Survey of Error Correction Mechanisms for Video Streaming over the Internet <s> VI. ERROR MECHANISMS: REVIEW <s> The problem of error control and concealment in video communication is becoming increasingly important because of the growing interest in video delivery over unreliable channels such as wireless networks and the Internet. This paper reviews the techniques that have been developed for error control and concealment. These techniques are described in three categories according to the roles that the encoder and decoder play in the underlying approaches. Forward error concealment includes methods that add redundancy at the source end to enhance error resilience of the coded bit streams. Error concealment by postprocessing refers to operations at the decoder to recover the damaged areas based on characteristics of image and video signals. Last, interactive error concealment covers techniques that are dependent on a dialogue between the source and destination. Both current research activities and practice in international standards are covered. <s> BIB001 </s> Survey of Error Correction Mechanisms for Video Streaming over the Internet <s> VI. ERROR MECHANISMS: REVIEW <s> Due to the explosive growth of the Internet and increasing demand for multimedia information on the Web, streaming video over the Internet has received tremendous attention from academia and industry. Transmission of real-time video typically has bandwidth, delay, and loss requirements. However, the current best-effort Internet does not offer any quality of service (QoS) guarantees to streaming video. Furthermore, for video multicast, it is difficult to achieve both efficiency and flexibility. Thus, Internet streaming video poses many challenges. In this article we cover six key areas of streaming video. Specifically, we cover video compression, application-layer QoS control, continuous media distribution services, streaming servers, media synchronization mechanisms, and protocols for streaming media. For each area, we address the particular issues and review major approaches and mechanisms. We also discuss the tradeoffs of the approaches and point out future research directions. <s> BIB002 </s> Survey of Error Correction Mechanisms for Video Streaming over the Internet <s> VI. ERROR MECHANISMS: REVIEW <s> Wireless video communication is particularly challenging because it combines the already difficult problem of efficient compression with the additional and usually contradictory need to make the compressed bit stream robust to channel errors. We describe design and implementation strategies for error-robust video communications with an emphasis on techniques compatible with the coding approaches used in the ISO (MPEG-4) and ITU standards organizations. These techniques include modifications to the video coding algorithms as well as to the system layers that perform packetization and multiplexing. <s> BIB003 </s> Survey of Error Correction Mechanisms for Video Streaming over the Internet <s> VI. ERROR MECHANISMS: REVIEW <s> Delivering real-time video over the Internet is an important component of many Internet multimedia applications. Transmission of real-time video has bandwidth, delay, and loss requirements. However the current Internet does not offer any quality of service (QoS) guarantees to video transmission over the Internet. In addition, the heterogeneity of the networks and end systems makes it difficult to multicast Internet video in an efficient and flexible way. Thus, designing protocols and mechanisms for Internet video transmission poses many challenges. In this paper, we take a holistic approach to these challenges and present solutions from both transport and compression perspectives. With the holistic approach, we design a framework for transporting real-time Internet video, which includes two components, namely, congestion control and error control. Specifically congestion control consists of rate control, rate-adaptive encoding, and rate shaping; error control consists of forward error correction (FEC), retransmission error resilience, and error concealment. For the design of each component in the framework, we classify approaches and summarize representative research work. We point out there exists a design space which can be explored by video application designers and suggest that the synergy of both transport and compression could provide good solutions. <s> BIB004 </s> Survey of Error Correction Mechanisms for Video Streaming over the Internet <s> VI. ERROR MECHANISMS: REVIEW <s> Real-time audio and video data streamed over unreliable IP networks, such as the Internet, may encounter losses due to dropped packets or late arrivals. This paper reviews error-concealment schemes developed for streaming real-time audio and video data over the Internet. Based on their interactions with (video or audio) source coders, we classify existing techniques into source coder-independent schemes that treat underlying source coders as black boxes, and source coder-dependent schemes that exploit coder-specific characteristics to perform reconstruction. Last, we identify possible future research directions. <s> BIB005 </s> Survey of Error Correction Mechanisms for Video Streaming over the Internet <s> VI. ERROR MECHANISMS: REVIEW <s> We review error resilience techniques for real-time video transport over unreliable networks. Topics covered include an introduction to today's protocol and network environments and their characteristics, encoder error resilience tools, decoder error concealment techniques, as well as techniques that require cooperation between encoder, decoder, and the network. We provide a review of general principles of these techniques as well as specific implementations adopted by the H.263 and MPEG-4 video coding standards. The majority of the article is devoted to the techniques developed for block-based hybrid coders using motion-compensated prediction and transform coding. A separate section covers error resilience techniques for shape coding in MPEG-4. <s> BIB006 </s> Survey of Error Correction Mechanisms for Video Streaming over the Internet <s> VI. ERROR MECHANISMS: