Bidirectional block placement in corrupted fixed-length entropy coded video streams

Joint source-channel decoding of variable length codes (VLC) for image and video streaming transmission over unreliable links, such as wireless networks, is a subject of increasing interest. Much more residual source redundancy can be exploited when both types of correlation: (i) the correlation between bits inside a VLC codeword as well as; (ii) the correlation between VLC codewords of a VLC sequence unit (e.g. corresponding to one image block), are taken into account. The paper (Hang Nguyen et al, IEEE Int. Conf. on Acoustics, Speech, and Sigpro., 2004) proposes an optimum maximum likelihood (ML) decoder of VLC sequences which can exploit these two kinds of correlation and outperforms the existing VLC decoders. This paper proposes a reduced complexity version of this optimal VLC decoder. Simulation results show that the complexity is reduced by 5 in terms of number of possible candidates, while the performance is only slightly sub-optimal compared with the optimal version of the Hang Nguyen paper.

: The research tasks are: Task 1, Scalable Coding; Task 2, Alternatives to variable length coding (VLC); and Task3, Packetizing for Error Concealment. Initial work on Task 1 built on research from a prior DARPA contract, and resulted in a scalable video coder with the unique property of scalable transmission at six resolution/frame-rate combinations. Task 2 work combined fixed and variable length coding (VLC) into a joint coding approach with distinct robustness advantages, while giving up only a slight amount of performance versus straight VLC coding in the noise-free case. Task 3 Packetzing for Error Concealment explored the new technique dispersive packetization and combined it with error concealment in a state-of-the-art subband/wavelet image coder. An ns-2 network simulation revealed substantial robustness to packet loss error, with useable images recovered under packet loss rates at high as 30%, thus implementing the graceful degradation property.

This paper presents an MPEG-4 video codec, called MoVa, for video coding applications that adopts 3G-324M. We designed MoVa to be optimal by embedding a cost-effective ARM7TDMI core and partitioning it into hardwired blocks and firmware blocks to provide a reasonable tradeoff between computational requirements, power consumption, and programmability. Typical hardwired blocks are motion estimation and motion compensation, discrete cosine transform and quantization, and variable length coding and decoding, while intra refresh, rate control, error resilience, error concealment, etc. are implemented by software. MoVa has a pipeline structure and its operation is performed in four stages at encoding and in three stages at decoding. It meets the requirements of MPEG-4 SP@L2 and can perform either 30 frames/s (fps) of QCIF or SQCIF, or 7.5 fps (in codec mode) to 15 fps (in encode/decode mode) of CIF at a maximum clock rate of 27 MHz for 128 kbps or 144 kbps. MoVa can be applied to many video systems requiring a high bit rate and various video formats, such as videophone, videoconferencing, surveillance, news, and entertainment.

Multiple description coding (MD coding or MDC) generates multiple decodable bitstreams for a single source to combat packet loss, which is suitable for video streaming in error-prone wireless ad hoc networks. In this paper, two problems are investigated for MD coded video streaming in wireless ad hoc networks. The first problem addresses multipath selection for balanced two-description coded video streaming. We formulate an interference-aware MDC multipath routing for single-radio networks by employing a time-division link scheduling method to eliminate wireless interference, and ultimately obtain an optimal path selection corresponding to the minimum achievable distortion. A heuristic solution is developed for the interference-aware multipath routing, by defining a path metric taking into account interference, link bandwidth and link “up” probability. The second problem addresses MDC redundancy control according to varying channel conditions of multiple paths. We design an unbalanced redundant slice based two-description video coding, which optimally selects the amount of inserted redundancy for each description. Simulation results demonstrate the effectiveness of the proposed MDC multipath routing scheme and the unbalanced MD video coding approach over heterogeneous paths.KeywordsMultiple description video codingmultipath routingwireless ad hoc networkswireless interference

Entropy coders and 3D-Hadamard coefficients sequency scan order for a fast embedded color video codec

The convergence of Internet, multimedia and mobile applications has led to an increasing demand for efficient and reliable video data transmission over heterogeneous networks. Due to their coding efficiency, variable-length codes (VLC) are usually employed in the entropy coding stage of video compression standards. However, error propagation is a major problem associated with VLC. We propose the use of self-synchronizing VLC (SSVLC) to achieve the dual goal of optimal coding efficiency and optimal error localization. Performance evaluation has revealed that the use of SSVLC provides better performance than standard VLC techniques.

Many image and video compression algorithms work by splitting the image into blocks and producing variable-length code bits for each block data. If variable-length code data are transmitted consecutively over error-prone channel without any error protection technique, the receiving decoder cannot decode the stream properly. So the standard image and video compression algorithms insert some redundant information into the stream to provide some protection against channel errors. One of such redundancy is resynchronization marker, which enables the decoder to restart the decoding process from a known state in the event of transmission errors, but its frequent use should be restricted not to consume bandwidth too much. The Error Resilient Entropy Code (EREC) is well known method which can regain synchronization without any redundant information. It can work with the overall prefix codes, which many image compression methods use. This paper proposes an improvement to FEREC (Fast Error-Resilient Entropy Coding). It first calculates initial searching position according to bit lengths of consecutive blocks. Second, initial offset is decided using statistical distribution of long and short blocks, and initial offset is adjusted to insure all possible offset value can be examined. The proposed algorithm can speed up the construction of EREC slots, and can preserve compressed image quality in the event of transmission errors. The simulation result shows that the quality of transmitted image is enhanced about 0.3--3.5 dB compared with the existing FEREC when random channel error happens.

