Emerging IPTV technology uses source-specific IP multicast to deliver television programs to end-users. To
provide reliable IPTV services over the error-prone DSL access networks, a combination of multicast forward
error correction (FEC) and unicast retransmissions is employed to mitigate the impulse noises in DSL links.
In existing systems, the retransmission function is provided by the Retransmission Servers sitting at the edge
of the core network. In this work, we propose an alternative distributed solution where the burden of packet
loss repair is partially shifted to the peer IP set-top boxes. Through Peer-Assisted Repair (PAR) protocol, we
demonstrate how the packet repairs can be delivered in a timely, reliable and decentralized manner using the
combination of server-peer coordination and redundancy of repairs. We also show that this distributed protocol
can be seamlessly integrated with an application-layer source-aware error protection mechanism called forward
and retransmitted Systematic Lossy Error Protection (SLEP/SLEPr). Simulations show that this joint PARSLEP/
SLEPr framework not only effectively mitigates the bottleneck experienced by the Retransmission Servers,
thus greatly enhancing the scalability of the system, but also efficiently improves the resistance to the impulse
We address the problem of rate allocation for video multicast over wireless mesh networks. An optimization
framework is established to incorporate the effects of heterogeneity in wireless link capacities, traffic contention
among neighboring links and different video distortion-rate (DR) characteristics. We present a distributed rate
allocation scheme with the goal of minimizing total video distortion of all peers without excessive network
utilization. The scheme relies on cross-layer information exchange between the MAC and application layers. It
adopts the scalable video coding (SVC) extensions of H.264/AVC for video rate adaptation, so that graceful
quality reduction can be achieved at intermediate nodes within each multicast tree. The performance of the
proposed scheme is compared with a heuristic scheme based on TCP-Friendly Rate Control (TFRC) for individual
peers. Network simulation results show that the proposed scheme tends to allocate higher rates for peers
experiencing higher link speeds, leading to higher overall video quality than the TFRC-based heuristic scheme.
Wireless ad hoc networks present a challenge for error-resilient video transmission, since node mobility and
multipath fading result in time-varying link qualities in terms of packet loss ratio and available bandwidth.
In this paper, we propose to use a systematic lossy error protection (SLEP) scheme for video transmission
over wireless ad hoc networks. The transmitted video signal has two parts - a systematic portion consisting of a video sequence transmitted without channel coding over an error-prone channel, and error protection information consisting of a bitstream generated by Wyner-Ziv encoding of the video sequence. Using an end-to-end video distortion model in conjunction with online estimates of packet loss ratio and available bandwidth, the optimal Wyner-Ziv description can be selected dynamically according to current channel conditions. The scheme can also be applied to choose one path for transmission from amongst multiple candidate routes with varying available bandwidths and packet loss ratios, so that the expected end-to-end video distortion is maximized. Experimental results of video transmission over a simulated ad hoc wireless network shows that the proposed SLEP scheme outperforms the conventional application layer FEC approach in that it provides graceful degradation of received video quality over a wider range of packet loss ratios and is less susceptible to inaccuracy in the packet loss ratio estimation.
We propose a novel approach that uses disparity-compensated
lifting for wavelet compression of light fields. Disparity
compensation is incorporated into the lifting structure for the
transform across the views to solve the irreversibility limitation
in previous wavelet coding schemes. With this approach, we obtain
the benefits of wavelet coding, such as scalability in all
dimensions, as well as superior compression performance. For light
fields of an object, shape adaptation is adopted to improve the
compression efficiency and visual quality of reconstructed images.
In this work we extend the scheme to handle light fields with
arbitrary camera arrangements. A view-sequencing algorithm is
developed to encode the images. Experimental results show that
the proposed scheme outperforms existing light field compression
techniques in terms of compression efficiency and visual quality
of the reconstructed views.