REVIEW <s> We describe an effective method for increasing error resilience of video transmission over bit error prone networks. Rate-distortion optimized mode selection and synchronization marker insertion algorithms are introduced. The resulting video communication system takes into account the channel condition and the error concealment method used by the decoder, to optimize video coding mode selection and placement of synchronization markers in the compressed bit stream. The effects of mismatch between the parameters used by the encoder and the parameters associated with the actual channel condition and the decoder error concealment method are evaluated. Results for the binary symmetric channel and wideband code division multiple access mobile network models are presented in order to illustrate the advantages of the proposed method. <s> BIB007 </s> Survey of Error Correction Mechanisms for Video Streaming over the Internet <s> VI. ERROR MECHANISMS: REVIEW <s> Rate-distortion (R-D) optimized mode selection is a fundamental problem for video communication over packet-switched networks. The classical R-D optimized mode selection only considers quantization distortion at the source. Such an approach is unable to achieve global optimality under the error-prone environment since it does not consider the packetization behavior at the source, the transport path characteristics, and receiver behavior. This paper presents an end-to-end approach to generalize the classical theory of R-D optimized mode selection for point-to-point video communication. We introduce a notion of global distortion by taking into consideration both the path characteristics (i.e., packet loss) and the receiver behavior (i.e., the error concealment scheme), in addition to the source behavior (i.e., quantization distortion and packetization). We derive, for the first time, a set of accurate global distortion metrics for any packetization scheme. Equipped with the global distortion metrics, we design an R-D optimized mode selection algorithm to provide the best tradeoff between compression efficiency and error resilience. The theory developed in this paper is general and is applicable to many video coding standards, including H.261/263 and MPEG-1/2/4. As an application, we integrate our theory with point-to-point MPEG-4 video conferencing over the Internet, where a feedback mechanism is employed to convey the path characteristics (estimated at the receiver) and receiver behavior (error concealment scheme) to the source. Simulation results are discussed. <s> BIB008 </s> Survey of Error Correction Mechanisms for Video Streaming over the Internet <s> VI. ERROR MECHANISMS: REVIEW <s> Resilience to packet loss is a critical requirement in predictive video coding for transmission over packet-switched networks, since the prediction loop propagates errors and causes substantial degradation in video quality. This work proposes an algorithm to optimally estimate the overall distortion of decoder frame reconstruction due to quantization, error propagation, and error concealment. The method recursively computes the total decoder distortion at pixel level precision to accurately account for spatial and temporal error propagation. The accuracy of the estimate is demonstrated via simulation results. The estimate is integrated into a rate-distortion (RD)-based framework for optimal switching between intra-coding and inter-coding modes per macroblock. The cost in computational complexity is modest. The framework is further extended to optimally exploit feedback/acknowledgment information from the receiver/network. Simulation results both with and without a feedback channel demonstrate that precise distortion estimation enables the coder to achieve substantial and consistent gains in PSNR over known state-of-the-art RD- and non-RD-based mode switching methods. <s> BIB009 </s> Survey of Error Correction Mechanisms for Video Streaming over the Internet <s> VI. ERROR MECHANISMS: REVIEW <s> Applications where packetized video is streamed over the Internet, must be designed to achieve robustness to packet loss as well as compression efficiency. Whenever possible, the ideal solution to this problem is to jointly optimize the adaptation of the compression and error protection strategies to the network status, so as to minimize the expected end-to-end distortion of reconstructed video at the receiver. However, in the case of pre-compressed video streaming, compression is performed without knowledge of the network condition, and conversely the delivery is performed without access to the original signal. It is hence difficult for the transmitter to estimate and minimize the end-to-end distortion during delivery. This paper addresses this problem by deriving an algorithm which enables the transmitter, or other intermediate nodes, to estimate the overall end-to-end distortion while delivering pre-compressed video. This estimate fully accounts for the effects of (prior) quantization, packet loss and error propagation, as well as error concealment. The accuracy of the estimate is demonstrated by simulation results. The algorithm requires storage of minimal side-information that is computed during compression. The algorithm is of low complexity, and is applicable to virtually all coding techniques, including the standard (predictive) video coders. The paper also discusses the use of this estimate to adapt a variety of packet-loss resilience techniques for pre-compressed video streaming. The considerable potential gains of this approach are illustrated via the example of an FEC-based streaming video system. <s> BIB010 </s> Survey of Error Correction Mechanisms for Video Streaming over the Internet <s> VI. ERROR MECHANISMS: REVIEW <s> We present an effective framework for increasing the error-resilience of low bit-rate video communications over an error-prone packet-switched network. Our framework is based on the principle of layered coding with transport prioritization. We introduce a rate-distortion optimized mode-selection algorithm for our prioritized layered framework. This algorithm is based on a joint source/channel-coding approach and trades off source coding efficiency for increased bitstream error-resilience to optimize the video coding mode selection within and across layers. The algorithm considers the channel conditions, as well as the error recovery and concealment capabilities, of the channel codec and source decoder, respectively. Important framework parameters including the packetization scheme, decoder error concealment method, and channel codec error-protection strength are considered. The effects of mismatch between the parameters employed by the encoder and the actual channel conditions are considered. Results are presented for a wide range of packet loss rates in order to illustrate the benefits of the proposed framework. <s> BIB011
