Английские материалы
|
| Авторы |
Название статьи |
Описание |
Рейтинг |
| Dzung T. Hoang, Philip M. Long, and Jeffrey Scott Vitter, Fellow |
Efficient Cost Measures for Motion Estimation at Low Bit Rates |
Abstract— We present and compare methods for choosing
motion vectors for block-based motion-compensated video coding.
The primary focus is on videophone and videoconferencing
applications, where low bit rates are necessary, where motion
is usually limited, and where the amount of computation is
also limited. In a typical block-based motion-compensated video
coding system, motion vectors are transmitted along with a lossy
encoding of the residuals. As the bit rate decreases, the proportion
required to transmit the motion vectors increases. We provide
experimental evidence that choosing motion vectors explicitly
to minimize rate (including motion vector coding), subject to
implicit constraints on distortion, yields better rate–distortion
tradeoffs than minimizing some measure of prediction error.
RAR 474 кбайт |
?
|
| John C.-H. Ju, Yen-Kuang Chen, and S. Y. Kung |
A Fast Rate-Optimized Motion Estimation Algorithm for Low-Bit-Rate Video Coding |
Abstract—Motion estimation is known to be the main bottleneck
in real-time encoding applications, and the search for an
effective motion estimation algorithm (in terms of computational
complexity and compression efficiency) has been a challenging
problem for years. This paper describes a new block-matching
algorithm that is much faster than the full search algorithm and
occasionally even produces better rate-distortion curves than the
full search algorithms. We observe that a piecewise continuous
motion field reduces the bit rate for differentially encoded motion
vectors. Our motion estimation algorithm exploits the spatial
correlations of motion vectors effectively in the sense of producing
better rate-distortion curves. Furthermore, we incorporate
such correlations in a multiresolution framework to reduce the
computational complexity. Simulation shows that this method is
successful because of the homogeneous and reliable estimation
of the displacement vectors. In nine out of our ten benchmark
simulations, the performance of the full search algorithm and
that of our subblock multiresolution method is about the same.
In one out of our ten benchmark simulations, our method has
improvement.
RAR 316 кбайт |
?
|
| Jorge Sastre, Antonio Ferreras, and Josй Fйlix Hernбndez-Gil |
Motion Vector Size-Compensation Based Method for Very Low Bit-Rate Video Coding |
Abstract—In this paper, a new method to achieve better
compression efficiency in low bit-rate video coding is proposed.
It is based on a global bit-rate reduction at a macroblock level,
optimizing the number of bits to code each macroblock as a whole
by means of motion vector and headers size compensation. The
selection of the best motion vector and different coding modes for
each block of the current picture will be made depending not only
on trying to choose the best prediction for the block, but also on
the number of bits to code the associate headers, introducing some
kind of penalization in the cost function. This method improves
efficiency on video compression for all qualities, but especially
for low-quality video coding, whose efficiency improvement can
reach 17%. Its implementation is simple, and compatible with
most video-compression standards (H.263, MPEG, etc.). Results
of the algorithm in a state-of-the-art H.263+ codec are presented,
and demonstrate that the efficiency enhancement is achieved with
minimal time-processing increase, and even decrease, in some
conditions.
RAR 440 кбайт
|
?
|
| Gopal Lakhani and Norman Zhong |
Derivation of Prediction Equations for Blocking Effect Reduction |
Abstract—In [1], a heuristic is proposed to solve an optimization
problem on reduction of blocking effects seen in low bit-rate
coded images. This paper presents a novel solution to the same
problem. Not only does it compute the global minimum, but
its computational complexity is significantly smaller as well.
The solution is stated in the form of prediction equations for
computation of certain discrete cosine transform coefficients—an
approach adapted by JPEG for its block-smoothing method.
Experimental results show that our solution outperforms JPEG’s
method.
RAR 150 кбайт
|
?
|
| Jorge Sastre, Antonio Ferreras, and Josй Fйlix Hernбndez-Gil |
Motion Vector Size-Compensation Based Method for Very Low Bit-Rate Video Coding |
Abstract—In this paper, a new method to achieve better
compression efficiency in low bit-rate video coding is proposed.
