Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494687
Title: Wavelet video compression for iterative wireless transceivers
Author: Pham, Anh Quang
ISNI:       0000 0001 3486 8914
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2008
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Abstract:
Over the last decades, there has been an increasing demand for multimedia services provided over both fixed and wireless channels. Designing robust image or video trans- mission systems for these multimedia services is hence of high importance. For the sake of exploring the feasibility of providing video services for mobile users, this thesis investigates the design of wireless video communication systems using the British Broadcasting Corporation's recent proprietary wavelet-based video codec referred to as the Dirac codec. More specifically, the Dirac video codec is capable of achieving an approximately two-fold bit rate reduction over MPEG-2 when compressing high definition video (e.g. 1920x1080 pixels), while achieving a high reconstructed video quality at a low bit-rate. The Dirac video-encoded bitstream is subjected to a rigorous error sensitivity investigation for the sake of assisting us in contriving various joint source-channel coding (JSCC) and decoding schemes for wireless videophones. Unequal Error Protection (UEP) is an attractive technique of implementing JSCC. Based on the Dirac video codec's bit sensitivity studies, an Unequal Error Protection (UEP) scheme using turbo-equalized Irregular Convolutional Codes (IRCCs) was de- signed. Our UEP scheme allocates a lower channel coding rate to highly sensitive bits and a higher channel coding rate to less sensitive bits, while keeping the coding-rate of the UEP the same as that of the Equal Error Protection (EEP) benchmarker. Furthermore, an Iterative Source-Channel Decoding (ISCD) scheme, which exploits the residual redundancy left in the source encoded bitstream for the sake of improving the attainable system performance was investigated. Hence, a novel ISCD scheme employing a specific bit-to-symbol mapping scheme referred to as Over-Complete Mapping (OCM) was proposed. The proposed scheme benefits both from the residual redundancy inherent in the source encoded bitstream as well as from the intentional redundancy imposed by the specific over-complete source mapping. This allows us to design an attractive video transmission scheme having a high error resilience at a reasonable complexity and a low delay. • The research reported in this thesis was concluded with the design of unequal error protection irregular over-complete mapping for wavelet video telephony using iterative source and channel decoding. The philosophy of this video telephone scheme is that we exploit as much redundancy inherent in the Dirac-encoded bitstream as possible for improving the system's BER performance, while protecting the more sensitive portions of the Dirac video-encoded sequence with a lower OCM rate. This design dilemma was addressed in the context of a novel Irregular Over-Complete Mapping (IrOCM) scheme constituted by the amalgam of appropriately weighted different-rate OCM schemes. Moreover, in order to accommodate the variations of the relative frequency of the K-bit source symbols used for modelling the Probability Density Function (PDF) of the different video-encoded bitstreams, a near-instantaneously adaptive transceiver for wireless video telephony was designed. This adaptive transceiver allows our wireless video telephone scheme to attain iterative detection gains without increasing the system's delay, regardless of the choice of the source codec - even for speech and audio codecs, and hence the novel OCM scheme is widely applicable.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.494687  DOI: Not available
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