Ce Zhu

An unequal packet loss resilience scheme for video over the Internet

We present an unequal packet loss resilience scheme for robust transmission of video over the Internet. By jointly exploiting the unequal importance existing in different levels of syntax hierarchy in video coding schemes, GOP-level and Resynchronization-packet-level Integrated Protection (GRIP) is designed for joint unequal loss protection (ULP) in these two levels using forward error correction (FEC) across packets. Two algorithms are developed to achieve efficient FEC assignment for the proposed GRIP framework: a model-based FEC assignment algorithm and a heuristic FEC assignment algorithm. The model-based FEC assignment algorithm is to achieve optimal allocation of FEC codes based on a simple but effective performance metric, namely distortion-weighted expected length of error propagation, which is adopted to quantify the temporal propagation effect of packet loss on video quality degradation. The heuristic FEC assignment algorithm aims at providing a much simpler yet effective FEC assignment with little computational complexity. The proposed GRIP together with any of the two developed FEC assignment algorithms demonstrates strong robustness against burst packet losses with adaptation to different channel status.

A unified architecture for real-time video-coding systems

This paper presents a unified architecture for a live video over the Internet with emphasis on solving some challenging problems such as network bandwidth adaptation for rate and congestion, loss packet recovery, joint source and channel coding, and packetization. In our architecture, a time-varying bit rate for the source coding and time-varying ratios for the channel coding are simultaneously computed by a new congestion-control protocol. An adaptive rate-control scheme is then proposed to calculate quantization parameters and to determine the number of skipping frames corresponding to the bit rate. An adaptive unequal error-control scheme is also provided to protect the bitstream. Furthermore, a simple and MPEG-4 standard compatible algorithm is designed to packetize generated bitstream at the SyncLayer by using the existing resynchronization marker approach. With the proposed architecture, the coding efficiency and the robustness of the whole system are improved greatly.

Degressive error protection algorithm for MPEG-4 FGS video streaming

This paper presents a novel degressive error protection (DEP) algorithm adaptive to time varying packet loss rate for robustly transporting MPEG-4 fine granularity scalability (FGS) bit-stream over the packet erasure networks. By exploiting the embedded nature of FGS enhancement-layer bit-stream, a rate-distortion (R-D) optimization framework is developed to optimally partition the FGS enhancement-layer bit-stream into blocks and then to apply DEP to blocks by forward error correction (FEC). Experimental results show that this algorithm achieves graceful degradation of video quality in a wide range of packet loss rates.

Unequal error protection for motion compensated video streaming over the Internet

This paper presents an unequal error protection scheme for motion compensated video over the Internet. The forward error correction (FEC) codes are optimally assigned to different frames in group of picture (GOP) by exploiting the temporal dependency among frames. To achieve optimal allocation of FEC assigned in GOP, we propose a performance criterion for the measurement of allocation, namely the expected length of error propagation (ELEP), which makes sense intuitively, as fewer frames corrupted implies better quality of reconstruction. Experiment results show the proposed scheme is robust to burst packet loss in the Internet. More importantly, graceful degradation of video quality is achieved by the proposed scheme as the packet loss probability of an Internet connection increases.

A novel joint rate control scheme for the coding of multiple real time video programs

The objective of joint rate control is to achieve a better and more uniform picture quality by exploiting the complexity of each program. In this paper, a novel joint rate control scheme is presented for real time coding of multiple video programs. In our scheme, the total available channel bandwidth is firstly assigned to each program in proportion to its information content. A novel control scheme, which is adaptive to the variation of distributed bandwidth, is then presented in our design to determine quantization parameters and the number of skipping frames for each program. As a result, the proposed scheme can be considered as a look current scheme, which outperforms many existing ones in terms of coding complexity and video quality.

Unequal packet loss resilience for MPEG-4 video over the Internet

In this paper, an unequal packet loss resilience scheme is proposed for robust transmission of MPEG-4 video over the Internet. By exploiting the unequal importance regularly distributed in different levels of MPEG-4 video coding hierarchy, a GOP- and resynchronization-packet-level integrated protection scheme (GRIP) is designed to integrate unequal loss protection (ULP) for these two levels together using forward error protection (FEC) across packets. Experimental results show that the proposed GRIP scheme has good performance against burst packet losses and can adapt to time-varying channel status fairly well.

A congestion control strategy for multipoint videoconferencing

We formulate a congestion control problem for multipoint videoconferencing by introducing the concept of generalized fairness. A numerical method is provided to solve such a congestion control problem. The proposed method is much simpler than an earlier proposed method. This is desirable because congestion control is executed in real time.

A router based unequal error control scheme for video over the Internet

This paper presents a router based unequal error protection scheme for video over the Internet. The proposed scheme classifies the whole bitstream into two priorities according to their importance and packetizes them into packets with two priorities. To reduce the loss ratio of video packets with higher priority, an active queue management scheme is designed at each router to provide more chance for these packets to transmit over the Internet. Compared to an end-to-end based approach, in which some redundancy packets are generated to protect the packets with higher priority, our proposed scheme utilizes the whole bandwidth for the source coding. Therefore, the final picture quality is improved.

An MPEG-4 FGS-based statistical multiplexer

We present a novel fine granular scalability (FGS)-based statistical multiplexing scheme for video broadcasting. In the light of our statistical study on intra- and inter-layer correlation, we develop a simple but efficient statistical multiplexing algorithm based on the proposed fairness criterion and smoothness constraint. Simulation results show effectiveness of the proposed statistical multiplexer in terms of high multiplexing efficiency, high bandwidth utilization, fairness and smoothness.