Browsing by Author "Liao, Ru-Ling"

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Intra Line Copy for HEVC Screen Content Coding
(2014)
Chang, Tsui-Shan
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Chen, Chun-Chi
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Liao, Ru-Ling
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Kuo, Che-Wei
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Peng, Wen-Hsiao
This paper presents an intra line copy mode, which introduces a finer-granularity block partitioning structure for the intra copying technique, to further improve the coding efficiency for screen content. This mode first divides a prediction block horizontally or vertically into 1-pixel-wide lines and then operates intra copying line-by-line from the reconstructed pixels in the current frame. It shares some parallels with the notion of string matching widely used for lossless data compression. It, however, is more compliant to the current HEVC design and is parallel-friendly. This paper shall detail its various design issues, including the design of a fast algorithm based on hashing techniques and the impact of search window size on its performance and complexity trade-off Experimental results show that the proposed mode can offer 2.7-12.9% of BD-rate reductions, with 26% increase of encoding runtime while keeping the decoding runtime unchanged, when integrated into the SCM-1.0 test model.
On Comparison of Intra Line Copy and Intra String Copy for HEVC Screen Content Coding
(2015-01-01)
Liao, Ru-Ling
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Chen, Chun-Chi
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Peng, Wen-Hsiao
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資訊工程學系
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Department of Computer Science
Recently, Intra Line Copy (ILC) and Intra String Copy (ISC) have been introduced as effective means for screen content coding during the development of HEVC Screen Content Coding Extensions. Although conceptually sharing the same theoretical basis, which is essentially string matching, they differ from each other in a number of significant ways. This paper presents detailed comparisons between them with respect to their compression performance, runtime complexity and memory access bandwidth, in order to better understand their merits and faults. Experimental results indicate that they perform comparably to each other, with ILC generally performing better in coding mixed content and ISC better in coding pure screen content. When considering the impact on the memory access bandwidth and coding performance trade-offs, local search for ILC/ISC becomes more favorable than full-frame search in low-delay real-time applications.
SCREEN CONTENT CODING USING NON-SQUARE INTRA BLOCK COPY FOR HEVC
(2014-01-01)
Chen, Chun-Chi
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Xu, Xiaozhong
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Liao, Ru-Ling
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Peng, Wen-Hsiao
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Liu, Shan
To achieve high coding performance for screen content, the intra block copy (IntraBC) performs block matching within a limited area of the reconstructed samples inside the current picture. We further extend its notion from the unit of square coding unit (CU) to non-square prediction unit (PU) partitions. This design is then justified by theoretical and empirical analyses which reveal the same fact that blocks coded by IntraBC mode tend to enable more at smaller partition levels. Besides, the syntax design of the proposed method is fully aligned with that of inter partition modes. Therefore the architecture-wise change in video codec design can be minimized. The experimental results justify the effectiveness of the proposed mode for coding of screen content video. In particular, up to 19.5% rate reduction (with an average of 12.7%) relative to the HM-12.0+RExt-4.1 anchor can be achieved on top of the usage of CU-based IntraBC prediction.