19 research outputs found
Selection of Wavelet Basis Function for Image Compression : a Review
Wavelets are being suggested as a platform for various tasks in image processing. The advantage of wavelets lie in its time frequency resolution. The use of different basis functions in the form of different wavelets made the wavelet analysis as a destination for many applications. The performance of a particular technique depends on the wavelet coefficients arrived after applying the wavelet transform. The coefficients for a specific input signal depends on the basis functions used in the wavelet transform. Hence in this paper toward this end, different basis functions and their features are presented. As the image compression task depends on wavelet transform to large extent from few decades, the selection of basis function for image compression should be taken with care. In this paper, the factors influencing the performance of image compression are presented
Progressive transmission of medical images
A novel adaptive source-channel coding scheme for progressive transmission of medical images with a feedback system is therefore proposed in this dissertation. The overall design includes Discrete Wavelet Transform (DWT), Embedded Zerotree Wavelet (EZW) coding, Joint Source-Channel Coding (JSCC), prioritization of region of interest (RoI), variability of parity length based on feedback, and the corresponding hardware design utilising Simulink. The JSCC can achieve an efficient transmission by incorporating unequal error projection (UEP) and rate allocation. An algorithm is also developed to estimate the number of erroneous data in the receiver. The algorithm detects the address in which the number of symbols for each subblock is indicated, and reassigns an estimated correct data according to a decision making criterion, if error data is detected. The proposed system has been designed based on Simulink which can be used to generate netlist for portable devices. A new compression method called Compressive Sensing (CS) is also revisited in this work. CS exhibits many advantages in comparison with EZW based on our experimental results. DICOM JPEG2000 is an efficient coding standard for lossy or lossless multi-component image coding. However, it does not provide any mechanism for automatic RoI definition, and is more complex compared to our proposed scheme. The proposed system significantly reduces the transmission time, lowers computation cost, and maintains an error-free state in the RoI with regards to the above provided features. A MATLAB-based TCP/IP connection is established to demonstrate the efficacy of the proposed interactive and adaptive progressive transmission system. The proposed system is simulated for both binary and symmetric channel (BSC) and Rayleigh channel. The experimental results confirm the effectiveness of the design.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Progressive transmission of medical images
A novel adaptive source-channel coding scheme for progressive transmission of medical images with a feedback system is therefore proposed in this dissertation. The overall design includes Discrete Wavelet Transform (DWT), Embedded Zerotree Wavelet (EZW) coding, Joint Source-Channel Coding (JSCC), prioritization of region of interest (RoI), variability of parity length based on feedback, and the corresponding hardware design utilising Simulink. The JSCC can achieve an efficient transmission by incorporating unequal error projection (UEP) and rate allocation. An algorithm is also developed to estimate the number of erroneous data in the receiver. The algorithm detects the address in which the number of symbols for each subblock is indicated, and reassigns an estimated correct data according to a decision making criterion, if error data is detected. The proposed system has been designed based on Simulink which can be used to generate netlist for portable devices. A new compression method called Compressive Sensing (CS) is also revisited in this work. CS exhibits many advantages in comparison with EZW based on our experimental results. DICOM JPEG2000 is an efficient coding standard for lossy or lossless multi-component image coding. However, it does not provide any mechanism for automatic RoI definition, and is more complex compared to our proposed scheme. The proposed system significantly reduces the transmission time, lowers computation cost, and maintains an error-free state in the RoI with regards to the above provided features. A MATLAB-based TCP/IP connection is established to demonstrate the efficacy of the proposed interactive and adaptive progressive transmission system. The proposed system is simulated for both binary and symmetric channel (BSC) and Rayleigh channel. The experimental results confirm the effectiveness of the desig
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
Wavelet based image compression integrating error protection via arithmetic coding with forbidden symbol and map metric sequential decoding with ARQ retransmission
The phenomenal growth of digital multimedia applications has forced the communication
The JPEG2000 still image coding system: An overview
With the increasing use of multimedia technologies, image compression requires higher performance as well as new features. To address this need in the specific area of still image encoding, a new standard is currently being developed, the JPEG2000. It is not only intended to provide rate-distortion and subjective image quality performance superior to existing standards, but also to provide features and functionalities that current standards can either not address efficiently or in many cases cannot address at all. Lossless and lossy compression, embedded lossy to lossless coding, progressive transmission by pixel accuracy and by resolution, robustness to the presence of bit-errors and region-of-interest coding, are some representative features. It is interesting to note that JPEG2000 is being designed to address the requirements of a diversity of applications, e.g. Internet, color facsimile, printing, scanning, digital photography, remote sensing, mobile applications, medical imagery, digital library and E-commerce
Compression of Three-Dimensional Magnetic Resonance Brain Images.
