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Optimisation d'un schéma de codage d'image à base d'une TCD. Application à un codeur JPEG pour l'enregistrement numérique à bas débit

Abstract : In this thesis, we consider the optimization problem of a JPEG Coding/Decoding scheme and the reduction of blocking effects in transform image coding.
First we propose to optimize for minimum distortion the synthesis subband filters using the Wiener filters, then to calculate the optimal quantizer step sizes based on a rate-constrained image-adaptive quantization. A1 is the iterative algorithm that optimizes jointly the quantizer step sizes and the synthesis subband filters.
The blocking effects in transform image coding are assmilated block boundary discontinuities. These discontinuities represent the quantization error within a block that becomes high frequency quantization noises after reconstruction. To reduce the blocking artefacts we propose the algorithm B1 that minimizes the energy of high frequency quantization noises. A visual inspection of some reconstructed images after applying the algorithm B1 has allowed to evaluate the performance of such technique.
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Submitted on : Monday, April 5, 2004 - 5:57:37 PM
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  • HAL Id : tel-00005739, version 1

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Moussa Ammar. Optimisation d'un schéma de codage d'image à base d'une TCD. Application à un codeur JPEG pour l'enregistrement numérique à bas débit. Traitement du signal et de l'image [eess.SP]. Télécom ParisTech, 2002. Français. ⟨tel-00005739⟩

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