ERROR-RESILIENT H.264/AVC VIDEO TRANSMISSION USING TWO-WAY DECODABLE VARIABLE LENGTH DATA BLOCK
Abstract—Standard video coders utilize variable length coding
(VLC) to obtain more data compression in addition to what lossy
coding has achieved at the expense of making the compressed
bitstream very vulnerable to channel errors. Even a 1-bit error
incurred in the bitstream may cause the follow-up bitstream
to be either erroneously decoded or completely undecodable,
and this could further result in error propagation. To mitigate
this phenomenon, a new VLC coding scheme is proposed in
this paper, called the two-way decodable variable length data
block (TDVLDB), which allows the compressed bitstream to
be bidirectionally decodable without exploiting data partitioning.
The proposed TDVLDB scheme is able to effectively recover more
uncorrupted data from the corrupted packets. Furthermore, it is
able to correct some, if not all, channel errors of a finite-length
burst error. To effectively identify the location of the first actual
error incurred within the current slice, a bitstream similarity measurement
(BSM) algorithm is proposed. Note that the proposed
TDVLDB scheme is generic in the sense that it can be exploited
in any image or video coding framework as long as it involves the
use of VLC and requires error-resilience capability. In this paper,
the proposed TDVLDB is incorporated into the H.264/advanced
video coding (AVC) coder to evaluate its error-resilience performance
in terms of rate-distortion coding efficiency. Compared
with the baseline H.264/AVC coding, the TDVLDB-incorporated
H.264/AVC-based coding scheme has demonstrated significant
objective and subjective video quality improvements when the
bitstream is transmitted over error-prone channels.
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FREQUENCY COMPOUNDING FOR ULTRASOUND FREEHAND ELASTOGRAPHY
Abstract— Ultrasound elastography is the technique of obtaining
the tissue relative stiffness information, which plays an important
role in early diagnosis. Conventional elastography computes the
strain from the gradient of the displacement estimates between
gated pre- and post-compression echo signals. Although
elastography has been proven to be a potential diagnosis tool for
breast/prostate tumor, vascular stiffening and hepatocirrhosis
diseases, the application of frequency compounding in
elastography to reduce coherent artifact of elastic imaging has
rarely been reported. In this paper, a new method called
Transmit-side Frequency Compounding for Elastography (TSEC)
is proposed, which involves using weighted compounding of
different frequency sub-elastograms. The sub-elastograms are
formed from the corresponding probe center frequency echo
signal pairs reflected from the tissue ROI. Due to the frequency
dependent reflection process, these sub-elastograms should have
different speckle pattern. Upon compounding these subelastograms,
the amount of speckle in the resultant strain image
is reduced. The effect of TSFC are investigated through phantom
experiments, which confirms the reduction in strain image
artifact is accomplished with no sacrifice of real-time ultrasonic
imaging as well as a measurable improvement in SNRe and CNRe.
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