Lossy Packet Networks Research Articles

Diversity Image Coding Using Irregular Interpolation.

Diversity "multiple description" (MD) source coding promises graceful degradation in the presence of a priori unknown number of erased packets in the channel. A simple coding scheme for the case of two packets consists of oversampling the source by a factor of two and delta-sigma quantization. This approach was applied successfully to JPEG-based image coding over a lossy packet network, where the interpolation and splitting into two descriptions are done in the discrete cosine transform (DCT) domain. Moreover, unlike the classical source-channel separation approach - which is designed for a predetermined number of erasures (say, K out of N ), hence its distortion does not improve when the channel behaves better than expected - an MD coding scheme aims to achieve a better reconstruction quality when more or all the N descriptions are received at the decoder side. The extension to a larger number of descriptions, however, suffers from noise amplification whenever the received descriptions form a non-uniform sampling pattern. In this work, we examine inter- and intra-block interpolation methods, and show how noise amplification can be reduced by redesigning the interpolation filter at the encoder. Specifically, for a given total coding rate, we demonstrate that an "irregular" interpolation filter is robust to the pattern of received packets over all ( K out of N ) patterns, with some degradation relative to low-pass (LP) interpolation in the case where all N packets arrived. We provide experimental results comparing LP and irregular interpolation filters, and examine the effect of noise shaping on the trade-off between the central distortion (receiving all packets) and side distortion (receiving K packets).

In favor of fully intra coding for HEVC video transmission over lossy channels

Packet loss is inevitable when the video is transmitted over lossy channels. HEVC, due to the relatively large coding unit and high compression ratio, is much sensitive to data loss. Against the data loss, the responses of inter or intra coded blocks/frames are not the same. In the case of intra coding, the inter-frame dependency is removed and hence the error propagation is mitigated. However, with intra coding, since there is no motion vector, error concealment is more challenging than inter coding. Another difference between inter and intra coding is compression ratio where it is usually much better when using inter prediction. In this paper, taking into account the above trade-offs, a series of experiments is conducted to show the domain of preference of intra or inter coding in the application of HEVC video transmission over packet lossy networks. It is achieved that, if ratio of bitrates of I-Frames and P-Frames is smaller than a threshold, fully intra coding provides higher PSNR than some complicated methods; the improvement is as much as 2.5 dB sometimes. The performance of the proposed method is not the best as experimental results show, but besides its acceptable Rate-Quality behavior, it provides some side advantages.

Unequal Loss Protection Using Layer-Based Recovery Rate (ULP-LRR) for Robust Scalable Video Streaming over Wireless Networks

Scalable video streaming over wireless networks has many challenges. The most significant challenge is related to packet loss. To overcome this problem, in this paper, we propose an unequal loss protection (ULP) method using a new forward error correction (FEC) mechanism for robust scalable video streaming over wireless networks. For an efficient FEC assignment considering video quality, we first introduce a simple and efficient performance metric, the layer-based recovery rate (LRR), for quantifying the unequal error propagation effects of the temporal and quality layers on the basis of packet losses. LRR is based on the unequal importance in both the temporal and the quality layers of a hierarchical scalable video coding structure. Then, the proposed ULP-LRR method assigns an appropriate number of FEC packets on the basis of the LRR to protect the video layers against packet lossy network environments. Compared with conventional ULP algorithms, the proposed ULP-LRR algorithm demonstrates a higher performance for various error-prone wireless channel statuses.

Reliable scalable video streaming using layer weight switching‐based unequal Luby transform

A layer weight switching-based unequal Luby transform (LWS-ULT) method is proposed to minimise video distortion over packet-lossy networks. The proposed ULT method divides all quality layers into more important set (MIS) and less important set to provide unequal packet protection property in LT codes based on error propagation effects. The number of quality layer in MIS is adjusted in accordance with channel status. At high packet loss rate, lower number of quality layer is assigned into MIS for more protection of quality layer with larger error propagation weight. On the other hand, higher number of quality layer is included in MIS for improving video quality by expanding the range of protection at low packet loss rate. Simulation results demonstrate that the proposed LWS-ULT method gives robust performance and significantly improved video quality (0.9–1.2 dB in Y-PSNR), compared with the conventional ULT schemes.

Split-TCP based acceleration gateway over packet lossy networks

The conservative Additive Increase Multiplicative Decrease mechanism of traditional TCP causes the link under-utilization in the Wide Area Networks (WANs) due to the WANs' intrinsic nature of high latency and high packet loss. To alleviate the problem, we present the design and implantation of STAG, an Acceleration Gateway with Split-TCP in the paper. STAG is built on embedded network equipment and acts as a transparent proxy. In STAG, a new improved congestion control method named Rapid TCP is adopted, which determines whether or not to decrease the congestion window based on the packet loss trend. In particular, in the fast recovery phase, it chooses different window adjustment strategies based on the current size of congestion window to achieve higher utilization. The performance validation of STAG is done on both our emulation testbed and the real wide area network. The results show that STAG with Rapid TCP effectively adapts to the high loss network environment and significantly speeds up the applications without loss of fairness.

