1,169 research outputs found
Resilient video coding using difference expansion and histogram modification
Recent advances in multimedia technology have paved the way to the development of several applications, including digital TV broadcasting, mobile TV, mobile gaming and telemedicine. Nonetheless, real time multimedia services still provide challenges as reliable delivery of the content cannot be guaranteed. The video compression standards incorporate error resilient mechanisms to mitigate this effect. However, these methods assume a packet-loss scenario, where corrupted slices are dropped and concealed by the decoder. This paper presents the application of reversible watermarking techniques to facilitate the detection of corrupted macroblocks. A variable checksum is embedded within the coefficient levels and motion vectors, which is then used by the decoder to detect corrupted macroblocks which are concealed. The proposed method employs difference expansion to protect the level values while histogram modification was employed to protect the motion vectors. Unlike previous published work by the same author, this scheme does not need the transmission of side information to aid the recovery of the original level and motion vector values. Simulation results have indicated that significant gains in performance can be achieved over the H.264/AVC standard.peer-reviewe
Robust decoder-based error control strategy for recovery of H.264/AVC video content
Real-time wireless conversational and broadcasting multimedia applications offer particular transmission challenges as reliable content delivery cannot be guaranteed. The undelivered and erroneous content causes significant degradation in quality of experience. The H.264/AVC standard includes several error resilient tools to mitigate this effect on video quality. However, the methods implemented by the standard are based on a packet-loss scenario, where corrupted slices are dropped and the lost information concealed. Partially damaged slices still contain valuable information that can be used to enhance the quality of the recovered video. This study presents a novel error recovery solution that relies on a joint source-channel decoder to recover only feasible slices. A major advantage of this decoder-based strategy is that it grants additional robustness while keeping the same transmission data rate. Simulation results show that the proposed approach manages to completely recover 30.79% of the corrupted slices. This provides frame-by-frame peak signal-to-noise ratio (PSNR) gains of up to 18.1%dB, a result which, to the knowledge of the authors, is superior to all other joint source-channel decoding methods found in literature. Furthermore, this error resilient strategy can be combined with other error resilient tools adopted by the standard to enhance their performance.peer-reviewe
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Research and developments of Dirac video codec
This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel University.In digital video compression, apart from storage, successful transmission of the compressed video
data over the bandwidth limited erroneous channels is another important issue. To enable a video
codec for broadcasting application, it is required to implement the corresponding coding tools (e.g.
error-resilient coding, rate control etc.). They are normally non-normative parts of a video codec and
hence their specifications are not defined in the standard. In Dirac as well, the original codec is
optimized for storage purpose only and so, several non-normative part of the encoding tools are still
required in order to be able to use in other types of application.
Being the "Research and Developments of the Dirac Video Codec" as the research title, phase I of
the project is mainly focused on the error-resilient transmission over a noisy channel. The error-resilient
coding method used here is a simple and low complex coding scheme which provides the
error-resilient transmission of the compressed video bitstream of Dirac video encoder over the packet
erasure wired network. The scheme combines source and channel coding approach where error-resilient
source coding is achieved by data partitioning in the wavelet transformed domain and
channel coding is achieved through the application of either Rate-Compatible Punctured
Convolutional (RCPC) Code or Turbo Code (TC) using un-equal error protection between header plus
MV and data. The scheme is designed mainly for the packet-erasure channel, i.e. targeted for the
Internet broadcasting application.
But, for a bandwidth limited channel, it is still required to limit the amount of bits generated from
the encoder depending on the available bandwidth in addition to the error-resilient coding. So, in the
2nd phase of the project, a rate control algorithm is presented. The algorithm is based upon the Quality
Factor (QF) optimization method where QF of the encoded video is adaptively changing in order to
achieve average bitrate which is constant over each Group of Picture (GOP). A relation between the
bitrate, R and the QF, which is called Rate-QF (R-QF) model is derived in order to estimate the
optimum QF of the current encoding frame for a given target bitrate, R.
In some applications like video conferencing, real-time encoding and decoding with minimum
delay is crucial, but, the ability to do real-time encoding/decoding is largely determined by the
complexity of the encoder/decoder. As we all know that motion estimation process inside the encoder
is the most time consuming stage. So, reducing the complexity of the motion estimation stage will
certainly give one step closer to the real-time application. So, as a partial contribution toward realtime
application, in the final phase of the research, a fast Motion Estimation (ME) strategy is designed
and implemented. It is the combination of modified adaptive search plus semi-hierarchical way of
motion estimation. The same strategy was implemented in both Dirac and H.264 in order to
investigate its performance on different codecs. Together with this fast ME strategy, a method which
is called partial cost function calculation in order to further reduce down the computational load of the
cost function calculation was presented. The calculation is based upon the pre-defined set of patterns
which were chosen in such a way that they have as much maximum coverage as possible over the
whole block.
