Klaus Illgner

Hierarchical coding of motion vector fields

Image sequences are mostly coded by motion compensated predictive coding. The motion vector field to be transmitted as side information is typically predictive coded. In this paper a new approach is presented for coding of motion vector fields at low bit rates (<64 kbit/s) more efficiently by applying a pyramid decomposition, which is encoded using zero-trees. The embedded coding of the pyramid allows for progressive transmission of the motion vectors and is well suited for source adaptive channel coding.

Spatially scalable video compression employing resolution pyramids

A spatially scalable video coding scheme for low bit rates is proposed. The codec is especially well suited for communications applications because it is based on motion-compensated predictive coding which provides the necessary low-delay property. The frames to be coded are decomposed into a Gaussian pyramid. Motion estimation and compensation are performed between corresponding pyramid levels of successive frames. We show that, to fulfill specific needs of spatial scalability, the motion compensation on each level must result in compatible prediction errors (displaced frame differences, DFD). Compatibility of the prediction errors means that the pyramid formed by independently obtained DFDs (the DFD pyramid) is close to a Gaussian pyramid decomposition of the DFD of the highest resolution level. From the DFD pyramid, a least squares Laplacian pyramid is derived, which is quantized and coded. The DFD encoder outputs an embedded bit stream. Thus, the coder control may truncate the bit stream at any point, and can keep a fixed rate. The motion vector fields obtained at the different resolution levels are also encoded by employing a pyramid approach. Simulation results show that the proposed coder achieves a coding gain compared to simulcast coding.

Wireless live streaming video of surgical operations: an evaluation of communication quality

We evaluated a mobile video system for surgical teleconsultation. A video streaming server in the operating room transmitted video and audio to a hand-held computer (personal digital assistant [PDA]) over a wireless local area network. Two groups of 20 surgeons (each with 12 qualified surgeons and eight surgeons between the 2nd and the 4th year of training) participated in the tests. For voice transmission, correct understanding of numbers was achieved in 100% of the cases (n = 1000) and 98% of medical terms (n = 400). The quality of the video displayed on the PDA was assessed by the recognition of different operating room scenarios. Only 62% (SD 17) of the structures were identified clearly on the hand-held device (n = 400). The accuracy improved to 78% (SD 15) (n = 400) if the same scenario was observed on a larger (50 cm) video screen (p < 0.001). Accuracy was significantly better if audio conversation was possible. The quality evaluation by the consultants showed that the PDA display size and quality were sufficient for clinical use.

Image segmentation using motion estimation

Publisher Summary This chapter presents an approach for segmenting frames of image sequences into homogeneously moving regions. The problem of estimating the segmentation of the image plane into regions based on motion is ill-posed. The segmentation depends on the motion description, which needs to be estimated as well and depends itself on the segmentation. The possible solutions depend on the type of motion description. Parametric motion descriptions with few parameters are too restrictive to represent complex motion. Therefore, assigning simple motion parameters to very small atom regions is more flexible. Homogeneity of the motion means, that the motion parameters of neighbored regions are similar, but not necessarily equal. The final segmentation is then a composition of these atom regions. The aim of the approach described in this section is to achieve suitable motion based segmentation with low computational complexity. As the aim is to achieve segmentation into homogeneously moving regions, the segmentation is restricted to using the motion vector field only. Therefore, there is no single parameter set to represent the motion of a region. By using a hierarchical approach a segmentation of increasing accuracy is obtained. Further advantages of this approach are robustness and low computational complexity.

Embedded Laplacian pyramid image coding using conditional arithmetic coding

A method for still image coding is proposed which allows for progressive transmission, because low detailed versions of the image can be reconstructed from a truncated bit stream. The proposed method is in its main aspects close to the classical pyramid approach of Burt and Adelson (1983). While retaining the main idea of using a Laplacian pyramid type decomposition, the new proposal differs in the filters employed for pyramid decomposition and in the bit allocation and quantization. The image is decomposed into an improved Laplacian pyramid. The pyramid is quantized and coded following a layered quantization approach together with a layered coding method based on conditional arithmetic coding. The encoder outputs an embedded bit stream. Thus the decoder may truncate the bit stream at any point, which results in a more or less detailed image. Besides this rate-distortion scalability the coder has a multiresolution property, due to the pyramid decomposition. An extension to hybrid video coding is also discussed.

Temporal video segmentation using global motion estimation and discrete curve evolution

The identification of syntactic or semantic temporal segments is an important process of video-content analysis. The paper proposes a temporal video segmentation method based on global motion in order to analyze meaningful temporal substructures of camera shots. To ensure that the detected segment optimally contributes to the shot global characteristic, the proposed method exploits a state-of-the-art discrete curve evolution. This technique leads to a subdivision of the global motion trajectory, where each segment of the subdivision has a constant relevant global motion. Experimental results based on standard test sequences acknowledge the method functionality, especially for shots characterized by pronounced camera motion.

Broadcast technologies for disseminating cultural heritage

This paper introduces the System for Advanced Multimedia Broadcast and IT Services (SAMBITS). It consists of a Studio, Server and TV Terminal system for broadcasting audio/video TV content enhanced by 3D graphics, Internet pages, database indexing and sub-image streaming. It describes two scenarios program for disseminating cultural heritage. The readers are invited to imagine how this system could be used to prepare programs for disseminating archaeology. The paper describes the Studio and Server Tools and the main functionality of the TV terminal. It describes the functionality of the terminal through the description of the scenario in conjunction with illustrative screen shots.

Multiresolution video compression: motion estimation and vector field coding

A multiresolution video coding scheme for very low bit rates is proposed, which is spatial scalable and thus allows easy adaptation to varying bandwidth conditions. Since the scheme is based on the hybrid coding principle it provides a low delay property making the codec well suited for communications applications. The frames to be coded are decomposed into a Gaussian-type pyramid. Motion estimation and compensation is performed between corresponding pyramid levels of successive frames such that the resulting prediction errors are close to a Gaussian pyramid decomposition of the prediction error at the highest resolution level. From this pyramid a Laplacian-type pyramid is derived and coded in an embedded fashion using conditioning contexts. The obtained motion vector fields at the different resolution levels form also a Laplacian-type pyramid which is encoded using zero-trees.

Motion estimation using segmented Gibbs-modeled vector fields

The approach described in this paper improves block-based motion estimation and compensation by introduction of a block segmentation dividing each block into two parts. For each block a segmentation pattern is derived from the motion vectors, which circumvents the transmission of the segmentation as side information. Motion vectors are estimated for both parts of a block. Although the number of motion vectors increases, the coding overhead can be kept sufficiently low by incorporating a Gibbs-criterion into the motion estimation criterion to trade off coding rate versus prediction error.