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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