It is based on a global bit-rate reduction at a macroblock level,
optimizing the number of bits to code each macroblock as a whole
by means of motion vector and headers size compensation. The
selection of the best motion vector and different coding modes for
each block of the current picture will be made depending not only
on trying to choose the best prediction for the block, but also on
the number of bits to code the associate headers, introducing some
kind of penalization in the cost function. This method improves
efficiency on video compression for all qualities, but especially
for low-quality video coding, whose efficiency improvement can
reach 17%. Its implementation is simple, and compatible with
most video-compression standards (H.263, MPEG, etc.). Results
of the algorithm in a state-of-the-art H.263+ codec are presented,
and demonstrate that the efficiency enhancement is achieved with
minimal time-processing increase, and even decrease, in some
conditions.
RAR 440 кбайт
|
?
|
| Guoliang Fan, and Wai-Kuen Cham |
Model-Based Edge Reconstruction for Low Bit-Rate Wavelet-Compressed Images |
Abstract—At low bit rates, wavelet-based image coding is superior
to most traditional block-based methods in terms of visibility
and severity of coding artifacts in coded images. However, the compressed
images still suffer from obvious distortions around sharp
edges, which are perceptually objectionable. In order to improve
image quality for low bit-rate wavelet-based image coding, we proposed
a model-based edge-reconstruction algorithm for recovering
the lossy edges in coded images. Our approach applies a general
model to represent varieties of edges existing in an image. Based on
this model, the edge degradation process due to quantization errors
of wavelet coefficients is analyzed with the characterization of two
kinds of artifacts at edges.We develop two operations, model-based
edge approximation and Gaussian smoothing, to reconstruct distorted
edges by reducing both artifacts respectively. The proposed
method is able to improve image quality in terms of both visual
perception and image fidelity (peak signal-to-noise ratio) for most
images coded by wavelet-based methods at low bit-rates.
RAR 346 кбайт
|
?
|
| Beong-Jo Kim, Zixiang Xiong, and William A. Pearlman, Fellow |
Low Bit-Rate Scalable Video Coding with 3-D Set Partitioning in Hierarchical Trees (3-D SPIHT) |
Abstract—In this paper, we propose a low bit-rate embedded
video coding scheme that utilizes a 3-D extension of the set partitioning
in hierarchical trees (SPIHT) algorithm which has proved
so successful in still image coding. Three-dimensional spatio-temporal
orientation trees coupled with powerful SPIHT sorting and
refinement renders 3-D SPIHT video coder so efficient that it provides
comparable performance to H.263 objectively and subjectively
when operated at the bit rates of 30 to 60 kbits/s with minimal
system complexity. Extension to color-embedded video coding
is accomplished without explicit bit allocation, and can be used
for any color plane representation. In addition to being rate scalable,
the proposed video coder allows multiresolutional scalability
in encoding and decoding in both time and space from one bit
stream. This added functionality along with many desirable attributes,
such as full embeddedness for progressive transmission,
precise rate control for constant bit-rate traffic, and lowcomplexity
for possible software-only video applications, makes the proposed
video coder an attractive candidate for multimedia applications.
RAR 342 кбайт
|
?
|
| Wee Sun Lee, Mark R. Pickering, Michael R. Frater, and John F. Arnold |
A Robust Codec for Transmission of Very Low Bit-Rate Video over Channels with Bursty Errors |
Abstract—We describe a robust codec for the transmission of
very low bit-rate video over channels with a variety of errors, including
random and bursty bit errors and packet loss. The codec
exploits adaptivity to give good performance with a low overhead.
By only protecting macroblocks which would otherwise be poorly
concealed by the decoder, the codec allows adaptive selection of the
parts of video to protect. For protection, it uses multiple description
codes which indirectly provide frequency-based adaptivity by
protecting the more significant DCT coefficients. Simulations show
significant improvements in the performance of the codec when
compared to codecs which use intra macroblock updating (raster
scan and random) at the same overhead. The codec is efficient in
its use of bits and has good error resilience properties both objectively
and subjectively over a wide range of conditions. Further,
transcoding of the received bit stream to the standard H.263 syntax
is relatively easy.