Losslessly compressing a medical image set with multiple slices is paramount in radiology since all the information within a medical image set is crucial for both diagnosis and treatment. This dissertation presents a novel and efficient diagnostically lossless compression scheme (predicted wavelet lossless compression method) for sets of magnetic resonance (MR) brain images, which are called 3-D MR brain images. This compression scheme provides 3-D MR brain images with the progressive and preliminary diagnosis capabilities. The spatial dependency in 3-D MR brain images is studied with histograms, entropy, correlation, and wavelet decomposition coefficients. This spatial dependency is utilized to design three kinds of predictors, i.e., intra-, inter-, and intra-and-inter-slice predictors, that use the correlation among neighboring pixels. Five integer wavelet transformations are applied to the prediction residues. It shows that the intra-slice predictor 3 using a x-pixel and a y-pixel for prediction plus the 1st-level (2, 2) interpolating integer wavelet with run-length and arithmetic coding achieves the best compression. An automated threshold based background noise removal technique is applied to remove the noise outside the diagnostic region. This preprocessing method improves the compression ratio of the proposed compression technique by approximately 1.61 times. A feature vector based approach is used to determine the representative slice with the most discernible brain structures. This representative slice is progressively encoded by a lossless embedded zerotree wavelet method. A rough version of this representative slice is gradually transmitted at an increasing bit rate so the validity of the whole set can be determined early. This feature vector based approach is also utilized to detect multiple sclerosis (MS) at an early stage. Our compression technique with the progressive and preliminary diagnosis capability is tested with simulated and real 3-D MR brain image sets. The compression improvement versus the best commonly used lossless compression method (lossless JPEG) is 41.83% for simulated 3-D MR brain image sets and 71.42% for real 3-D MR brain image sets. The accuracy of the preliminary MS diagnosis is 66.67% based on six studies with an expert radiologist\u27s diagnosis
On the design of fast and efficient wavelet image coders with reduced memory usage
Image compression is of great importance in multimedia systems and
applications because it drastically reduces bandwidth requirements for
transmission and memory requirements for storage. Although earlier
standards for image compression were based on the Discrete Cosine
Transform (DCT), a recently developed mathematical technique, called
Discrete Wavelet Transform (DWT), has been found to be more efficient
for image coding.
Despite improvements in compression efficiency, wavelet image coders
significantly increase memory usage and complexity when compared with
DCT-based coders. A major reason for the high memory requirements is
that the usual algorithm to compute the wavelet transform requires the
entire image to be in memory. Although some proposals reduce the memory
usage, they present problems that hinder their implementation. In
addition, some wavelet image coders, like SPIHT (which has become a
benchmark for wavelet coding), always need to hold the entire image in
memory.
Regarding the complexity of the coders, SPIHT can be considered quite
complex because it performs bit-plane coding with multiple image scans.
The wavelet-based JPEG 2000 standard is still more complex because it
improves coding efficiency through time-consuming methods, such as an
iterative optimization algorithm based on the Lagrange multiplier
method, and high-order context modeling.
In this thesis, we aim to reduce memory usage and complexity in
wavelet-based image coding, while preserving compression efficiency. To
this end, a run-length encoder and a tree-based wavelet encoder are
proposed. In addition, a new algorithm to efficiently compute the
wavelet transform is presented. This algorithm achieves low memory
consumption using line-by-line processing, and it employs recursion to
automatically place the order in which the wavelet transform is
computed, solving some synchronization problems that have not been
tackled by previous proposals. The proposed encodeOliver Gil, JS. (2006). On the design of fast and efficient wavelet image coders with reduced memory usage [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/1826Palanci
Research and developments of distributed video coding
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The recent developed Distributed Video Coding (DVC) is typically suitable for the applications such as wireless/wired video sensor network, mobile camera etc. where the traditional video coding standard is not feasible due to the constrained computation at the encoder. With DVC, the computational burden is moved from encoder to decoder. The compression efficiency is achieved via joint decoding at the decoder. The practical application of DVC is referred to Wyner-Ziv video coding (WZ) where the side information is available at the decoder to perform joint decoding. This join decoding inevitably causes a very complex decoder. In current WZ video coding issues, many of them emphasise how to improve the system coding performance but neglect the huge complexity caused at the decoder. The complexity of the decoder has direct influence to the system output. The beginning period of this research targets to optimise the decoder in pixel domain WZ video coding (PDWZ), while still achieves similar compression performance. More specifically, four issues are raised to optimise the input block size, the side information generation, the side information refinement process and the feedback channel respectively.
The transform domain WZ video coding (TDWZ) has distinct superior performance to the normal PDWZ due to the exploitation in spatial direction during the encoding. However, since there is no motion estimation at the encoder in WZ video coding, the temporal correlation is not exploited at all at the encoder in all current WZ video coding issues. In the middle period of this research, the 3D DCT is adopted in the TDWZ to remove redundancy in both spatial and temporal direction thus to provide even higher coding performance. In the next step of this research, the performance of transform domain Distributed Multiview Video Coding (DMVC) is also investigated. Particularly, three types transform domain DMVC frameworks which are transform domain DMVC using TDWZ based 2D DCT, transform domain DMVC using TDWZ based on 3D DCT and transform domain residual DMVC using TDWZ based on 3D DCT are investigated respectively.
One of the important applications of WZ coding principle is error-resilience. There have been several attempts to apply WZ error-resilient coding for current video coding standard e.g. H.264/AVC or MEPG 2. The final stage of this research is the design of WZ error-resilient
scheme for wavelet based video codec. To balance the trade-off between error resilience ability and bandwidth consumption, the proposed scheme emphasises the protection of the Region of Interest (ROI) area. The efficiency of bandwidth utilisation is achieved by mutual efforts of WZ coding and sacrificing the quality of unimportant area. In summary, this research work contributed to achieves several advances in WZ video coding. First of all, it is targeting to build an efficient PDWZ with optimised decoder. Secondly, it aims to build an advanced TDWZ based on 3D DCT, which then is applied into multiview video coding to realise advanced transform domain DMVC. Finally, it aims to design an efficient error-resilient scheme for wavelet video codec, with which the trade-off between bandwidth consumption and error-resilience can be better balanced