Lossy Error Protection Research Articles

IPTV Multicast With Peer-Assisted Lossy Error Control

Internet protocol television (IPTV) systems employ IP multicast to deliver television programs to end-users. To provide reliable IPTV services over the error-prone digital subscriber line (DSL) access networks, a combination of multicast forward error correction and unicast retransmissions is employed to mitigate the impulse noise in DSL links. In current systems, the error control function is provided by special retransmission servers. In this paper, we propose an alternative distributed solution where the burden of packet loss repair is partially shifted to end-user set-top boxes. Using a peer-assisted repair (PAR) protocol, we demonstrate how packet repairs can be delivered in a timely, reliable, and decentralized manner using the combination of server-peer coordination and redundant 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). Analysis and simulations show that this joint PAR-SLEP/SLEPr framework not only efficiently improves the resistance to the impulse noise but also effectively mitigates the bottleneck experienced by the retransmission servers, thus greatly enhancing system scalability.

Corrections to “Systematic Lossy Error Protection of Video Signals” [Oct 08 1347-1360

In the above titled paper (ibid., vol. 18, no. 10, pp. 1347-1360, Oct 08), Fig. 4 was printed incorrectly. The correct figure is presented here.

An Adaptive Systematic Lossy Error Protection Scheme for Broadcast Applications Based on Frequency Filtering and Unequal Picture Protection

Systematic lossy error protection (SLEP) is a robust error resilient mechanism based on principles of Wyner-Ziv (WZ) coding for video transmission over error-prone networks. In an SLEP scheme, the video bitstream is separated into two parts: a systematic part consisting of a video sequence transmitted without channel coding, and additional information consisting of a WZ supplementary stream. This paper presents an adaptive SLEP scheme in which the WZ stream is obtained by frequency filtering in the transform domain. Additionally, error resilience varies adaptively depending on the characteristics of compressed video. We show that the proposed SLEP architecture achieves graceful degradation of reconstructed video quality in the presence of increasing transmission errors. Moreover, it provides good performances in terms of error protection as well as reconstructed video quality if compared to solutions based on coarser quantization, while offering an interesting embedded scheme to apply digital video format conversion.

Systematic Lossy Error Protection of Video Signals

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper proposes a scheme called Systematic Lossy Error Protection (SLEP) for robust transmission of video signals over packet erasure channels. The systematic portion of the transmission consists of a conventionally encoded video bit stream which is transmitted without channel coding. An additional bit stream generated by Wyner–Ziv encoding of the video signal is transmitted for error resilience. In the event of packet loss, this supplementary bit stream is decoded and allows the recovery of a coarsely quantized video signal, which is displayed in lieu of the lost portions of the primary video signal. The quantization mismatch results in a small, controlled loss in picture quality, but a drastic reduction in picture quality is avoided. An implementation of the SLEP system using the state-of-the-art H.264/AVC standard codec is described. Specifically, H.264/AVC redundant slices are used in conjunction with Reed–Solomon coding to generate the Wyner–Ziv bit stream. The received video quality is modeled as a function of the bit rates of the primary and redundant descriptions and the error resilience bit rate. The model is used to optimize the video quality delivered by SLEP. Via theoretical analysis and experimental simulation, it is shown that SLEP provides a flexible tradeoff between error resilience and decoded picture quality. By allowing the quality to degrade gracefully over a wider range of packet loss rates, SLEP mitigates the precipitous drop in picture quality suffered by traditional FEC-based systems. </para>

Systematic Lossy Error Protection based on H.264/AVC redundant slices and flexible macroblock ordering

The authors propose a scheme for Systematic Lossy Error Protection (SLEP) of an H.264/AVC compressed video bit stream, using standard compatible features such as redundant slices, and flexible macroblock ordering. The systematic portion consists of a conventional H.264/AVC bit stream. For error resilience, an additional Wyner-Ziv bit stream is also transmitted. The Wyner-Ziv bit stream allows the decoding of a coarsely quantized description of the original video signal, and is efficiently gen- erated by using H.264/AVC redundant slices in conjunction with Reed-Solomon coding. The Wyner-Ziv bit stream is decoded in order to recover the redundant video descriptions, which are used in lieu of portions lost from the original video signal due to channel errors. SLEP allows the video quality to degrade gracefully with worsening channel conditions, and provides a flexible trade-off between the achieved error resilience and the coarseness of the redundant description. The performance can be improved especially for low motion video sequences, by applying SLEP to a region-of-interest in the video frame, using flexible macroblock ordering (FMO). Experimental results provided for two video transmission scenarios, demonstrate the advantages of SLEP over forward error correction (FEC) as an error resilience scheme.