The current Internet Architecture does not meet with the needs of new applications like video streaming, which require high data throughput (bandwidth) and have low-latency requirements, current Internet transmits all packets with equal importance However. Video streaming over Internet is requiring number of requirements, such as minimum bandwidth, delay and loss. When we transported video over Internet, we have to take the congestion and error control in our consideration. This survey aims to introduce the error control mechanisms that are used to protect the data from errors caused by packet loss due to congestion and link failure. Since the packet loss is inevitable in the Internet BIB004 BIB002 several Error control mechanisms have been proposed for video applications to reduce the packet loss. These mechanisms can be classified into four types: forward error correction (FEC), retransmission, error resilience, and error concealment as shown in table 1. The basic idea of FEC BIB004 BIB001 is to use the channel coding or joint source/channel coding to add redundancy packets on compressed source packet to enable error detection and correction. Redundant packets are transmitted so that the original message can be reconstructed in case the packets are lost. If there are K data packets, FEC will add N -K redundant packets and the FEC overhead is N/K. Many researchers have been done in applying FEC packet, which is almost achieved by erasure codes BIB010 BIB011 , the most common erasure codes are RS (Reed-Solomon). Other erasure codes have been considered is Tornado code  . Retransmission BIB004 mechanisms based on the receiver notifies the sender which packets were received or lost and the sender have to resend lost packets. Retransmission requires back channel; hence it is easy to adapt changing channel conditions, but make it unsuitable to broadcast. Retransmission requires large transmission delay, so retransmission error controls mechanism unsuitable to be realtime application. Error Concealment BIB001 BIB005 is Receiver-based error, which means this method attempts to recover the lost information by estimation and interpolation without relying on additional information from the encoder. Error concealment offers a feasible technique for coping with packet loss from the compression perspective. Error concealment has two approaches, spatial and temporal interpolation. Error-resilient BIB003 , BIB006 schemes deal with packet loss on the compression layer like the error concealment. These schemes try to prevent error propagation or limit the scope of the damage caused by packet losses on the compression layer by adding redundancy data at the source coding, this technique is composed of resynchronization marking, data partitioning and data recovery. Many study have been done the error resilient source coding problem by using the optimal mode selection with (R-D) BIB007 BIB008 .Error-resilient BIB003 , BIB006 schemes deal with packet loss on the compression layer like the error concealment. These schemes try to prevent error propagation or limit the scope of the damage caused by packet losses on the compression layer by adding redundancy data at the source coding, this technique is composed of resynchronization marking, data partitioning and data recovery. Many study have done the error resilient source coding problem by using the optimal mode selection with (R-D) BIB007 BIB008 . There are three factors effect in the video quality BIB004 fig.  7 .show these factors. To achieve good performance of video streaming it is necessary to take into consideration the path characteristics, receiver behavior and source behavior BIB004 BIB009 . In this paper, we have described the error control mechanisms for video application, which can reduce the packet loss in order to provide good video quality. Existing error control mechanisms can be classified into four types, namely, forward error correction (FEC), retransmission, error resilience, and error concealment. The FEC is to add redundant bits on compressed source bits to enable error detection and correction. Advantage of FEC is its small transmission delay, but the FEC is ineffective if there are more than N-K consecutive packets lost. FEC schemes can be classified into three categories: a) Channel coding, b) Source coding-based FEC; and c) joint source/channel coding. In the retransmission the receiver notifies the sender which packets were received / lost and the sender re-sends lost packets. Retransmission includes delay-constrained retransmission so it is ineffective for interactive real-time video applications. Error-resilient coding schemes are developed to mitigate the effect of packet losses or to prevent error propagation from compression perspective. The errorresilient composed of resynchronization marking, data partitioning and data recovery. Error resilient source coding may use the optimal mode selection for each packet or multiple description coding (MDC). Error concealment is a post-processing technique executed only by decoders / receivers. The error concealment mechanism performs some forms of Spatial / temporal interpolation to estimate the lost information from the correctly received data. Any researcher working in the error control mechanisms to provide good video quality has to concentrate in of the following factors source coding, receiver coding and channel (path) to achieve good performance.