M. Oguz Bici

A study on the effect of MPE-FEC for 3D video broadcasting over DVB-H

Wireless networks are often error prone due to factors such as multi-path fading and interferences. In addition, the channel conditions of these networks are often non-stationary, such that the available bandwidth and channel error rates are changing over time with large variations. Therefore, they present a challenge for error-resilient video transmission. In order to maintain satisfactory QoS, a number of technologies have been proposed targeting different layers of the networks. DVB-H uses FEC for error protection and comes with an optional FEC tool (MPE-FEC) at the link-layer. In this paper, we propose to use the a priori knowledge of the transmitted media and apply MPE-FEC intelligently to provide better robustness by so-called Unequal Error Protection (UEP) mechanism. Extensive simulation results are given to show the effect of MPE-FEC on 3D compressed video under different channel conditions.

Improved prediction methods for scalable predictive animated mesh compression

Animated meshes represented as sequences of static meshes sharing the same connectivity require efficient compression. Among the compression techniques, layered predictive coding methods efficiently encode the animated meshes in a structured way such that the successive reconstruction with an adaptable quality can be performed. The decoding quality heavily depends on how well the prediction is performed in the encoder. Due to this fact, in this paper, three novel prediction structures are proposed and integrated into a state of the art layered predictive coder. The proposed structures are based on weighted spatial prediction with its weighted refinement and angular relations of triangles between current and previous frames. The experimental results show that compared to the state of the art scalable predictive coder, up to 30% bitrate reductions can be achieved with the combination of proposed prediction schemes depending on the content and quantization level.

Wavelet-based multiple description coding of 3-D geometry

In this work, we present a multiple description coding (MDC) scheme for reliable transmission of compressed three dimensional (3-D) meshes. It trades off reconstruction quality for error resilience to provide the best expected reconstruction of 3-D mesh at the decoder side. The proposed scheme is based on multiresolution geometry compression achieved by using wavelet transform and modified SPIHT algorithm. The trees of wavelet coefficients are divided into sets. Each description contains the coarsest level mesh and a number of tree sets coded with different rates. The original 3-D geometry can be reconstructed with acceptable quality from any received description. More descriptions provide better reconstruction quality. The proposed algorithm provides flexible number of descriptions and is optimized for varying packet loss rates (PLR) and channel bandwidth.

Mobile 3D video broadcast

In this paper, we present a complete framework of an end-to-end error resilient transmission of 3D video over Digital Video Broadcasting - Handheld (DVB-H) and provide an extensive analysis of coding and transmission parameters. We perform the analysis for different coding and error resilience schemes using different contents coded at different bitrate levels. Throughout the experiments, we investigate the effects of video content type, video bitrate, coding method and unequal protection level for different channel conditions. The results show that Multi-view Coding (MVC) coding outperforms Simulcast and distribution of available bitrate between video quality and Forward Error Correction (FEC) protection is an important factor in different channel conditions.

Improved prediction for layered predictive animated mesh compression

In this paper, we deal with layered predictive compression of animated meshes represented by series of 3D static meshes with same connectivity. We propose two schemes to improve the prediction. First improvement is using weighted spatial prediction rather than averaging neighbor vertices. The second improvement is a novel predictor based on rotation angle of incident triangles in current and previous frames. The experimental results show that around 6–10 % bitrate reduction can be achieved by replacing the spatial prediction in the reference coder with the proposed weighted spatial prediction and 9–18 % bitrate reduction is possible with the proposed angle based predictor using weighted spatial prediction, depending on the content and quantization level.

Multiple description coding of animated meshes

In this paper, we propose three novel multiple description coding (MDC) methods for reliable transmission of compressed animated meshes represented by series of 3D static meshes with same connectivity. The proposed methods trade off reconstruction quality for error resilience to provide the best expected reconstruction of 3D mesh sequence at the decoder side. The methods are based on layer duplication and partitioning of the set of vertices of a scalable coded animated mesh by either spatial or temporal subsampling. Each partitioned set is encoded separately to generate independently decodable bitstreams or so-called descriptions. In addition, the proposed MDC methods can achieve varying redundancy allocations by including a number of encoded spatial or temporal layers from the other description. The algorithms are evaluated with redundancy-rate-distortion (RRD) curves and per-frame reconstruction analysis. RRD performances show that vertex partitioning-based MDC performs better at low redundancies for especially spatially dense models. Temporal subsampling-based MDC performs better at moderate redundancies as well as low redundancies for spatially coarse models. Layer duplication-based MDC can achieve the lowest redundancies with flexible redundancy allocation capability and can be designed to achieve the smallest variance of reconstruction quality between consecutive frames.

Multiple description coding of 3D dynamic meshes based on temporal subsampling

In this paper, we propose a Multiple Description Coding (MDC) method for reliable transmission of compressed time consistent 3D dynamic meshes. It trades off reconstruction quality for error resilience to provide the best expected reconstruction of 3D mesh sequence at the decoder side. The method is based on partitioning the mesh frames into two sets by temporal subsampling and encoding each set independently by a 3D dynamic mesh coder. The encoded independent bitstreams or so-called descriptions are transmitted independently. The 3D dynamic mesh coder is based on predictive coding with spatial and temporal layered decomposition. In addition, the proposed method allows for different redundancy allocations by including a number of encoded spatial layers of the frames in the other set. The algorithm is evaluated with redundancy-rate-distortion curves and it is shown that, when one of the descriptions is lost, acceptable quality can be achieved with around 50% redundancy.

Stereo video broadcast over DVB-H

This paper presents modelling and analysis of a mobile 3DTV broadcast system for handheld devices. The underlying technology behind our system is the DVB-H specification which brings ordinary TV broadcast services to battery-powered handheld receivers. In our system, we simulated the broadcast of stereo video content over DVB-H to mobile handheld devices with autostereoscopic displays. In this way, mobile users can watch 3D content without need for eyeglasses or any special equipment.

Vertex partitioning based Multiple Description Coding of 3D dynamic meshes

In this paper, we propose a Multiple Description Coding (MDC) method for reliable transmission of compressed time consistent 3D dynamic meshes. It trades off reconstruction quality for error resilience to provide the best expected reconstruction of 3D mesh sequence at the decoder side. The method is based on partitioning the mesh vertices into two sets and encoding each set independently by a 3D dynamic mesh coder. The encoded independent bitstreams or socalled descriptions are transmitted independently. The 3D dynamic mesh coder is based on predictive coding with spatial and temporal layered decomposition. In addition, the proposed method allows for different redundancy allocations by duplicating a number of encoded spatial layers in both sets. The algorithm is evaluated with redundancy-rate-distortion curves and flexible trade-off between redundancy and side distortions can be achieved.

Multiple Description Coding of 3D Meshes Based on Forward Error Correction

This work presents a multiple description coding (MDC) scheme for compressed three dimensional (3D) meshes based on forward error correction (FEC). It allows flexible allocation of coding redundancy for reliable transmission over error-prone channels. The proposed scheme is based on progressive geometry compression, which is performed by using wavelet transform and modified SPIHT algorithm. The proposed algorithm is optimized for varying packet loss rates (PLR) and channel bandwidth. Modeling distortion-rate function considerably decreases computational complexity of bit allocation.