| Summary: | 碩士 === 國立交通大學 === 資訊科學與工程研究所 === 101 === The adaptive loop filter (ALF) is mainly used to reduce the quantization noise of reconstructed pictures, and provides, at the same time, a better quality of reference frames for coding future frames. In the High Efficiency Video Coding (HEVC), an optimal
filter is derived by minimizing the square error between original and reconstructed frames.
Such operation, however, needs an extra memory buffer to store the information, such as all the original and reconstructed pixels, of the current frame, and thus the encoding latency is inevitably risen up. To alleviate such problem, a so-called time-delay filter,
which is an optimal filter optimized for a previously coded frame, is applied as if it were found for the current frame. To keep the encoding at single block latency while retaining the
filters to be optimal for the current frame, this thesis studies the trade-offs between the coding performance and the encoding latency. A quadtree-like filter optimization algorithm is proposed to improve the coding performance at the cost of a higher rate overhead for
signaling filters. As compared with the HM-6.0 software, the proposed scheme achieves BD-rate saving of 0.3%. A negligible BD-rate loss of 0.3% is observed for the two-blocks encoding latency scheme. Although the two approaches do not bring any impact on the coding
performance in terms of BD-rate saving, they can still provide noticeable improvement to the visual quality of the reconstructed frames.
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