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This article makes several improvements to the classic PPM algorithm, resulting in a new algorithm with superior compression effectiveness on human text. The key differences of our algorithm to classic PPM are that (A) rather than the original escape mechanism, we use a generalised blending method with explicit hyper-parameters that control the way symbol counts are combined to form predictions, (B)...
This paper presents an in-loop adaptive color-space transform for the HEVC Screen Content Coding extension. In the proposed method, the prediction residual is adaptively converted into a different color space to reduce the cross-component redundancy. After the ACT, the signal is coded following the existing HEVC framework. To keep the complexity as low as possible, fixed color-space transforms that...
Yahoo mail servers have been receiving an enormous number of messages each day for the past 17 years. The vast majority of today's messages are machine-generated (about 90% of the messages), based on a boilerplate with a small number of specific per-recipient changes. We show that the popular Zlib compression to gzip format fails to fully utilize the high similarity between these machine-generated...
Fisher vectors (FV) aggregated from local invariant features (e.g., SIFT) is one of the state-of-the-art descriptors for visual search, due to high discriminability but small visual vocabulary. Nevertheless, a high-dimensional FV needs to be compressed into a compact descriptor for light storage and high matching eficiency. In this paper, we formulate the FV compression as a resource-constrained optimization...
High efficiency video coding (HEVC) is an emerging video compression standard, developed by the Joint Collaborative Team on Video Coding (JCT-VC). The aim of HEVC standardization effort is to save about 50% bit rate for equal perceptual video quality relative to H.264/AVC. Although HEVC provides greater bit rate saving, it also brings the enormous encoding complexity increase. In this paper, we propose...
Background model can help to improve the compression efficiency for surveillance video coding, but the existing frame-based background model is inefficient in some situations, for example, when a region of background changes frequently or periodically. In this paper, a block-based background model is proposed to solve this problem. We save the background blocks recognized from each reconstructed frame...
This paper proposes an adaptive dictionary learning approach based on sub modular optimization. A candidate atom set is constructed based on multiple bases from the combination of analytic and trained dictionaries. With the low-frequency components by the analytic DCT atoms, high-resolution dictionaries can be inferred through online learning to make efficient approximation with rapid convergence...
To enable learning-based video coding for transmission over heterogenous networks, this paper proposes a scalable video coding framework by progressive dictionary learning. With the hierarchical B-picture prediction structure, the inter-predicted frames would be reconstructed in terms of the spatio-temporal dictionary in a successive sense. Within the progressive dictionary learning, the training...
Motion vectors of depth-maps in multiview and free-viewpoint videos exhibit strong spatial as well as inter-component clustering tendency. This paper presents a novel motion vector coding technique that first compresses the multidimensional bitmaps of macro block mode information and then encodes only the non-zero components of motion vectors. The bitmaps are partitioned into disjoint cuboids using...
Context transformations is a very simple data transformation method that we presented recently and it is used to decrease uncertainty in input data. The transformation is based on exchange of two different di-grams. This paper is focused on new consequences of the relationships discovered subsequently. We were able to find a mathematical model which predicts the efficiency of each transformation....
We propose a general framework for parallel entropy coding in media compression, which preserves compression efficiency, and is well matched to future generations of general-purpose or custom processors. Similarly to some previous parallelization methods, it is based on the fact that optimal compression is not affected by the arrangement of coded bits, but it goes further in exploiting the decreasing...
Compression is a key component in many imaging systems in order to accommodate limited resources such as power and bandwidth. Image compression is often done independent of the specific tasks that the systems are designed for, such as target detection, classification, diagnosis, etc. Standard compression techniques are designed based on quality metrics such as mean-squared error (MSE) or peak signal...
In this paper, a new block-transform-based image compression scheme is proposed by combining vector quantization (VQ) and two transformations, discrete cosine transform (DCT) and vector-embedded Karhunen-Loève transform (VEKLT). First, 8×8 blocks from an input image are normalized and vector-quantized. Then, the difference between the original block and its vector-quantized block is transformed by...
Automatic or semi-automatic stereoscopic image quality assessment has arisen due to the recent diffusion of a new generation of stereoscopic technologies and content demand. Thereby, there is a growth in asking for algorithms of Stereoscopic Image Quality Metrics (SIQA). In this paper, we present a method for assessing the stereoscopic image quality, QUALITAS. QUALITAS is grounded on some human visual...
This paper introduces a 2-D index map coding of the palette mode in screen content coding extension of the High-Efficiency Video Coding (HEVC SCC) standard to further improve the compression performance. In contrast to the current 1-D search using RUN to represent the length of matched string, we bring the block width and height to describe the arbitrary rectangle shape. We also use the block vector...
We propose an analytical model to estimate the depth-error-induced virtual view synthesis distortion (VVSD) in 3D video, taking into account the configuration of the cameras. Focusing on view synthesis under depth error, we carefully analyze the merging operations under different situations that affect pixel availability: overlapping region, disocclusion and boundary region, disparity error region,...
We present parallel algorithms for wavelet tree construction with polylogarithmic depth, improving upon the linear depth of the recent parallel algorithms by Fuentes-Sepulveda et al. We experimentally show that on a 40-core machine with two-way hyper-threading, we outperform the existing parallel algorithms by 1.3--5.6x and achieve up to 27x speedup over the sequential algorithm on a variety of real-world...
In this paper, we proposed a new rate control algorithm for High Efficiency Video Coding (HEVC), the latest video coding standard from the ITU/ISO. We use the information of pre-encoded 16x16 coding units (CUs) to estimate the characteristics of the largest coding unit (LCU). Based on the estimates, the proposed R -- λ model can be refined before the real encoding process. This is in...
In order to promote the development of auto-stereoscopic display, MPEG has proposed multi-view plus depth (MVD) format. The depth video is encoded and transmitted with color video to synthesize virtual views at the receiver side. The existing video coding standards such as H.264/AVC introduces coding artifacts along the depth boundaries, which may seriously affects the synthesized view quality and...
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