RAR 225 кбайт
|
?
|
| Detlev Marpe and Hans L. Cycon |
Very Low Bit-Rate Video Coding Using Wavelet-Based Techniques |
Abstract—In this paper, we propose a very low bit-rate video
coding scheme based on a discrete wavelet transform (DWT),
block-matching motion estimation (BME), and overlapped block
motion compensation (OBMC). Our approach reveals that the
coding process works more efficiently if the quantized wavelet
coefficients are preprocessed by a mechanism exploiting the
redundancies in the wavelet subband structure. Thus, we introduce
a new framework of precoding techniques based on
the concepts of partitioning, aggregation, and conditional coding
(PACC). Our experimental results show that our PACC coder
outperforms the VM (Version 5.1) of MPEG4 both for the coding
of intraframes (1–2 dB PSNR) and residual frames (up to 1.5 dB
PSNR) of typical MPEG4 test sequences. The subjective quality
of reconstructed video is, in general, superior to that obtained
from the VM implementation. In addition, when restricted to the
intraframe mode, the proposed coding algorithm produces results
which are among the best reported for still image compression.
RAR 741 кбайт
|
?
|
| Jozsef Vass, Bing-Bing Chai, Kannappan Palaniappan, and Xinhua Zhuang |
Significance-Linked Connected Component Analysis for Very Low Bit-Rate Wavelet Video Coding |
Abstract—In recent years, a tremendous success in wavelet
image coding has been achieved. It is mainly attributed to
innovative strategies for data organization and representation of
wavelet-transformed images. However, there have been only a few
successful attempts in wavelet video coding. The most successful
is perhaps Sarnoff Corp.’s zerotree entropy (ZTE) video coder.
In this paper, a novel hybrid wavelet video coding algorithm
termed video significance-linked connected component analysis
(VSLCCA) is developed for very low bit-rate applications. There
also has been empirical evidence that wavelet transform combined
with those innovative data organization and representation
strategies can be an invaluable asset in very low bit-rate video
coding as long as motion compensated error frames are ensured
to be free of blocking effect or coherent.
In the proposed VSLCCA codec, first, fine-tuned motion estimation
based on the H.263 Recommendation is developed to
reduce temporal redundancy, and exhaustive overlapped block
motion compensation is utilized to ensure coherency in motion
compensated error frames. Second, wavelet transform is applied
to each coherent motion compensated error frame to attain
global energy compaction. Third, significant fields of wavelettransformed
error frames are organized and represented as
significance-linked connected components so that both the withinsubband
clustering and the cross-scale dependency are exploited.
Last, the horizontal and vertical components of motion vectors
are encoded separately using adaptive arithmetic coding while
significant wavelet coefficients are encoded in bit-plane order
by using high order Markov source modeling and adaptive
arithmetic coding.
Experimental results on eight standard MPEG-4 test sequences
show that for intraframe coding, on average the proposed codec
exceeds H.263 and ZTE in peak signal-to-noise ratio by as much
as 2.07 and 1.38 dB at 28 kbits, respectively. For entire sequence
coding, VSLCCA is superior to H.263 and ZTE by 0.35 and 0.71
dB on average, respectively.
RAR 894 кбайт
|
?
|
| Sangyoun Lee and Vijay K. Madisetti |
Parameter Optimization of Robust Low-Bit-Rate Video Coders |
Abstract—Most standards provide a generalized syntax and
semantics framework for video coders, leaving the selection and
optimization of the right parameter set (and lookup tables) to
the implementation. The choice of the right parameter set that is
suitable for a rich enough class of input sequences is, however,
quite difficult. This difficulty is particularly amplified in the lowbit-
rate video coding arena, where robust parameter sets are very
important. We propose that robust parameter estimation, using
the Taguchi methods, when applied to low-bit-rate video coding
allows effective (near optimal) performance over a wide variety of
input data streams. A number of experimental results confirm the
improvement (via robustness) vis-`a-vis conventional parameter
estimation methods, and these methods promise a solution to the
design of efficient parameter sets that support standards.
