Oregon State University

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Event Details

PhD Oral Preliminary Examination – Mohammed Sinky

Thursday, June 7, 2012 9:00 AM - 11:00 AM

Adaptive Retransmission for H.264 High Definition Video Over 802.11 Networks
H.264/MPEG-4 Part 10 is the current defacto video codec and exhibits many improvements over its predecessors (MPEG-4, MPEG-2) in coding efficiency. Many platforms rang- ing from laptops to smartphones contain hardware accelerators dedicated to H.264. Furthermore, the codec is ideal for streaming High Definition (HD) video content over 802.11-based networks. However, the underlying IEEE 802.11 Medium Access Control (MAC) layer retransmits packets to ensure delivery. Packet retransmissions proceed until the default limit set by the standard (up to 6 retries), after which the packet is discarded. This built- in reliability mechanism can cause problems for streaming real- time compressed video. First, packets may exceed their playout deadlines, which are considered lost from the perspective of a decoder. Second, in the context of H.264 encoded video (Main Profile), the produced bitstream yields regions of varying impor- tance (reference frames vs predicted frames) within a Group of Pictures (GOP) that can give rise to error propagation following packet loss and delay. The MAC layer does not discriminate between packets in the assignment of the retry limit. In this paper we present an adaptive MAC layer retransmission scheme tailored to the H.264/AVC codec to improve video quality during periods of high contention on the wireless medium.

Major Advisor: Ben Lee
Committee: Huaping Liu
Committee: Bechir Hamdaoui
Committee: Roger Traylor
GCR: Keith Levien

Kelley Engineering Center (campus map)
Shannon Thompson
1 541 737 7234
shannon.thompson at oregonstate.edu
Sch Elect Engr/Comp Sci
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