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Approches théoriques en codage vidéo robuste multi-terminal.

Abstract : In this thesis, new robust video compression techniques are proposed for multi-terminal coding. We first compare four video multiple description coding schemes based on different time splitting patterns and temporal two- or three-band motion-compensated temporal filtering (MCTF). Then, the latter schemes are extended with systematic lossy description coding where the original sequence is separated into two sub-sequences, one being coded as in the latter schemes, and the other being coded with a Wyner-Ziv encoder. This amounts to having a systematic lossy Wyner-Ziv coding of every other frame of each description. This error control approach can be used as an alternative to Automatic Repeat Request (ARQ) or Forward Error Correction (FEC), i.e. the additional bitstream can be systematically sent to the decoder or can be requested, as in ARQ. When used as a FEC mechanism, the amount of redundancy is mostly controlled by the quantization of the Wyner-Ziv data. In this context, this approach leads to satisfactory rate-distortion performance at the side decoders, however suffers from high redundancy which penalizes the central description. To cope with this problem, the approach is then extended to the use of MCTF for the Wyner-Ziv frames, in which case only the low-frequency subbands are Wyner-Ziv encoded and sent in the descriptions. Next, we propose a multiple description coding scheme with side information at the receiver. It builds upon both multiple description coding principles and Slepian-Wolf coding principles. The input source is first quantized with a multiple description scalar quantizer (MDSQ) which introduces redundancy or correlation in the transmitted streams in order to take advantage of the path diversity. The resulting sequences of indexes are Slepian-Wolf encoded, that is separately encoded and jointly decoded. While the first step (MDSQ) plays the role of a channel code, the second one (Slepian-Wolf coding) plays the role of a source code, compressing the sequences of quantized indexes. In a second step, the cross-decoding of the two descriptions is proposed. This allows us to account for both the correlation with the side information as well as the correlation between the two descriptions. Then, we propose a way to improve the robustness of distributed video coding while keeping good rate-distortion performance by structuring the input sequence into groups of picture, each containing one key frame and one Wyner-Ziv frame. For each frame, two descriptions are generated by a MDSQ. This provides two balanced descriptions that contain partial information about every frame in the video input. At the central decoder, iterative decoding of the two Wyner-Ziv descriptions along with side information is performed. We study the influence of the cross-decoding and of the amount of redundancy on the performance.
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Submitted on : Friday, April 10, 2009 - 8:00:00 AM
Last modification on : Friday, July 31, 2020 - 10:44:05 AM
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  • HAL Id : pastel-00004774, version 1



Olivier Crave. Approches théoriques en codage vidéo robuste multi-terminal.. domain_other. Télécom ParisTech, 2008. English. ⟨pastel-00004774⟩



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