RAR 172 кбайт
|
?
|
| Seung Chul Yoon, Krishna Ratakonda, and Narendra Ahuja, Fellow |
Low Bit-Rate Video Coding with Implicit Multiscale Segmentation |
Abstract— In this paper, we report on our efforts toward
developing a multiscale segmentation based video compression
algorithm aimed at very low bit-rate applications such as video
teleconferencing and video phones.We introduce novel techniques
for multiscale segmentation based motion compensation and
residual coding. Our region based forward motion compensation
strategy (in terms of direction of motion vector, which is from
the previous frame to the current frame) regulates the size and
number of regions used, by pruning a multiscale segmentation
of video frames. Since regions used for motion compensation
are obtained by segmenting the previously decoded frame, the
shape of the regions need not be transmitted to the decoder.
Furthermore, our hierarchical motion compensation strategy
refines an initial region level, coarse motion field to obtain a
dense motion field which provides pixel level motion vectors. The
refinement procedure does not require any additional information
to be transmitted. This motion compensation technique effectively
addresses the problem of dealing with “holes” and “overlapping
regions” which are inherent to forward motion compensation.
Residual coding is performed using a novel method which exploits
the fact that the energy of the residual resulting from motion
compensation is concentrated in a priori predictable positions.
We will show that this residual coding technique can also be
extrapolated to improve the performance of coders using a block
based motion compensation strategy. A fusion of these concepts
leads to a gain of 2–3 dB in peak signal-to-noise ratio, apart from
significant perceptual improvement, over a generic video coding
algorithm using a block based motion compensation strategy
(such as H.261 or H.263) for a variety of test sequences.
RAR 546 кбайт
|
?
|
| Wenjun Zeng, and Bede Liu, Fellow |
Geometric-Structure-Based Error Concealment with Novel Applications in Block-Based Low-Bit-Rate Coding |
Abstract—This paper first proposes a computationally efficient
spatial directional interpolation scheme, which makes use of
the local geometric information extracted from the surrounding
blocks. The proposed error-concealment scheme produces results
that are superior to those of other approaches, in terms of
both peak signal-to-noise ratio and visual quality. Then a novel
approach that incorporates this directional spatial interpolation
at the receiver is proposed for block-based low-bit-rate coding.
The key observation is that the directional spatial interpolation at
the receiver can reconstruct faithfully a large percentage of the
blocks that are intentionally not sent. A rate-distortion optimal
way to drop the blocks is shown. The new approach can be made
compatible with standard JPEG and MPEG decoders. The blockdropping
approach also has an important application for dynamic
rate shaping in transmitting precompressed videos over channels
of dynamic bandwidth. Experimental results show that the proposed
coding and rate-shaping systems can provide significant
subjective and objective gains over conventional approaches.
RAR 1344 кбайт
|
?
|
| Weixing Zhang and Thomas R. Fischer |
Comparison of Different Image Subband Coding Methods at Low Bit Rates |
Abstract—Two image subband coding methods are introduced
as combinations of trellis-coded quantization (TCQ) with zerotree
and stack-run coding. These TCQ-based image coding algorithms
are compared, at low bit rates, with the set partitioning in
hierarchical trees and stack-run scalar quantization-based image
coding algorithms. Direct use of TCQ with zerotree or stack-run
coding methods is found to provide little or no improvement in
rate-distortion performance compared to scalar quantization.
RAR 495 кбайт
|
?
|
| Nikolaos Doulamis, Anastasios Doulamis, Dimitrios Kalogeras, and Stefanos Kollias |
Low Bit-Rate Coding of Image Sequences Using Adaptive Regions of interest |
Abstract— An adaptive algorithm for extracting foreground
objects from background in videophone or videoconference applications
is presented in this paper. The algorithm uses a neural
network architecture that classifies the video frames in regionsof-
interest (ROI) and non-ROI areas, also being able to automatically
adapt its performance to scene changes. The algorithm
is incorporated in motion-compensated discrete cosine transform
(MC–DCT)-based coding schemes, allocating more bits to ROI
than to non-ROI areas. Simulation results are presented, using the
Claire and Trevor sequences, which show reconstructed images
of better quality, as well as signal-to-noise ratio improvements of
about 1.4 dB, compared to those achieved by standard MC–DCT
encoders.
