Global and local rate-distortion optimization for Lapped Biorthogonal Transform coding

It is a well-known fact that, in order to overcome annoying blocking artifacts, transforms with block-overlapping basis functions have been proposed for image coding. Typically in transform coding, the encoder determines the transform coefficient values by applying the forward transform followed by scalar quantization. In this paper we present an approach, how rate-distortion optimized Lapped Biorthogonal Transform (LBT) coefficient values can be determined by solving 1-regularized least squares problems. We compare a global version, where all the transform coefficients are obtained in one single optimization step, and a local version, where the optimization is done separately for each block, which results in losing optimality, but achieving highly reduced complexity. Our simulation results show gains of about 0.5 dB PSNR compared to ordinary forward transform and scalar quantization with only small losses (< 0.1 dB) for the local variant

Extended cross-component prediction in HEVC

With Version 2 of the high-efficiency video coding standard, a new compression efficiency tool targeting redundancies among color components is specified for all 4:4:4 profiles, and referred to as cross-component prediction (CCP). This paper describes and analyses two additional extensions to the specified CCP variant. In the first extension, an additional predictor is introduced. Particularly, beside the luma component, also the first chroma component can serve as a reference for prediction of the second chroma component. The second extension proposes a method for predicting the CCP model parameter from the statistics of already reconstructed neighboring blocks. A performance analysis of coding RGB content in different color representations is given in comparison with CCP and both extensions. Experimental results show that the proposed extensions can improve the compression efficiency effectively compared with CCP, when applied in the YCbCr domain

Compound Media Straming in Time

The widespread availability of networked multimedia potentials embedded in an infrastructure of qualitative superior kind gives rise to new approaches in the areas of teleteaching and Internet presentation: The distribution of professionally styled multimedia streams has fallen in the realm of possibility. This paper presents a prototype - both model and runtime environment - of a time directed media system treating any kind of presentational contribution as reusable media object components. The plug-in free runtime system is based on a database and allows for a flexible support of static media types as well as for easy extensions by streaming media servers. The technique of pluggable subservers is used to include a real-time video codec, based on a fast low complexity wavelet transformation and an highly efficient lossless precoding scheme using 'partitioning, aggregation, and conditional coding (PACC). The JAVA implementation enables real—time video streaming in CIF format on IP connections with low bandwidth (≈ 200kb/s)

Adaptive Temporal Scalability of H.264-compliant Video Conferencing in Heterogeneous Mobile Environments

In this paper, we present a multipoint video conferencing system that adapts to heterogeneous members including mobiles. The system is built upon a low complexity scalable extension of our H.264 codec DAVC, and a congestion-aware dynamic adaptation layer. Our temporally scaled video codec DSVC has the same RD performance as the non-scaled version with comparable configuration. We achieve this by QP cascading, i.e., assigning gradually refining quantization parameters to the declining temporal layers. We present and analyse a mobile-compliant version of DSVC at reduced complexity that still admits comparable performance. Finally, we report on early work of dynamic layer tuning. Derived of delay variation measures, senders exploit scalable video layering to adapt the video transmission to varying network conditions. Initial results indicate that video performance remains close to optimal