964 research outputs found
Lossless Image and Intra-frame Compression with Integer-to-Integer DST
Video coding standards are primarily designed for efficient lossy
compression, but it is also desirable to support efficient lossless compression
within video coding standards using small modifications to the lossy coding
architecture. A simple approach is to skip transform and quantization, and
simply entropy code the prediction residual. However, this approach is
inefficient at compression. A more efficient and popular approach is to skip
transform and quantization but also process the residual block with DPCM, along
the horizontal or vertical direction, prior to entropy coding. This paper
explores an alternative approach based on processing the residual block with
integer-to-integer (i2i) transforms. I2i transforms can map integer pixels to
integer transform coefficients without increasing the dynamic range and can be
used for lossless compression. We focus on lossless intra coding and develop
novel i2i approximations of the odd type-3 DST (ODST-3). Experimental results
with the HEVC reference software show that the developed i2i approximations of
the ODST-3 improve lossless intra-frame compression efficiency with respect to
HEVC version 2, which uses the popular DPCM method, by an average 2.7% without
a significant effect on computational complexity.Comment: Draft consisting of 16 page
Deep Learning-Based Video Coding: A Review and A Case Study
The past decade has witnessed great success of deep learning technology in
many disciplines, especially in computer vision and image processing. However,
deep learning-based video coding remains in its infancy. This paper reviews the
representative works about using deep learning for image/video coding, which
has been an actively developing research area since the year of 2015. We divide
the related works into two categories: new coding schemes that are built
primarily upon deep networks (deep schemes), and deep network-based coding
tools (deep tools) that shall be used within traditional coding schemes or
together with traditional coding tools. For deep schemes, pixel probability
modeling and auto-encoder are the two approaches, that can be viewed as
predictive coding scheme and transform coding scheme, respectively. For deep
tools, there have been several proposed techniques using deep learning to
perform intra-picture prediction, inter-picture prediction, cross-channel
prediction, probability distribution prediction, transform, post- or in-loop
filtering, down- and up-sampling, as well as encoding optimizations. In the
hope of advocating the research of deep learning-based video coding, we present
a case study of our developed prototype video codec, namely Deep Learning Video
Coding (DLVC). DLVC features two deep tools that are both based on
convolutional neural network (CNN), namely CNN-based in-loop filter (CNN-ILF)
and CNN-based block adaptive resolution coding (CNN-BARC). Both tools help
improve the compression efficiency by a significant margin. With the two deep
tools as well as other non-deep coding tools, DLVC is able to achieve on
average 39.6\% and 33.0\% bits saving than HEVC, under random-access and
low-delay configurations, respectively. The source code of DLVC has been
released for future researches
Integer Discrete Flows and Lossless Compression
Lossless compression methods shorten the expected representation size of data
without loss of information, using a statistical model. Flow-based models are
attractive in this setting because they admit exact likelihood optimization,
which is equivalent to minimizing the expected number of bits per message.
However, conventional flows assume continuous data, which may lead to
reconstruction errors when quantized for compression. For that reason, we
introduce a flow-based generative model for ordinal discrete data called
Integer Discrete Flow (IDF): a bijective integer map that can learn rich
transformations on high-dimensional data. As building blocks for IDFs, we
introduce a flexible transformation layer called integer discrete coupling. Our
experiments show that IDFs are competitive with other flow-based generative
models. Furthermore, we demonstrate that IDF based compression achieves
state-of-the-art lossless compression rates on CIFAR10, ImageNet32, and
ImageNet64. To the best of our knowledge, this is the first lossless
compression method that uses invertible neural networks.Comment: Accepted as a conference paper at Neural Information Processing
Systems (NeurIPS) 201
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
Entropy Encoding, Hilbert Space and Karhunen-Loeve Transforms
By introducing Hilbert space and operators, we show how probabilities,
approximations and entropy encoding from signal and image processing allow
precise formulas and quantitative estimates. Our main results yield orthogonal
bases which optimize distinct measures of data encoding.Comment: 25 pages, 1 figur
Image compression overview
Compression plays a significant role in a data storage and a transmission. If
we speak about a generall data compression, it has to be a lossless one. It
means, we are able to recover the original data 1:1 from the compressed file.
Multimedia data (images, video, sound...), are a special case. In this area, we
can use something called a lossy compression. Our main goal is not to recover
data 1:1, but only keep them visually similar. This article is about an image
compression, so we will be interested only in image compression. For a human
eye, it is not a huge difference, if we recover RGB color with values
[150,140,138] instead of original [151,140,137]. The magnitude of a difference
determines the loss rate of the compression. The bigger difference usually
means a smaller file, but also worse image quality and noticable differences
from the original image. We want to cover compression techniques mainly from
the last decade. Many of them are variations of existing ones, only some of
them uses new principes
A Fast and Efficient Near-Lossless Image Compression using Zipper Transformation
Near-lossless image compression-decompression scheme is proposed in this
paper using Zipper Transformation (ZT) and inverse zipper transformation (iZT).
The proposed ZT exploits the conjugate symmetry property of Discrete Fourier
Transformation (DFT). The proposed transformation is implemented using two
different configurations: the interlacing and concatenating ZT. In order to
quantify the efficacy of the proposed transformation, we benchmark with
Discrete Cosine Transformation (DCT) and Fast Walsh Hadamard Transformation
(FWHT) in terms of lossless compression capability and computational cost.
Numerical simulations show that ZT-based compression algorithm is
near-lossless, compresses better, and offers faster implementation than both
DCT and FWHT. Also, interlacing and concatenating ZT are shown to yield similar
results in most of the test cases considered
A Practical Approach to Lossy Joint Source-Channel Coding
This work is devoted to practical joint source channel coding. Although the
proposed approach has more general scope, for the sake of clarity we focus on a
specific application example, namely, the transmission of digital images over
noisy binary-input output-symmetric channels. The basic building blocks of most
state-of the art source coders are: 1) a linear transformation; 2) scalar
quantization of the transform coefficients; 3) probability modeling of the
sequence of quantization indices; 4) an entropy coding stage. We identify the
weakness of the conventional separated source-channel coding approach in the
catastrophic behavior of the entropy coding stage. Hence, we replace this stage
with linear coding, that maps directly the sequence of redundant quantizer
output symbols into a channel codeword. We show that this approach does not
entail any loss of optimality in the asymptotic regime of large block length.
However, in the practical regime of finite block length and low decoding
complexity our approach yields very significant improvements. Furthermore, our
scheme allows to retain the transform, quantization and probability modeling of
current state-of the art source coders, that are carefully matched to the
features of specific classes of sources. In our working example, we make use of
``bit-planes'' and ``contexts'' model defined by the JPEG2000 standard and we
re-interpret the underlying probability model as a sequence of conditionally
Markov sources. The Markov structure allows to derive a simple successive
coding and decoding scheme, where the latter is based on iterative Belief
Propagation. We provide a construction example of the proposed scheme based on
punctured Turbo Codes and we demonstrate the gain over a conventional separated
scheme by running extensive numerical experiments on test images.Comment: 51 pages, submitted to IEEE Transactions on Information Theor
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