Multiple description video coding using correlation optimized temporal sampling

We propose a novel multiple description video coding scheme based on pre- and post-processing of video sequences without modifying the actual coding process itself, thus making it compatible with the current standard coding. In pre-processing, adaptive modes of temporal sampling are employed to regulate the motion change between frames before performing odd/even frame splitting, which facilitates good estimation of lost frames in post-processing after side decoding. Significantly, given a central distortion, rate-distortion optimization with Lagrangian formulation is applied in pre-processing to achieve a good tradeoff between bit rate and side distortion. Furthermore, to simplify Lagrangian optimization, a new optimization criterion is proposed based on the correlation of intra- and inter-descriptions. In the experiments, the proposed scheme achieves better performance compared with other tested multiple description coding (MDC) schemes in both an on-off MDC environment and lossy packet networks.

Unequal Loss Protection for H.264/AVC Video Streaming Over Wireless Networks

An efficient unequal loss protection (ULP) scheme for robust delivery of pre-encoded video with data partitioning over packet-lossy wireless networks is presented. The proposed scheme employs forward error correction (FEC) across packets to cope with the unreliable situations of the channel. To optimally allocate FEC codes for the different partitions packets of the different frames in one group of pictures (GOP), the overall expected distortion over one GOP is developed as the performance metric to guide the optimization process. In addition, a low-complexity FEC allocation algorithm is also proposed. Experimental results demonstrate that, compared with the other loss protection schemes, the proposed scheme achieves better reconstructed video quality.

Practical distributed video coding in packet lossy channels

Improving error resilience of video communications over packet lossy channels is an important and tough task. We present a framework to optimize the quality of video communications based on distributed video coding (DVC) in practical packet lossy network scenarios. The peculiar characteristics of DVC indeed require a number of adaptations to take full advantage of its intrinsic robustness when dealing with data losses of typical real packet networks. This work proposes a new packetization scheme, an investigation of the best error-correcting codes to use in a noisy environment, a practical rate-allocation mechanism, which minimizes decoder feedback, and an improved side-information generation and reconstruction function. Performance comparisons are presented with respect to a conventional packet video communication using H.264/advanced video coding (AVC). Although currently the H.264/AVC rate-distortion performance in case of no loss is better than state-of-the-art DVC schemes, under practical packet lossy conditions, the proposed techniques provide better performance with respect to an H.264/AVC-based system, especially at high packet loss rates. Thus the error resilience of the proposed DVC scheme is superior to the one provided by H.264/AVC, especially in the case of transmission over packet lossy networks.

Adaptive multiple description video coding and transmission for scene change

In view of perfect compatibility with the standard source and channel codec, temporal sampling-based multiple description coding (MDC) has become a better choice for practical applications. However, for the frames change from one scene to another temporal correlation may be destroyed by temporal sampling extremely, which results in the false estimation when the related frames are lost at the side decoder. Therefore, in this article the frames containing scene change are detected and duplicated before temporal sampling, which maintains better temporal correlation in each description. Furthermore, for better rate distortion performance temporal sampling is employed adaptively, that is, frame skipping or up-sampling according to the motion characteristics in original video. The experimental results exhibit better performance of the proposed scheme than other schemes whether in the on–off MDC environment or packet lossy network, especially about 15 dB improvements for the frames with scene change. Therefore, it may be a promising choice for video transmission over error-prone channels, especially over wireless networks.

A cost-effective cloud computing framework for accelerating multimedia communication simulations

Multimedia communication research and development often requires computationally intensive simulations in order to develop and investigate the performance of new optimization algorithms. Depending on the simulations, they may require even a few days to test an adequate set of conditions due to the complexity of the algorithms. The traditional approach to speed up this type of relatively small simulations, which require several develop–simulate–reconfigure cycles, is indeed to run them in parallel on a few computers and leaving them idle when developing the technique for the next simulation cycle. This work proposes a new cost-effective framework based on cloud computing for accelerating the development process, in which resources are obtained on demand and paid only for their actual usage. Issues are addressed both analytically and practically running actual test cases, i.e., simulations of video communications on a packet lossy network, using a commercial cloud computing service. A software framework has also been developed to simplify the management of the virtual machines in the cloud. Results show that it is economically convenient to use the considered cloud computing service, especially in terms of reduced development time and costs, with respect to a solution using dedicated computers, when the development time is longer than one hour. If more development time is needed between simulations, the economic advantage progressively reduces as the computational complexity of the simulation increases.

