Woongho Lee

Fast panoramic image generation method using morphological corner detection

We present a method of building a panoramic image from adjacent images. The panoramic image is constructed using several images taken by adjacent cameras or parsed from a video, and used for photogrammetry or many computer graphic applications. The perspective transformation, which is estimated from the appropriate corresponding pairs of images, can be used to construct the panoramic image without unwarranted distortion. We used the comer points for the corresponding features, and morphological structures were utilized for fast and robust comer detection. We used the criterion of the comer strength, which guarantees the robust detection of the comer in most situations. For the transformation, 8 parameters were estimated from perspective equations, and bilinear color blending was used to construct a seamless panoramic video. The experiments showed that the proposed method yields fast results with good quality under various conditions.

Fast panoramic video generation method using morphological corner detection

We present a method for building panoramic video for Video GIS. The panoramic video is composed of several images taken by adjacent cameras. The perspective transformation, which estimated from the appropriate corresponding pairs between the images, can construct the panoramic video without unwilling distortions. We use corner points for the corresponding feature, and morphological structures are utilized for fast and robust corner detection. We propose a criterion method of corner strength, which guarantees the robust detection of corner in any situations. For the transformation, 8-parameters are estimated from perspective equations, and bilinear color blending is used to construct a seamless panoramic video. Experiments show that our method yields good results in various conditions.

New intra luma prediction mode in H.264/AVC using collocated weighted chroma pixel value

Intra prediction in H.264/AVC uses 9 modes in 4×4 luma block, 4 in 16×16 luma and 8×8 chroma blocks. Intra prediction modes utilize similarity of current macroblock with pre-encoded neighboring macroblocks and directionality of image in pixel domain. Therefore its coding efficiency in H.264/AVC is improved compared to the conventional video codecs such as MPEG-2 and MPEG-4. However coding efficiency in intra-coded frame is much lower compared to that of inter slice since the intra prediction modes use only limited neighboring macro blocks and then to obtain good matched reference block image using intra prediction may be more difficult than inter prediction. Therefore for higher coding efficiency, it is very important to get good matched prediction block in a given envirionment. In general video codec which uses general 4:2:0 YCbCr format, overall coding efficiency issue is mainly focused on luma relative to chroma components. In this paper, we propose additional intra luma prediction mode using collocated chroma pixels and weight values. The proposed method utilizes collocated chroma macroblocks as reference image for more efficient intra luma prediction.

Fast intra mode decision algorithm of H.264/AVC

Intra prediction coding is one of the many coding-efficiency oriented tools of H.264/AVC, but it requires high computational complexity. Many fast intra coding algorithms have been proposed to reduce the computational complexity of intra prediction, but most of them have been focused on the mode decision methods themselves. In this paper, we propose a fast algorithm in which new intra modes are substituted for certain of the conventional intra modes, so that the number of intra modes can be reduced. The proposed intra modes, namely the weighted mean and median modes, can effectively represent the directions of a block in a frame. The simulation results showed that the proposed method could reduce the encoding time of the overall sequence by about 11 % and that of the I-frames by about 28%, without any noticeable degradation of the coding efficiency

Reduction of mode decision complexity in H.264/AVC using adaptive selection of reference frame and intra prediction mode

Rate-constrained coding is one of the many coding-efficiency oriented tools of H.264/AVC, however, the mode decision process of Rate Distortion Optimization (RDO), is characterized by high computational complexity. Many fast mode decision algorithms have been proposed to reduce the computational complexity of mode decision. In this paper, two algorithms are proposed for reduction of mode decision in H.264/AVC, fast reference frame selection and selective intra prediction mode decision. Fast reference frame selection is efficient for inter predication, and selective intra prediction mode decision can effectively reduce excessive calculation load of intra prediction mode decision. The simulation results demonstrated that the proposed two methods applied together could reduce the encoding time of the overall sequences by an average of 44.63%, without any noticeable degradation in coding efficiency.