Noise characteristics of satellite communications favor source coding methods that do not use entropy or variable length coding. A 1-Kb associative memory (AM) has been developed to support the hardware for a more robust video data compression scheme, which combines the use of vector quantization (VQ) and differential pulse code modulation (DPCM). The AM has properties that can be used for a variety of other high-speed applications, such as nondestructive evaluation (NDE) and symbol synchronization. >

Video streaming over the internet for new 3D immersive media such as Virtual Reality and 360-degree videos has drawn great attention from both consumers and researchers in recent years. One of the biggest challenges in streaming such 3D media is the high bandwidth demands. While traditional 2D video streaming is still dominating network peak traffic, new inventions are accelerating the adoption of immersive contents and devices. A new Tile-based video is introduced in both a video codec and streaming layer to reduce the transferred media size. Dynamic adaptive streaming over HTTP has become one of the de facto effective adaptive streaming approaches that can fully utilize the existing physical IP network infrastructure. In this paper, we propose a tile-based streaming framework using software-defined networking. By prioritizing streaming flows, based on the region of interests, our approach can improve the user's quality of experience (QoE).

Efficient error protection strategies for robust satellite broadcast of high-definition television (HDTV) and conventional TV are investigated. The concatenated Reed-Solomon/convolutional code is preferred over the RS code for fewer adverse effects on variable-length codes. A decoded bit error rate of 10/sup -10/ or below can be achieved for all transmitted information at a low threshold E/sub b//N/sub 0/. The most critical video packet data are received near-error-free by using an additional layer of block coding with minimal redundancy and complexity. The effect of loss of synchronization for variable-length codewords due to channel errors is minimized by simple error detection and concealment methods. Digital transmission architectures for the satellite broadcast of HDTV and conventional TV are outlined. >

Video streaming over wireless ad-hoc networks requires appropriate routing and rate allocation mechanisms that efficiently adapt to the characteristics of such environments. The special features of ad-hoc networks also motivate us to introduce proper mechanisms in video coding, error concealment and various related areas. In this paper, we propose a framework for video streaming over wireless ad-hoc networks which utilizes the cooperation among network layers to perform the mentioned activities. We discuss the key parameters to be noticed in such a framework and explore several approaches in video streaming and rate allocation and select the suitable methods for our purpose. Focusing on the retransmission of lost video frames in response to ARQ requests, we try to minimize the delay between sending the ARQ request and receiving the lost frame, by selecting a route in which a node assists us in video streaming. Simulation results show the feasibility and the efficiency of the proposed framework.

With the rising penetration of smartphones in the consumer market, mobile multimedia content is becoming the dominant form of information that people produce and consume on a daily basis. In this paper we present a wireless multi-hop video streaming application for mobile phones with the Android operating system. This application allows to share live information captured by mobile phone sensors (e.g., camera, microphone) with persons that might be multiple wireless hops away. The video streaming is based on peer-to-peer communication between mobile phones, i.e. without the use of video processing servers or network infrastructure. We show the feasibility of such peer-to-peer video streaming application for Android phones in a variety of experiments that evaluate various video streaming scenarios, including various video codecs and various generations of Android phones.

In this paper, we characterize the achievable performance of a wavelet encoding-based videophone system, which further compresses and protects the wavelet-based video codec's bit-stream with the aid of reversible variable-length (RVLC) codes. More specifically, the video codec uses RVLC codes for compressing and protecting the video frame header. By contrast irregular convolutional codes (IRCCs) are used for unequal error protection of the video bitstream generated from the wavelet-subbands, when communicating over intersymbol interference (ISI) contaminated channels. At the receiver, the turbo-equalizer, the IRCC decoder and the RVLC decoder all employ the maximum a-posteriori (MAP) algorithm and their operations are performed in an iterative turbo-detection style. The proposed system was designed for maintaining a near-unimpaired video reconstruction quality for channel signal-to-noise ratios (SNR) in excess of about 5 dB, when communicating over a five-path dispersive AWGN channel.

Capturing or acquiring video data from advanced gadgets, like cell phone cameras, smart phones, camcorders, etc., is very recent and up growing trend. With the advancement of the video camera as the integrated part of these multimedia devices generates necessity for video stabilization. Digital video stabilization or video frame alignment techniques are used to improve quality of input video by removing the undesired camera motions jitters; undesirable jiggles etc. Many video stabilization techniques are developed till now but only fast and low computational complexity approaches can be applied on the embedded devices. The paper presents the review of fast block matching local motion vector estimation and alignment algorithm. Effectiveness of the algorithm is shown by quantitative evaluation. The proposed work will also help to boost the performance of various error concealment, error resilience and video quality improvement techniques in H.264/HEVC video codec.

Error concealment for robust arithmetic decoding in mobile radio environments