Joint Redundant and Random Network Coding for Robust Video Transmission over Lossy Networks

In this paper a novel unequal packet loss protection scheme R2NC based on low-triangular global coding matrix with ladder-shaped partition is presented, which combines redundant and random network coding for robust H.264/SVC video transmission. Firstly, the error-correcting capabilities of redundant network coding make our scheme resilient to loss. Secondly, the implementation of random network coding at the intermediate nodes with multiple input links can reduce the cost of network bandwidth, thus reducing the end-to-end delay for video transmission. Thirdly, the low-triangular global coding matrix with ladder-shaped partition is maintained throughout the R2NC processes to reduce the impact of global coding matrix's rank deficiency on video transmission and provide unequal erasure protection for H.264/SVC priority layers. The redundant network coding avoids the retransmission of lost packets and improves error-correcting capabilities of lost packets. Based only on the knowledge of the packet loss rates on the output links, the source node and intermediate nodes can make decisions for redundant network coding and random network coding (i.e., how much redundancy to add at this node). However, the redundancy caused by redundant network coding makes the network load increases. In order to improve network throughput, we performed random network coding at the intermediate nodes. Our approach is grounded on the overall distortion of reconstructed video minimization by optimizing the amount of redundancy assigned to each layer. The convex optimization model is constructed under the constraint of network coding and scalable video coding. Experimental results are shown to demonstrate the significant improvement of H.264/SVC video reconstruction quality with R2NC over packet lossy networks.

ContentAdaptive Refined Error Concealment Schemes for H.264/AVC Video Coding

this paper, we propose content-adaptive refined error concealment schemes for video transmission over packet lossy networks. The proposed spatial and temporal error concealment algorithms improve the reconstructed video quality at the common loss rates encountered on the networks. To reduce the computational complexity, the proposed schemes make use of the existing information of Intra prediction modes from the coded bit-stream for spatial error concealment. Neighboring macroblocks mode information is used to adapt the partition size of the lost macroblock to enhance the temporal error concealment performance. In addition, overlapped motion compensation is used to avoid the spatial discontinuities. A hybrid spatio-temporal concealment scheme is also proposed to use the appropriate algorithm for the lost macroblocks in the Inter frames. Experimental results demonstrate that the proposed schemes improve the concealment performance and reduce the structural degradations.

Unequal Error Protection Using Fountain Codes With Applications to Video Communication

Application-layer forward error correction (FEC) is used in many multimedia communication systems to address the problem of packet loss in lossy packet networks. One powerful form of application-layer FEC is unequal error protection which protects the information symbols according to their importance. We propose a method for unequal error protection with a Fountain code. When the information symbols were partitioned into two protection classes (most important and least important), our method required a smaller transmission bit budget to achieve low bit error rates compared to the two state-of-the-art techniques. We also compared our method to the two state-of-the-art techniques for video unicast and multicast over a lossy network. Simulations for the scalable video coding (SVC) extension of the H.264/AVC standard showed that our method required a smaller transmission bit budget to achieve high-quality video.

MMSE-Based Packet Loss Concealment for CELP-Coded Speech Recognition

In this paper, we analyze the performance of network speech recognition (NSR) over IP networks, adapting and proposing new solutions to the packet loss problem for code excited linear prediction (CELP) codecs. NSR has a client-server architecture which places the recognizer at the server side using a standard speech codec for speech transmission. Its main advantage is that no changes are required for the existing client devices and networks. However, the use of speech codecs degrades its performance, mainly in the presence of packet losses. First, we study the degradations introduced by CELP codecs in lossy packet networks. Later, we propose a reconstruction technique based on minimum mean square error (MMSE) estimation using hidden Markov models. This approach also allows us to obtain reliability measures associated to each estimate. We show how to use this information to improve the recognition performance by means of soft-data decoding and weighted Viterbi algorithm. The experimental results are obtained for two well-known CELP codecs, G.729 and AMR 12.2 kbps, carrying out recognition from decoded speech. Finally, we analyze an efficient and improved implementation of the proposed techniques using an NSR system which extracts speech recognition features directly from the bit-stream parameters. The experimental results show that the different proposed NSR systems achieve a comparable performance to distributed speech recognition (DSR).

Image and video transmission: a comparison study of using unequal loss protection and multiple description coding

We present a performance comparison between multiple description coding (MDC) and unequal loss protection (ULP) as tools to deliver multimedia data to mobile users. Graceful-degradation encoding schemes are able to cope with packet losses due to time-variant channels as they allow the receivers to partially reconstruct the transmitted data with only a subset of received packets. We address a rate-distortion-based multiple description coding scheme and a state-of-the-art unequal loss protection algorithm based on Reed Solomon Forward Error Correction (FEC) codes. The comparison is performed using as a case study JPEG 2000 coded images and H.264/AVC video sequences transmitted over lossy packet networks. Complexity aspects are also considered. The simulation results show that both schemes allocate the same amount of redundancy for any given encoding output rate to protect the transmitted information. The main findings are that MDC, besides being computationally less intensive, achieves a smoother performance degradation, whereas, the ULP scheme yields superior performance in terms of the expected PSNR.

