Abstract: Methods of encoding and decoding for video data are described in which multi-level significance maps are used in the encoding and decoding processes. The significant-coefficient flags that form the significance map are grouped into contiguous groups, and a significant-coefficient-group flag signifies for each group whether that group contains no non-zero significant-coefficient flags. A multi-level scan order may be used in which significant-coefficient flags are scanned group-by-group. The group scan order specifies the order in which the groups are processed, and the scan order specifies the order in which individual significant-coefficient flags within the group are processed. The bitstream may interleave the significant-coefficient-group flags and their corresponding significant-coefficient flags, if any.

Abstract: A method for assessing image quality between a reference image and an impaired image is disclosed. The method comprises the steps of subband decomposition of the luminance component of the reference image into N subbands, called reference subbands and of the luminance component of the impaired image into N subbands, called impaired subbands; errors computation from the reference subbands and from the impaired subbands; and pooling the computed the errors. The subband decomposition is based on a wavelet transform adapted to decompose each of the luminance components into L levels of decomposition, with L a positive integer determined as a function of the image height and of the distance of visualization.