362 research outputs found
Adaptive Quantization Matrices for HD and UHD Display Resolutions in Scalable HEVC
HEVC contains an option to enable custom quantization matrices, which are
designed based on the Human Visual System and a 2D Contrast Sensitivity
Function. Visual Display Units, capable of displaying video data at High
Definition and Ultra HD display resolutions, are frequently utilized on a
global scale. Video compression artifacts that are present due to high levels
of quantization, which are typically inconspicuous in low display resolution
environments, are clearly visible on HD and UHD video data and VDUs. The
default QM technique in HEVC does not take into account the video data
resolution, nor does it take into consideration the associated display
resolution of a VDU to determine the appropriate levels of quantization
required to reduce unwanted video compression artifacts. Based on this fact, we
propose a novel, adaptive quantization matrix technique for the HEVC standard,
including Scalable HEVC. Our technique, which is based on a refinement of the
current HVS-CSF QM approach in HEVC, takes into consideration the display
resolution of the target VDU for the purpose of minimizing video compression
artifacts. In SHVC SHM 9.0, and compared with anchors, the proposed technique
yields important quality and coding improvements for the Random Access
configuration, with a maximum of 56.5% luma BD-Rate reductions in the
enhancement layer. Furthermore, compared with the default QMs and the Sony QMs,
our method yields encoding time reductions of 0.75% and 1.19%, respectively.Comment: Data Compression Conference 201
A two-stage video coding framework with both self-adaptive redundant dictionary and adaptively orthonormalized DCT basis
In this work, we propose a two-stage video coding framework, as an extension
of our previous one-stage framework in [1]. The two-stage frameworks consists
two different dictionaries. Specifically, the first stage directly finds the
sparse representation of a block with a self-adaptive dictionary consisting of
all possible inter-prediction candidates by solving an L0-norm minimization
problem using an improved orthogonal matching pursuit with embedded
orthonormalization (eOMP) algorithm, and the second stage codes the residual
using DCT dictionary adaptively orthonormalized to the subspace spanned by the
first stage atoms. The transition of the first stage and the second stage is
determined based on both stages' quantization stepsizes and a threshold. We
further propose a complete context adaptive entropy coder to efficiently code
the locations and the coefficients of chosen first stage atoms. Simulation
results show that the proposed coder significantly improves the RD performance
over our previous one-stage coder. More importantly, the two-stage coder, using
a fixed block size and inter-prediction only, outperforms the H.264 coder
(x264) and is competitive with the HEVC reference coder (HM) over a large rate
range
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