Unequal Error Protection for Robust Streaming of Scalable Video Over Packet Lossy Networks

Efficient bit stream adaptation and resilience to packet losses are two critical requirements in scalable video coding for transmission over packet-lossy networks. Various scalable layers have highly distinct importance, measured by their contribution to the overall video quality. This distinction is especially more significant in the scalable H.264/advanced video coding (AVC) video, due to the employed prediction hierarchy and the drift propagation when quality refinements are missing. Therefore, efficient bit stream adaptation and unequal protection of these layers are of special interest in the scalable H.264/AVC video. This paper proposes an algorithm to accurately estimate the overall distortion of decoder reconstructed frames due to enhancement layer truncation, drift/error propagation, and error concealment in the scalable H.264/AVC video. The method recursively computes the total decoder expected distortion at the picture-level for each layer in the prediction hierarchy. This ensures low computational cost since it bypasses highly complex pixel-level motion compensation operations. Simulation results show an accurate distortion estimation at various channel loss rates. The estimate is further integrated into a cross-layer optimization framework for optimized bit extraction and content-aware channel rate allocation. Experimental results demonstrate that precise distortion estimation enables our proposed transmission system to achieve a significantly higher average video peak signal-to-noise ratio compared to a conventional content independent system.

A Comparison Between ULP and MDC With Many Descriptions for Image Transmission

In this letter, we present a performance comparison between multiple description coding (MDC) and unequal loss protection (ULP) for progressive image transmission over lossy packet networks. Two optimization criteria are considered, i.e., a multi-quality criterion, when N distinct quality levels are guaranteed at the decoder side, and the optimization of the expected quality at the receiver. We resort to both a semi-analytical approach and simulation results. To enable numerical comparisons, we address a specific MDC algorithm suitable for progressive imaging, and a state-of-the-art ULP algorithm based on Reed Solomon codes. The results, although cannot be generalized to any MDC and ULP methods, are useful to put into evidence some general features that can drive the selection of the most proper technique for the application at hand. In fact, they allow to put into evidence the main advantages and drawbacks of either technique.

Optimal Packet Loss Protection of Progressively Compressed 3-D Meshes

We consider a state-of-the-art system that uses layered source coding and forward error correction with Reed-Solomon codes to efficiently transmit 3-D meshes over lossy packet networks. Given a transmission bit budget, the performance of this system can be optimized by determining how many layers should be sent, how each layer should be packetized, and how many parity bits should be allocated to each layer such that the expected distortion at the receiver is minimum. The previous solution for this optimization problem uses exhaustive search, which is not feasible when the transmission bit budget is large. We propose instead an exact algorithm that solves this optimization problem in linear time and space. We illustrate the advantages of our approach by providing experimental results for the compressed progressive meshes (CPM) mesh compression technique.

Scalable Video Multicast Using Expanding Window Fountain Codes

Fountain codes were introduced as an efficient and universal forward error correction (FEC) solution for data multicast over lossy packet networks. They have recently been proposed for large scale multimedia content delivery in practical multimedia distribution systems. However, standard fountain codes, such as LT or Raptor codes, are not designed to meet unequal error protection (UEP) requirements typical in real-time scalable video multicast applications. In this paper, we propose recently introduced UEP expanding window fountain (EWF) codes as a flexible and efficient solution for real-time scalable video multicast. We demonstrate that the design flexibility and UEP performance make EWF codes ideally suited for this scenario, i.e., EWF codes offer a number of design parameters to be ldquotunedrdquo at the server side to meet the different reception criteria of heterogeneous receivers. The performance analysis using both analytical results and simulation experiments of H.264 scalable video coding (SVC) multicast to heterogeneous receiver classes confirms the flexibility and efficiency of the proposed EWF-based FEC solution.

Improved Resilience for Video Over Packet Loss Networks With MDC and Optimized Packetization

We investigate the problem of robust video transmission over lossy packet networks. A resilient video coding framework is important to ensure quality video over these networks. We propose a combination of a rate-distortion optimized multiple description codec and an integrated packetization method to constitute the error resilient codec. Multiple description (MD) coding techniques utilize path-diversity (multiple paths between sender and receiver) in networks by sending the descriptions along different paths. Two different optimization controls for the MD codec are proposed that are suited to variable rates of packet loss for multipath transmission of the MD coded video. An optimized strategy for packetizing the descriptions is also proposed which guarantees that each packet is self-contained and efficient. Simulations done under various packet loss scenarios show the need for two different optimization strategies and also that the developed MD codec achieves significantly improved video quality when compared with similar techniques.