162 research outputs found
Distributed video coding for wireless video sensor networks: a review of the state-of-the-art architectures
Distributed video coding (DVC) is a relatively new video coding architecture originated from two fundamental theorems namely, Slepian–Wolf and Wyner–Ziv. Recent research developments have made DVC attractive for applications in the emerging domain of wireless video sensor networks (WVSNs). This paper reviews the state-of-the-art DVC architectures with a focus on understanding their opportunities and gaps in addressing the operational requirements and application needs of WVSNs
Zerotree-based stereoscopic video CODEC
Due to the provision of a more natural representation of a
scene in the form of left and right eye views, a stereoscopic imaging
system provides a more effective method for image/video display. Unfortunately
the vast amount of information that must be transmitted/stored
to represent a stereo image pair/video sequence, has so far hindered its
use in commercial applications. However, by properly exploiting the spatial,
temporal and binocular redundancy, a stereo image pair or a sequence
could be compressed and transmitted through a single monocular
channel’s bandwidth without unduly sacrificing the perceived
stereoscopic image quality. We propose a timely and novel framework to
transmit stereoscopic data efficiently. We propose a timely and novel
framework to transmit stereoscopic data efficiently. We present a new
technique for coding stereo video sequences based on discrete wavelet
transform DWT technology. The proposed technique particularly exploits
zerotree entropy ZTE coding that makes use of the wavelet block
concept to achieve low bit rate stereo video coding. One of the two
image streams, namely, the main stream, is independently coded by a
zerotree video CODEC, while the second stream, namely, the auxiliary
stream, is predicted based on disparity compensation. A zerotree video
CODEC subsequently codes the residual stream. We compare the performance
of the proposed CODEC with a discrete cosine transform
DCT -based, modified MPEG-2 stereo video CODEC. We show that the
proposed CODEC outperforms the benchmark CODEC in coding both
main and auxiliary streams
Hyperspectral image compression : adapting SPIHT and EZW to Anisotropic 3-D Wavelet Coding
Hyperspectral images present some specific characteristics that should be used by an efficient compression system. In compression, wavelets have shown a good adaptability to a wide range of data, while being of reasonable complexity. Some wavelet-based compression algorithms have been successfully used for some hyperspectral space missions. This paper focuses on the optimization of a full wavelet compression system for hyperspectral images. Each step of the compression algorithm is studied and optimized. First, an algorithm to find the optimal 3-D wavelet decomposition in a rate-distortion sense is defined. Then, it is shown that a specific fixed decomposition has almost the same performance, while being more useful in terms of complexity issues. It is shown that this decomposition significantly improves the classical isotropic decomposition. One of the most useful properties of this fixed decomposition is that it allows the use of zero tree algorithms. Various tree structures, creating a relationship between coefficients, are compared. Two efficient compression methods based on zerotree coding (EZW and SPIHT) are adapted on this near-optimal decomposition with the best tree structure found. Performances are compared with the adaptation of JPEG 2000 for hyperspectral images on six different areas presenting different statistical properties
Image Compression by Wavelet Transform.
Digital images are widely used in computer applications. Uncompressed digital images require considerable storage capacity and transmission bandwidth. Efficient image compression solutions are becoming more critical with the recent growth of data intensive, multimedia-based web applications.
This thesis studies image compression with wavelet transforms. As a necessary background, the basic concepts of graphical image storage and currently used compression algorithms are discussed. The mathematical properties of several types of wavelets, including Haar, Daubechies, and biorthogonal spline wavelets are covered and the Enbedded Zerotree Wavelet (EZW) coding algorithm is introduced. The last part of the thesis analyzes the compression results to compare the wavelet types
Rate-distortion adaptive vector quantization for wavelet imagecoding
We propose a wavelet image coding scheme using rate-distortion adaptive tree-structured residual vector quantization. Wavelet transform coefficient coding is based on the pyramid hierarchy (zero-tree), but rather than determining the zero-tree relation from the coarsest subband to the finest by hard thresholding, the prediction in our scheme is achieved by rate-distortion optimization with adaptive vector quantization on the wavelet coefficients from the finest subband to the coarsest. The proposed method involves only integer operations and can be implemented with very low computational complexity. The preliminary experiments have shown some encouraging results: a PSNR of 30.93 dB is obtained at 0.174 bpp on the test image LENA (512×512
Wavelet Based Image Coding Schemes : A Recent Survey
A variety of new and powerful algorithms have been developed for image
compression over the years. Among them the wavelet-based image compression
schemes have gained much popularity due to their overlapping nature which
reduces the blocking artifacts that are common phenomena in JPEG compression
and multiresolution character which leads to superior energy compaction with
high quality reconstructed images. This paper provides a detailed survey on
some of the popular wavelet coding techniques such as the Embedded Zerotree
Wavelet (EZW) coding, Set Partitioning in Hierarchical Tree (SPIHT) coding, the
Set Partitioned Embedded Block (SPECK) Coder, and the Embedded Block Coding
with Optimized Truncation (EBCOT) algorithm. Other wavelet-based coding
techniques like the Wavelet Difference Reduction (WDR) and the Adaptive Scanned
Wavelet Difference Reduction (ASWDR) algorithms, the Space Frequency
Quantization (SFQ) algorithm, the Embedded Predictive Wavelet Image Coder
(EPWIC), Compression with Reversible Embedded Wavelet (CREW), the Stack-Run
(SR) coding and the recent Geometric Wavelet (GW) coding are also discussed.
Based on the review, recommendations and discussions are presented for
algorithm development and implementation.Comment: 18 pages, 7 figures, journa
High ratio wavelet video compression through real-time rate-distortion estimation.
Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.The success of the wavelet transform in the compression of still images has prompted an
expanding effort to exercise this transform in the compression of video. Most existing video
compression methods incorporate techniques from still image compression, such techniques
being abundant, well defined and successful. This dissertation commences with a thorough
review and comparison of wavelet still image compression techniques. Thereafter an
examination of wavelet video compression techniques is presented. Currently, the most
effective video compression system is the DCT based framework, thus a comparison between
these and the wavelet techniques is also given.
Based on this review, this dissertation then presents a new, low-complexity, wavelet video
compression scheme. Noting from a complexity study that the generation of temporally
decorrelated, residual frames represents a significant computational burden, this scheme uses
the simplest such technique; difference frames. In the case of local motion, these difference
frames exhibit strong spatial clustering of significant coefficients. A simple spatial syntax is
created by splitting the difference frame into tiles. Advantage of the spatial clustering may then
be taken by adaptive bit allocation between the tiles. This is the central idea of the method.
In order to minimize the total distortion of the frame, the scheme uses the new p-domain rate-distortion
estimation scheme with global numerical optimization to predict the optimal
distribution of bits between tiles. Thereafter each tile is independently wavelet transformed and
compressed using the SPIHT technique.
Throughout the design process computational efficiency was the design imperative, thus leading
to a real-time, software only, video compression scheme. The scheme is finally compared to
both the current video compression standards and the leading wavelet schemes from the
literature in terms of computational complexity visual quality. It is found that for local motion
scenes the proposed algorithm executes approximately an order of magnitude faster than these
methods, and presents output of similar quality. This algorithm is found to be suitable for
implementation in mobile and embedded devices due to its moderate memory and
computational requirements
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