applications but it is hard to implement the real-time video codec due to its enormous computations. An adaptive adjustment of the search window for the block-matching algorithm (BMA) with a variable block size is presented to reduce the computational complexity of full search BMA (FSBMA). The size of the search window is adjusted by using the block similarity and the displaced block difference (DBD). Experiments with test video sequences show that the presented scheme has good MSE performance and less complexity compared with FSBMA and other previous works.

Adaptive digital image watermarking using variable size of blocks in frequency domain

An adaptive digital image watermarking system considering of the human visual system (HVS) is presented in the frequency domain. The digital watermarks are embedded in selected discrete cosine transform (DCT) coefficients of variable size of blocks. To accommodate the HVS characteristics, the image is divided into variable size of blocks, where each block contains only homogeneous regions. The watermark is inserted by significantly changing the selected DCT coefficients of the block that has great variance or by slightly changing for the stationary block. It is shown that the proposed method has good robustness against several image processing operations without significant degradation of image quality by simulation using various test images.

A new block-matching algorithm based on an adaptive search area adjustment using spatio-temporal correlation

The motion estimation and compensation technique is widely used for video coding applications but the real-time motion estimation is not easy due to its enormous computations. In this paper, a new adaptive reduction of search area for the block-matching algorithm is presented to reduce the computational complexity of the full search block-matching algorithm for low bit-rate video coding. The proposed method exploits the correlation of successive video frames and adjusts the size of search area depending on the displaced block difference and the block classification information of the block in the previous frame. Simulation results show that the proposed algorithm has similar mean square error performance to the full search block-matching algorithm but only requires less a half computational complexity than the full search algorithm.

Human posture recognition using curved segments for image retrieval

This paper presents a human posture recognition method form a single image. We first segment an image into homogeneous regions and extract curve segments corresponding to human body parts. Each body part is considered as a 2D ribbon. From the smooth curve segments in skin regions, 2D ribbons are extracted and a human body model is constructed. We assign a predefined posture type to the image according to the constructed body model. For the user input query to retrieve images containing human of specific posture, the system convert the query to a body model. The body model is compared to other body models saved in the local storage of target images and images of good matches are retrieved. When a face detection result is available for the given image, it is also used to increase the reliability of body model. For the query human posture, our system retrieves images of the corresponding posture. As another application, the proposed method provides an initial location of a human body to track in a video sequence.

Adaptive rate control scheme for very low bit rate video coding

In video coding systems, an effective rate control method is one of the most important issues for a good video quality. This paper presents an adaptive rate control scheme based on buffer fullness, quantization, and buffer utilization for very low bit rate communication lines, such as 16 kbit/s, 32 kbit/s, and so on. The strategy is implemented by the H.263, which is a video coding algorithm for narrow band telecommunication channels up to 64 kbit/s recommended by the ITU-T SG15, to show the effectiveness. The simulation result shows that the suggested rate control scheme has better SNR performance and buffer utilization of the source coder than those of linear and non-linear buffer control strategies.

Adaptive bit-reduced mean absolute difference criterion for block-matching algorithm and its VLSI design

An adaptive bit-reduced mean absolute difference (ABRMAD) is presented as a criterion for the block-matching algorithm (BMA) to reduce the complexity of the very large scale integration (VLSI) imple- mentation and to improve the processing time. The ABRMAD uses the lower pixel resolution of the significant bits instead of full-resolution pixel values to estimate the motion vector (MV) by examining the pixels in a block. Simulation results show that the 4-bit ABRMAD has competitive mean square error (MSE) results and a half less hardware complexity than the mean absolute difference (MAD) criterion. It has also better characteristics in terms of both MSE performance and hardware com- plexity than the MiniMax criterion and has better MSE performance than difference pixel counting (DPC), binary block matching with edge map (BBME), and bit-plane matching (BPM) with the same number of bits.

Content-based retrieval system for image using human face information

The content-based image retrieval system framework using human-level features of image contents is presented. The system consists of face detection to locate the human faces within images, face recognition of the similarity measure between a query face and indexed faces within storage. Face detection and recognition techniques used in the system are very simple because short response time in interactive multimedia systems is essential. Color and elongated Gaussian filter response are used for face detection and dimple structural and normalized template matching are used for face similarities. Simulation results are summarized using restricted test images.