RAR 356 кбайт
|
?
|
| Dzung T. Hoang, Philip M. Long, and Jeffrey Scott Vitter, Fellow, EEE |
Efficient Cost Measures for Motion Estimation at Low Bit Rates |
Abstract— We present and compare methods for choosing
motion vectors for block-based motion-compensated video coding.
The primary focus is on videophone and videoconferencing
applications, where low bit rates are necessary, where motion
is usually limited, and where the amount of computation is
also limited. In a typical block-based motion-compensated video
coding system, motion vectors are transmitted along with a lossy
encoding of the residuals. As the bit rate decreases, the proportion
required to transmit the motion vectors increases. We provide
experimental evidence that choosing motion vectors explicitly
to minimize rate (including motion vector coding), subject to
implicit constraints on distortion, yields better rate–distortion
tradeoffs than minimizing some measure of prediction error.
RAR 474 кбайт
|
?
|
| Takahiro Fukuhara, Kohtaro Asai, Tokumichi Murakami |
Very Low Bit-Rate Video Coding with Block Partitioning and Adaptive Selection of Two Time-Differential Frame Memories |
Abstract—Recently several studies on very low bit rate video
coding have been reported. One of the major goals of the studies
is to improve coding performance, which gives better subjective
and objective quality than conventional coding methods at the
same bit rate. As the shape and structure of an object in a
picture are arbitrary, the performance of traditional coding with
block-based motion compensation (MC) is not satisfactory. In this
paper, we present advanced MC schemes for very low bit-rate
video coding. Major features of the proposed MC are blockpartitioning
prediction and utilization of two time-differential
reference frames. This coding scheme improves image quality
around objects’ boundaries and consequently reduces prediction
errors. It also works well in the case of object occlusions. The
combination of the proposed MC and discrete cosine transformation
(DCT) will show better performance in several test sequences
than full-spec H.263.
RAR 641 кбайт
|
?
|
| Ralph Neff and Avideh Zakhor |
Very Low Bit-Rate Video Coding Based on Matching Pursuits |
Abstract—We present a video compression algorithm which
performs well on generic sequences at very low bit rates. This
algorithm was the basis for a submission to the November 1995
MPEG-4 subjective tests. The main novelty of the algorithm is a
matching-pursuit based motion residual coder. The method uses
an inner-product search to decompose motion residual signals on
an overcomplete dictionary of separable Gabor functions. This
coding strategy allows residual bits to be concentrated in the areas
where they are needed most, providing detailed reconstructions
without block artifacts. Coding results from the MPEG-4 Class
A compression sequences are presented and compared to H.263.
We demonstrate that the matching pursuit system outperforms
the H.263 standard in both peak signal-to-noise ratio (PSNR)
and visual quality.
RAR 1324 кбайт
|
?
|
| Raj Talluri, Karen Oehler, Thomas Bannon,
Jonathan D. Courtney, Arnab Das, and Judy Liao |
A Robust, Scalable, Object-Based Video Compression Technique for Very Low Bit-Rate Coding |
Abstract—This paper describes an object-based video coding
scheme (OBVC) that was proposed by Texas Instruments to
the emerging ISO MPEG-4 video compression standardization
effort. This technique achieves efficient compression by separating
coherently moving objects from stationary background and
compactly representing their shape, motion, and the content. In
addition to providing improved coding efficiency at very low bit
rates, the technique provides the ability to selectively encode,
decode, and manipulate individual objects in a video stream. This
technique supports all three MPEG-4 functionalities tested in the
November 1995 tests, namely, improved coding efficiency, error
resilience, and content scalability. This paper also describes the
error protection and concealment schemes that enable robust
transmission of compressed video over noisy communication
channels such as analog phone lines and wireless links. The noise
introduced by the communication channel is characterized by
both burst errors and random bit errors. Applications of this
object-based video coding technology include videoconferencing,
video telephony, desktop multimedia, and surveillance video.
RAR 1157 кбайт
|
?
|
