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This paper presents a DC coefficient estimation algorithm for intra-predicted residual blocks in the High-Efficiency Video Coding (HEVC) standard. Discarding the DC coefficient directly in each transform block leads to substantial bit-saving, but at the same time produces strong discontinuities between neighboring blocks. To overcome this problem, we propose an estimation algorithm for the DC coefficient, which solves an optimal offset in a closed-form to recover the corresponding block edges. Then, we embed this algorithm into HEVC in its rate-distortion optimized quantization and sign bit hiding steps. Furthermore, a flag is signaled to decide whether the DC estimation strategy is used for each transform block. Test results under the common test condition show that our algorithm achieves 1.5% and 1.6% BD-rate reduction on average for luma and chroma, respectively, under all intra configuration. In the meantime, our simulation results show that both encoding time and decoding time increase only slightly (about 10%, without any special optimization on programming our proposed algorithm). When testing the proposed DC estimation algorithm on inter coding configurations, including low delay with P pictures, low delay with B pictures, and random access, we can also achieve 0.5%-1.1% bit-rate savings on average, while nearly no extra encoding and decoding time is needed. © 1991-2012 IEEE.

This paper proposes a DC coefficient estimation algorithm for intra-predicted residual blocks in the High Efficiency Video Coding (HEVC) standard. Discarding the DC coefficient in the current coding block leads to a substantial bit-saving but produces at the same time strong discontinuities between this block and its neighboring reconstructed blocks. To overcome this problem, we propose an estimation algorithm for the DC coefficient, which solves an optimal offset in a closed form in the pixel domain to recover the corresponding block edges. Test results show that our algorithm achieves 1.0% and 1.4% BD-rate reduction on average for luma and chroma as compared with HM-16.6, respectively, when the sign-bit-hiding (SBH) technique is disabled. When SDH is set on, namely under the common test condition (CTC), the BD-rate reduction drops slightly to 0.7% and 1.1% for luma and chroma, respectively. In the meantime, the test results show that both encoding time and decoding time increase only slightly (about 10%, without any special optimization on programming our proposed algorithm).

This paper presents a new block-based coding method for HEVC intra coding. Pixels in each prediction block are divided into two parts: half pixels are coded by a smart padding technique together with a constrained quantization algorithm; whereas the other half are reconstructed by simple linear interpolations along the prediction direction utilizing the neighboring reference pixels and the first half coded pixels. In the implementation, we employ a competition mechanism between this new method and the original HEVC intra coding in order to choose the best mode for each prediction block. Simulation results show that about 2% BD-rate reduction has been achieved with respect to HEVC's intra coding.

This paper proposes a new adaptive sharpening filter based on guided image filter and improves HEVC's in-loop filter architecture by embedding sharpening filter between deblocking filter and SAO. The proposed algorithm classifies pixels of a frame into several groups according to uniform quantization of each pixel's Sum-Modified-Laplacian value and assigns identical optimal filtering parameters to the pixels belonging to the same group based on rate-distortion optimization. Simulation results show that our proposed algorithm achieves 0.7% on average and up to 8% BD-rate reduction with respect to the original HEVC in-loop filtering method. Encoding time increases slightly by about 15% and decoding time increases by 70% on average without special optimization of C++ program integrated in HM-16.5. © 2015 IEEE.

In this paper, we focus on the design of a new block-based image compression by using our proposed transform domain downward conversion (TDDC). Applied directly on each 16×16 macro-block of pixels, this downward conversion is implemented through our proposed advanced padding technique such that a non-zero 8×8 coefficient block (thus down-sized) is generated only at the top-left corner in the transform domain, accompanied by zeros in other 75% positions. Consequently, a considerable bit-count saving can be achieved for the whole macro-block. In the meantime, 25% pixels reserved during the TDDC may be directly reconstructed from the down-sized coefficient block while the other 75% pixels that are not reserved during the TDDC will be reconstructed via the interpolation. Finally, this TDDC-based compression is used in conjunction with the JPEG baseline coding method (i.e., 1-out-of-2 selection) according to a rate-distortion optimization (RDO) based criterion. Experimental results show that our proposed compression scheme provides a significant quality gain as compared with the original JPEG baseline coding method and another super-resolution directed down-sampling (SRDDS) based compression scheme.