In summary, this research work has contributed to the error-resilient transmission of compressed
bitstreams of Dirac video encoder over a bandwidth limited error prone channel. In addition to this,
the final phase of the research has partially contributed toward the real-time application of the Dirac
video codec by implementing a fast motion estimation strategy together with partial cost function
calculation idea.BBC R&D and Brunel University
Survey of Error Concealment techniques: Research directions and open issues
© 2015 IEEE. Error Concealment (EC) techniques use either spatial, temporal or a combination of both types of information to recover the data lost in transmitted video. In this paper, existing EC techniques are reviewed, which are divided into three categories, namely Intra-frame EC, Inter-frame EC, and Hybrid EC techniques. We first focus on the EC techniques developed for the H.264/AVC standard. The advantages and disadvantages of these EC techniques are summarized with respect to the features in H.264. Then, the EC algorithms are also analyzed. These EC algorithms have been recently adopted in the newly introduced H.265/HEVC standard. A performance comparison between the classic EC techniques developed for H.264 and H.265 is performed in terms of the average PSNR. Lastly, open issues in the EC domain are addressed for future research consideration
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
Enhance Robustness of Image-in-Image Watermarking through Data Partitioning
Vulnerability of watermarking schemes against intense signal processing
attacks is generally a major concern, particularly when there are techniques to
reproduce an acceptable copy of the original signal with no chance for
detecting the watermark. In this paper, we propose a two-layer, data
partitioning (DP) based, image in image watermarking method in the DCT domain
to improve the watermark detection performance. Truncated singular value
decomposition, binary wavelet decomposition and spatial scalability idea in
H.264/SVC are analyzed and employed as partitioning methods. It is shown that
the proposed scheme outperforms its two recent competitors in terms of both
data payload and robustness to intense attacks.Comment: 5 pages, 7 figures, IEEE TENCON201
An adaptive error resilient scheme for packet-switched H.264 video transmission
2010-2011 > Academic research: refereed > Chapter in an edited book (author)Version of RecordPublishe
HEVC Watermarking Techniques for Authentication and Copyright Applications: Challenges and Opportunities
Recently, High-Efficiency Video Coding (HEVC/H.265) has been chosen to
replace previous video coding standards, such as H.263 and H.264. Despite the
efficiency of HEVC, it still lacks reliable and practical functionalities to
support authentication and copyright applications. In order to provide this
support, several watermarking techniques have been proposed by many researchers
during the last few years. However, those techniques are still suffering from
many issues that need to be considered for future designs. In this paper, a
Systematic Literature Review (SLR) is introduced to identify HEVC challenges
and potential research directions for interested researchers and developers.
The time scope of this SLR covers all research articles published during the
last six years starting from January 2014 up to the end of April 2020.
Forty-two articles have met the criteria of selection out of 343 articles
published in this area during the mentioned time scope. A new classification
has been drawn followed by an identification of the challenges of implementing
HEVC watermarking techniques based on the analysis and discussion of those
chosen articles. Eventually, recommendations for HEVC watermarking techniques
have been listed to help researchers to improve the existing techniques or to
design new efficient ones.Comment: Review article, 20 page
Loss Visibility Optimized Real-time Video Transmission over MIMO Systems
The structured nature of video data motivates introducing video-aware
decisions that make use of this structure for improved video transmission over
wireless networks. In this paper, we introduce an architecture for real-time
video transmission over multiple-input multiple-output (MIMO) wireless
communication systems using loss visibility side information. We quantify the
perceptual importance of a packet through the packet loss visibility and use
the loss visibility distribution to provide a notion of relative packet
importance. To jointly achieve video quality and low latency, we define the
optimization objective function as the throughput weighted by the loss
visibility of each packet, a proxy for the total perceptual value of successful
packets per unit time. We solve the problem of mapping video packets to MIMO
subchannels and adapting per-stream rates to maximize the proposed objective.
We show that the solution enables jointly reaping gains in terms of improved
video quality and lower latency. Optimized packet-stream mapping enables
transmission of more relevant packets over more reliable streams while unequal
modulation opportunistically increases the transmission rate on the stronger
streams to enable low latency delivery of high priority packets. We extend the
solution to capture codebook-based limited feedback and MIMO mode adaptation.
Results show that the composite quality and throughput gains are significant
under full channel state information as well as limited feedback. Tested on
H.264-encoded video sequences, for a 4x4 MIMO with 3 spatial streams, the
proposed architecture achieves 8 dB power reduction for the same video quality
and supports 2.4x higher throughput due to unequal modulation. Furthermore, the
gains are achieved at the expense of few bits of cross-layer overhead rather
than a complex cross-layer design.Comment: Submitted to IEEE Transactions on Circuits and Systems for Video
Technolog
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