240 research outputs found
Multiplicative Multiresolution Decomposition for Lossless Volumetric Medical Images Compression
With the emergence of medical imaging, the compression of volumetric medical images is essential. For this purpose, we propose a novel Multiplicative Multiresolution Decomposition (MMD) wavelet coding scheme for lossless compression of volumetric medical images. The MMD is used in speckle reduction technique but offers some proprieties which can be exploited in compression. Thus, as the wavelet transform the MMD provides a hierarchical representation and offers a possibility to realize lossless compression. We integrate in proposed scheme an inter slice filter based on wavelet transform and motion compensation to reduce data energy efficiently. We compare lossless results of classical wavelet coders such as 3D SPIHT and JP3D to the proposed scheme. This scheme incorporates MMD in lossless compression technique by applying MMD/wavelet or MMD transform to each slice, after inter slice filter is employed and the resulting sub-bands are coded by the 3D zero-tree algorithm SPIHT. Lossless experimental results show that the proposed scheme with the MMD can achieve lowest bit rates compared to 3D SPIHT and JP3D
Efficient compression of motion compensated residuals
EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Motion estimation and signaling techniques for 2D+t scalable video coding
We describe a fully scalable wavelet-based 2D+t (in-band) video coding architecture. We propose new coding tools specifically designed for this framework aimed at two goals: reduce the computational complexity at the encoder without sacrificing compression; improve the coding efficiency, especially at low bitrates. To this end, we focus our attention on motion estimation and motion vector encoding. We propose a fast motion estimation algorithm that works in the wavelet domain and exploits the geometrical properties of the wavelet subbands. We show that the computational complexity grows linearly with the size of the search window, yet approaching the performance of a full search strategy. We extend the proposed motion estimation algorithm to work with blocks of variable sizes, in order to better capture local motion characteristics, thus improving in terms of rate-distortion behavior. Given this motion field representation, we propose a motion vector coding algorithm that allows to adaptively scale the motion bit budget according to the target bitrate, improving the coding efficiency at low bitrates. Finally, we show how to optimally scale the motion field when the sequence is decoded at reduced spatial resolution. Experimental results illustrate the advantages of each individual coding tool presented in this paper. Based on these simulations, we define the best configuration of coding parameters and we compare the proposed codec with MC-EZBC, a widely used reference codec implementing the t+2D framework
Coding of video with a single information plane
Mestrado em Engenharia ElectrĂłnica e TelecomunicaçõesAs actuais normas para codificação de vĂdeo, tais como os MPEG2/4 ou
H.263/4, foram desenvolvidas para codificação de vĂdeo com cor. A informação de cor
é representada usando um espaço apropriado, como, por
exemplo, o YCbCr. Estes espaços de cor sĂŁo constituĂdos por trĂŞs planos:
um para a dominância (no exemplo dado, o Y) e dois para a informação
de crominância (neste caso, o Cb e o Cr). Contudo, há aplicações onde a
informação a codificar é composta apenas por um plano de informação que
pode, por exemplo, representar nĂveis de cinzento em imagem mĂ©dica, ou
Ăndices para tabelas de cores. A motivação desta tese prende-se com dois
factos: a produção de imagens médicas em formato digital estar a crescer,
impondo técnicas eficazes para o tratamento e a compressão de dados e,
embora os modelos de cor indexada sejam há muito utilizados para representar
imagens, nĂŁo tĂŞm sido convenientemente explorados em vĂdeo. Com
esta dissertação pretende-se investigar novas estratégias de compressão sem
perdas que explorem a redundância entre imagens consecutivas que caracterizam
estas modalidades de imagem. Portanto, ao longo do trabalho
implementou-se dois codificadores de vĂdeo para um sĂł plano de informação,
baseados num modelo hĂbrido. Um deles utiliza codificação de Golomb e
o outro codificação aritmética, estudando-se assim a eficácia de cada um,
quer para a escala de cinzentos, quer para vĂdeos com tabela de cores indexadas.
Adicionalmente, para vĂdeos de cor indexada, implementou-se um
algoritmo de reordenação da tabela de cores, o que torna a codificação mais
eficaz.
ABSTRACT: The current standards for video encoding, such as MPEG2/4 or H.263/4,
have been developed for encoding video with color. The color information
is represented using an appropriate space, such as YCbCr. These color
spaces are made of three planes: one for luminance (in the given example,
the Y) and two for the chrominance information (in this case, the Cb and
Cr). However, there are applications where the information lies in a single
information plane that may, for example, represent shades of gray (medical
imaging) or indexes to color tables (color indexed video). The motivation
of this thesis is related with two points: the production of medical images
in digital format has been growing, imposing efficient techniques for the
treatment and compression of data and, although color indexed models have
been used for a long time to represent images, it has not been adequately
explored in video. With this thesis, we intended to investigate new strategies
for lossless compression which exploits the redundancy between consecutive
images that characterize these types of images. Therefore, during this work,
it has been implemented two video encoders with one information plane,
based on a hybrid model. One of them uses Golomb codes and the other
arithmetic coding. It has been studied the efficiency of each one, both using
gray scale and color indexed videos. In addition, for color indexed videos, it
has been implemented a palette reordering algorithm, making the encoding
more efficient
- …