Krzysztof Klimaszewski

Distortions of synthesized views caused by compression of views and depth maps

The paper deals with prospective 3D video transmission systems that would use compression of both multiview video and depth maps. The paper addresses the problem of quality of views synthesized from other views transmitted together with depth information. For the state-of-the-art depth map estimation and view synthesize techniques, the paper proves that AVC/SVC-based Multiview Video Coding technique can be used for compression of both view pictures and depth maps. The paper reports extensive experiments where synthesized video quality has been estimated by use of both PSNR index and subjective assessment. Defined is the critical value of depth quantization parameter as a function of the reference view quantization parameter. For smaller depth map quantization parameters, depth map compression has negligible influence on fidelity of synthesized views.

Vehicle dimensions estimation scheme using AAM on stereoscopic video

Recently, stereoscopic video systems are studied in the context of many new applications. This paper addresses the question how the road traffic surveillance may benefit from stereoscopic video analysis. In particular, we propose a novel method for estimating vehicle dimensions using stereoscopic video analysis. This method is based on active appearance model (AAM), a technique already used, e.g. for face detection. Experimental results are provided in the paper in order to demonstrate satisfactory precision of the measurements.

Bitrate distribution of syntax elements in the HEVC encoded video

The paper focuses on two problems: 1) analysis of bitrate contribution of I and B frames in encoded HEVC data stream, and 2) analysis of distribution of HEVC syntax elements in I and B frames. The relationship between sizes of I and B frames located at a different levels in hierarchical coding scheme was experimentally determined, as well as contribution of HEVC syntax elements in encoded streams of I, B0, B1, B2, and B3 frames. The results are presented in the paper. All presented results concern a wide range of QP values in a video encoder.

Quantization optimization in multiview plus depth video coding

In the paper, novel methods for quality control in multiview with depth video compression are described. First, a simple steepest-descent-based algorithm for adjusting quantization parameters for texture and corresponding depth to obtain the maximal quality for a given bitrate is proposed. Then, experimental results are shown, basing on which a mathematical model for calculation of quantization parameters for the depth and texture is proposed. The paper also covers subject of coding depth with different resolution than the texture. The work is presented in context of the most contemporary compression methods related to AVC, but could also be easily adapted to upcoming 3D-video coding extensions of HEVC.

Enhancement of stereoscopic depth estimation by the use of motion information

The method presented in this paper uses motion information to complement the state-of-the-art depth estimation technique. The use of motion field correspondence between different views in the matching cost function for disparity computation is proposed. In addition, edges from motion maps are used to modify smoothing cost function in the algorithm in order to preserve sharp edges of moving objects and smooth transitions in the background or steady areas of depth map. Experimental results show that our modified algorithm significantly increases quality of depth maps in local areas. The technique is particularly interesting for applications where motion estimation is also needed for other purposes.

Analysis of Frame Partitioning in HEVC

The paper presents analysis of frame partitioning in the next generation video coding standard HEVC. Complex study on frequency of the particular coding unit, prediction unit and transform unit sizes selection made by the encoder compliant with HEVC technology is included. General conclusions based on extensive experiments for HD video sequences are presented. Such knowledge may be the first step to the development of more efficient mode selection algorithms.

Application of Epipolar Rectification Algorithm in 3D Television

The paper describes a method for rectification of video in 3D television parallel multi-camera systems. Using the camera calibration data gathered, a new coordinate system is calculated, in which virtual camera positions and orientations are calculated. A rectifying perspective transform is calculated that performs transformation from the real camera coordinate system to a new system. Transformed images correspond to images from virtual rectified camera setup. The results obtained using the method described are verified by computation of depth maps using the rectified video.

Encoding mode selection in HEVC with the use of noise reduction

This paper concerns optimization of encoding in HEVC. A novel method is proposed in which encoding modes, e.g. coding block structure, prediction types and motion vectors, are selected basing on noise-reduced version of the input sequence, while the content, e.g. transform coefficients, are coded basing on the unaltered input sequence. Although the proposed scheme involves encoding of two versions of the input sequence, the proposed realization ensures that the complexity is only negligibly larger than complexity of a single encoder. The proposal has been implemented and assessed. The experimental results show that the proposal provides up to 1.5% bitrate reduction while preserving the same video quality.

Homogenous HEVC video transcoding by transform coefficient removal

In this paper, a novel method of transcoding of HEVC encoded video is presented. The novel approach enables a very fast transcoding without the need for the image reconstruction. It is based on the principle of removing of the carefully selected coefficients from the bitstream. The removal of coefficients is done on the bitstream level and can easily be tailored to software as well as hardware implementations. The technique is able to provide a bitrate reduction in the order of up to 10%, with the image quality decrease of about 0.2–0.5dB.

Analysis of the complexity of the HEVC motion estimation

The paper presents analysis and comparison of complexity of selected algorithms of motion estimation used in video compression. With the use of own, highly optimized software implementation the authors explored complexity of the methods applied in the framework of the new High Efficiency Video Compression (HEVC) technology. The influence of many different factors on motion estimation complexity has been deeply studied, including the implementation technique, type of the algorithm, number of processor threads used, kind of metric of blocks similarity. The results obtained allowed to formulate guidelines and conclusions that may be useful for future implementation of motion estimation algorithms in context of HEVC encoders.