Yongjin Cho

Bit Allocation for Spatial Scalability Coding of H.264/SVC With Dependent Rate-Distortion Analysis

We propose a model-based spatial layer bit allocation algorithm for H.264/scalable video coding (SVC) in this paper. The challenge of this problem lies in the fact that the rate-distortion (R-D) behavior of an enhancement layer is dependent on its preceding layers because of inter-layer prediction. To solve it, we first focus on the case of two spatial layers, derive the distortion and rate models of the dependent layer analytically, and develop a low-complexity bit allocation algorithm. It is shown by experimental results that the proposed two-layer bit allocation algorithm can achieve the coding performance close to the optimal R-D performance based on the full search method. Then, we extend this result to multilayer bit allocation by performing the two-layer allocation scheme recursively. Finally, we compare the performance of group of pictures-based and frame-based spatial layer bit allocation schemes at a fixed temporal resolution. The superior performance of the proposed spatial layer bit allocation algorithm is demonstrated using Joint Scalable Video Model reference software algorithm and two prior H.264/SVC rate control algorithms as the benchmarks.

H.264/SVC temporal bit allocation with dependent distortion model

The bit allocation problem for hierarchical B-pictures in H.264/SVC is studied with a GOP-based dependent distortion model in this work. Inter-dependency between temporal layers of H.264/SVC is often neglected because of the complexity involved, which often leads to poorer rate control performance. To address this shortcoming, we propose a distortion model that takes inter-dependency into consideration while preserving the low complexity of the encoding process. It is demonstrated by experimental results that the new distortion model results in a highly efficient bit allocation scheme, which outperforms the rate control algorithm in the JSVM 9.12 reference codec by a significant margin.

Cross-Layer Design for Wireless Video Streaming

We present a cross-layer approach to the design of a wireless video streaming system, which includes the development of an adaptive radio link buffer and congestion control algorithm and the adoption of the H.264/SVC scalable video format. The proposed system performs a group-of-pictures (GOP) based post-channel adaptation, which does not require the channel status information at the media server. Video packets are prioritized in a GOP-by-GOP manner based on the dependence relation within a GOP. We employ H.264/SVC for the video stream preparation to provide the flexibility and adaptability of compressed video data. The priority information is conveyed in the header extension of the network abstraction layer unit (NALU) of H.264/SVC, which is parsed by a media aware network element (MANE) to realize an efficient transmission and congestion control. The performance of the proposed algorithm is verified by the computer simulation.

GOP-based Rate Control for H.264/SVC with Hierarchical B-pictures

A GOP-based rate control algorithm for hierarchical B-pictures in H.264/SVC is proposed in this work. The problem is firstly formulated as a bit allocation problem among different temporal layers. Due to the dependency of these layers, we propose a Q-selection tree solution framework. The monotonicity property is exploited to prune the Q-selection tree. Then, the rate-distortion (R-D) data is calculated at a selected set of leaf nodes in any admissible Q-selection tree. The R-D data of other leaf nodes are interpolated using the log-linearity property of a local R-D model. It is shown by experiments that the proposed algorithm achieves a significant coding gain improvement at different target bit rates.

Joint quality-temporal (Q-T) bit allocation for H.264/SVC

A joint quality-temporal (Q-T) bit allocation scheme is proposed for H.264/SVC in this work. First, rate and distortion (R-D) models for dependent quality layers are derived, where the complex inter-layer dependency is considered. Then, the joint Q-T bit allocation problem is formulated as an optimization problem using the Lagrange method and solved numerically with the derived R-D models. As a result, we develop a low-complexity bit allocation scheme for the joint Q-T scalability of H.264/SVC. It is demonstrated by experimental results that the new R-D models results in a highly efficient bit allocation scheme, which outperforms the JSVM benchmark by a significant margin.

Dependent R/D Modeling Techniques and Joint T-Q Layer Bit Allocation for H.264/SVC

We investigate dependent rate/distortion (R/D) modeling techniques for H.264/SVC videos. We introduce a self-domain (S-domain) analysis method for characterizing the dependent R/D behaviors, where the R/D characteristics of a base layer are employed as the observation domain for those of dependent layers. Based on S-domain observations, we propose empirical dependent R/D models and analyze physical implications of the proposed models. As an application of the proposed R/D models, we examine a joint temporal-quality layer bit allocation algorithm formulated as a Lagrange optimization problem. The proposed R/D models enable us to derive an analytical solution to the joint optimization problem. Finally, it is demonstrated by experimental results that our bit allocation algorithm outperforms JSVM benchmark by a significant margin (10%-20%) at various bit rates.

Bit allocation for spatial scalability in H.264/SVC

We propose a model-based spatial layer bit allocation algorithm for H.264/SVC in this work. The spatial scalability of H.264/SVC is achieved by a multi-layer approach, where an enhancement layer is bound by the dependency on its preceding layers. The inter-layer dependency is decoupled in our analysis by a careful examination of the signal flow in the H.264/SVC encoder. We show that the rate and the distortion (R-D) characteristics of a dependent layer can be represented by a number of independent functions with a group of pictures (GOP) as a basic coding unit. Finally, a low complexity spatial layer bit allocation scheme is developed using the proposed GOP-based R-D models. It is shown by experimental results that our proposed bit allocation algorithm can achieve the coding performance close to the optimal R-D performance of full search and is significantly improved from current reference software JSVM.

A Simplified Rate Control Scheme for Non-Conversational H.264 Video

In this work, a simplified rate control algorithm is proposed for non-conversational H.264 video applications. When a GOP (group of pictures) structure is imposed on an encoded video, a bit rate control and a bit allocation among frames are two important components of a rate control algorithm. We employ a GOP rate model and the monotonicity property to address the bit rate control and the frame-layer bit allocation problem, respectively. Since the proposed algorithm employs only a GOP rate model, the rate control mechanism can be greatly simplified while it achieves better video quality as compared with that in the H.264 JM8.6 reference encoder.

Bit allocation for joint spatial-quality scalability in H.264/SVC

In this work, we propose a model-based layer bit allocation algorithm for joint spatial-quality (S-Q) scalability in H.264/SVC. The complicated inter-layer dependency is decoupled by the proposed spatial and quality rate and distortion (R-D) models. We show that the R-D characteristics of a dependent layer can be represented by a number of independent functions with GOP as a basic coding unit. Then, the joint bit allocation problem is formulated as a two-step optimization problem by the Lagrangian multiplier method, which can be numerically solved using the proposed R-D models. Finally, we develop a low-complexity bit allocation algorithm for the combined spatial and quality scalability in H.264/SVC. It is shown by experimental results that our proposed bit allocation algorithm achieves the coding performance significantly improved from current reference software JSVM.

Single pass dependent bit allocation for H.264 temporal scalability

In this paper, we propose a single-pass dependent bit allocation algorithm for H.264/SVC hierarchical B-pictures. To develop a practical bit allocation algorithm, we use the number of skipped blocks and the ratio of the mean absolute difference (MAD) as features to measure the inter-layer signal dependence of input video signals. The proposed algorithm performs bit allocation at the target bit rate with two steps: the group-of-picture (GOP) based rate control and adaptive temporal layer quantization parameter (QP) decision. The superior performance of the proposed algorithm is demonstrated by experimental results, which is compared with two other one-pass bit allocation algorithms in the literature.