Sea-Nae Park

An efficienct rate-control algorithm for multi-view video coding

In this paper, we propose an efficient rate-control algorithm which considers characteristics of multi-view video coding (MVC). A rate control algorithm is one of the most important elements of video coding. There are many existing algorithms to control the bit rate but they are designed for single-view video coding. The rate control algorithm for MVC should be also conducted at view level. Conventional rate-control algorithms for single view videos do not use QP values of B frames in computing a GOP initial QP. However, we have to take into account QP values of B frames because the MVC has many B views which are composed of only B frames. In addition, other views also have many B frames because the MVC employ the hierarchical B for coding efficiency. In the proposed algorithm, initial QP of GOP should be computed with QP values of B frames. In our research, the proposed algorithm can allocate proper bitrates for B views which are composed of only B frames and QP values of B frames can affect the initial QP of GOP. The proposed method can control total bitrate of multiple views to be acquired and displayed at the same time. In our experimentation, we found that the proposed method can control bitrates for all the views according to target bitrates

Side information generation using adaptive search range for distributed video coding

In this paper, we propose a new side information generation (SIG) method which is applicable to distributed video coding (DVC). The proposed method adaptively changes a search range depending on a confidence level in hierarchical motion estimation (ME) and reconstructs the hole regions using the proposed uni-directional prediction and linear interpolation. In order to improve reliability of the hierarchical ME, ME for each block is performed in descending order of block variance values. Also, in order to alleviate errors from inaccurate motion vector (MV) estimation, search range is adaptively adjusted according to reliability of ME. Experimental results show that the proposed algorithm is better than several conventional methods for DVC. We also found that block artifacts and blur artifacts are significantly diminished by the proposed algorithm.

View-dependency video coding for asymmetric resolution stereoscopic views

We propose an asymmetric-resolution stereoscopic video codec that can be used for commercially available stereo displays. Currently, most stereo video displays are designed for displaying not only stereo video but also conventional single-view video in order to make them compatible to single-view video services. In these systems, the resolution of each input video for stereo mode is half the input resolution for a single-view mode. We propose a stereoscopic video codec to support both single-view and stereo-view services by encoding full-resolution left images and horizontally downsampled right images. However, it is not possible to employ the conventional disparity estimation between the two views because the resolution of the left image is different from that of the corresponding right image. So we propose a stereoscopic video codec based on a new disparity estimation/compensation method that makes use of all the information of the left reference image without downsampling. We achieved a 0.5- to 0.8-dB coding gain with the proposed stereoscopic codec, compared with several conventional stereoscopic coding algorithms.

Distributed video coding based on adaptive slice size using received motion vectors

In this paper, we propose a new distributed video coding (DVC) method based on adaptive slice size using received motion vectors (MVs). In the proposed algorithm, the MVs estimated at a DVC decoder are transmitted to a corresponding encoder. In the proposed encoder, a predicted side information (PSI) is reconstructed with the transmitted MVs and key frames. Therefore, the PSI can be generated same to side information (SI) at the decoder. We can, also, calculate an exact crossover probability between the SI and original input frame using PSI and the original frame. As a result, the proposed method can transmit minimum parity bits to maximize error correction ability of a channel decoder with minimal computational complexity. Experimental results show that the proposed algorithm is better than several conventional DVC methods.

Residual signal compression based on the blind signal decomposition for video coding

In this paper, a new residual signal compression method is proposed based on the blind signal decomposition for video coding. Blind signal decomposition is derived based on the fact that most of the natural signals in the real world could be decomposed into their basis signals and their weight values used in the composition process. In the proposed video coding system, composite data generated by adding two or more blocks are coded. Then the proposed decoder parses the coded bitstream and reconstructs the composite residual. The reconstructed composite residual is decomposed into the original residual blocks based on the blind signal decomposition. In the proposed system, the blind source separation is selectively used, depending on the performance of source separation. It is found that we can achieve approximately 2 ∼ 3dB gain by embedding our algorithm into an MPEG-4 baseline encoder.

Distributed Video Coding for Illumination Compensation of Multi-view Video

In this paper, we propose an improved distributed multi-view video coding method that is robust to illumination changes among different views. The use of view dependency is not effective for multi-view video because each view has different intrinsic and extrinsic camera parameters. In this paper, a modified distributed multi-view coding method is presented that applies illumination compensation when generating side information. The proposed encoder codes DC values of discrete cosine transform (DCT) coefficients separately by entropy coding. The proposed decoder can generate more accurate side information by using the transmitted DC coefficients to compensate for illumination changes. Furthermore, AC coefficients are coded with conventional entropy or channel coders depending on the frequency band. We found that the proposed algorithm is about 0.1~0.5 ㏈ better than conventional algorithms.

Heterogeneous Resolution Stereo Video Coding System

In this paper, we propose an effective stereo-view video coding method that considers stereo-view and displayer characteristics. Current many stereo video displayers are designed for not only stereo display but also conventional single view display. In these systems, the resolution of two input videos for a stereo mode is half of that of single view for compatibility with conventional single view video services. In this raper, we propose a stereo video codec to deal with both single view and stereo view services by encoding whole left image and down-sampled right image. However, direct disparity estimation is not possible between two views because the resolution of a left image is different from that of the corresponding right image. So, we propose a disparity estimation method to make use of full information of the left reference image without down-sampling. In experimental result, we achieved coding gain, compared with several conventional algorithms.