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Reference : UMR8520-FRELEF-086
Workplace : VALENCIENNES
Date of publication : Tuesday, March 30, 2021
Scientific Responsible name : Patrick CORLAY - François Xavier COUDOUX
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 June 2021
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
The aim of this research is to study and optimize an extrapolation-based ZL hybrid video scheme benefiting from the best of both conventional and LVC worlds. An operational hybrid architecture will be developed, and a joint approach for finding the right balance between latency, bandwidth, and picture quality will be carried out for targeted use cases with different delay constraints.
To achieve both the efficiency of digital coding systems and the graceful degradation obtained by the LVC systems (even in the case of severe channels), hybrid ZL schemes will be considered. In these systems, the critical low frequency frame content (base layer) is encoded with a conventional coder (e.g. HEVC) and the residual frame is sent with LVC (enhancement layer). Both layers use the same extrapolation horizon to define the latency. Since time duplexing is prohibited in order to preserve latency, an OFDM transmission is considered where the signals of the two layers share the available bandwidth in a frequency multiplex or are superimposed in a hierarchical modulation scheme. In the latter case, the transmitted signal is the superposition of the reliably protected and digitally coded (BPSK/QPSK) base layer and the analog signal of the LVC enhancement layer. Quality and throughput are classically the antagonistic variables in the search for the best coding compromise, and in ZL-LVC, it is necessary to add the latency. In the context of transmission through wireless channels, the adaptive optimization of end-to-end video quality as well as the search for the optimal allocation of resources between the digital and analog parts will be studied. By considering the transmission channel, the optimization process may consider the well-protected error-free transmission of the base train, possibly with non-penalizing flat energy distribution over the entire used transmission band and rate-distortion (empirical) models in the literature.
Finally, hybrid schemes have recently gained interest also at MPEG standardization. The future MPEG-5 LC-EVC (a standardised and updated version of the proprietary V-NOVA Perseus video codec), has a low complexity enhancement layer added to a classic video base layer (AVC or HEVC), showing good coding efficiency. We intend to propose results within the MPEG-5 framework, in particular by using LVC as the enhancement layer.
The candidate will carry out his/her research in the Digital Communications group (COMNUM) of the Opto-Acousto-Electronics department (DOAE) of the Institute of Electronics, Microelectronics and Nanotechnology (IEMN UMR-CNRS 8520). The position is located on the Mont Houy campus of the Université Polytechnique Hauts-de-France (UPHF), in Valenciennes. The candidate will be part of a team of 5 researchers working on wireless communications, digital video transmission, joint source-channel-protocol coding, and artificial intelligence for video broadcast applications. The thesis topic is entitled: "Hybrid schemes for latency-free video transmission". The candidate will contribute to the design of a hybrid latency-free video scheme efficiently combining classical video compression techniques (HEVC, VVC, EVC) with linear video coding techniques (CVL).
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