Encoding of images based on a lapped orthogonal transform
نویسندگان
چکیده
Unitary transform image coding bas been successfully applied to image data compression. However, traditional block transform image coding systems generate artifacts near block boundaries which degrade low bit rate coded images. To reduce these artifacts a new class of unitary transformations, defined here as lapped orthogonal transforms (LOT), has been investigated. The basis functions upon which the signal is projected are overlapped for adjacent blocks. An example of a LOT optimized in terms of energy compaction was numerically derived using an augmented Lagrangian optimization algorithm. Using this LOT, intraframe coding experiments for 256 x 240 pixel images were performed at bit rates between 0.1 and 0.35 bits/pixel. The LOT improved tbe coded image subjective quality over otber transforms such as the discrete cosine transform (DCT) and tbe short-space Fourier transform (SSFf). The LOT was also used in interframe full-motion video coding experiments for head and shoulder sequences at 28 and 56 kbits/s. Experiments designed to measure tbe subjective quality assessment showed that significant improvement resulted at low data rates and if no motion compensation were used. However, the improvement was no longer significant at 56 kbits/s with full motion compensation.
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عنوان ژورنال:
- IEEE Trans. Communications
دوره 37 شماره
صفحات -
تاریخ انتشار 1989