• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.12C
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• pp.1209-1216
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• 2003

The transcoding is needed to modify the bit rate of the video bitstream in accordance with the bandwidth of a variety of channels in order to provide users with a realtime multimedia service and more stable and credible VOD(Video On Demand) service on various wire/wireless network. This paper suggests how to guarantee the video quality in the transcoding process, taking the activity and direction of the macroblock into consideration, thereby reducing the calculation. The threshold of the macroblock's activity and direction is applicable to the different videos, with the DCT coefficients from the intermediate data in the decoding process. Moreover, the suggested video transcoding algorism enables us to maintain the proper video quality and reduce the calculation through the video bit rate change experiment in H.263 environment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.11
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• pp.2465-2473
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• 2012

Recently, as one of low complexity video encoding methods, DVC (Distributed Video Coding) scheme has been actively studied. Most of DVC schemes exploit feedback channel to achieve better coding performances, however, this causes these schemes to have high decoding delay. In order to overcome these, this paper proposes a new fast DVC decoding method using parity-bit request model, which can be obtained by using bit-error rate, sent by encoder with motion vector, which is transmitted through feedback channel by decoder after generating side information. Through several simulations, it is shown that the proposed method improves greatly the decoding speed, compared to the conventional schemes.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.41 no.6
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• pp.91-99
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• 2004

This paper proposed two transcodiing methods, which maintain the same spatio-temporal resolution and reduce a spatial resolution, to convert a H.264 video bitstream into an MPEG-4 video bitstream. When the H.264 video bitstream is transformed into the MPEG-4 video bitstream, the conversions between H.264 block types and MPEG-4 block types are performed by minimizing distortion and the ${\times}4$ block-based motion vector mapping is performed. The proposed two transcoding methods run 4.14～5.1 times as fast as the cascaded transcoding methods in MPEG-4 encoder side, while the PSNR (peak-signal-to ratio) is slightly degrade with maximum 0.3dB.

• The Journal of the Acoustical Society of Korea
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• v.19 no.1
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• pp.97-102
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• 2000

Subband coding is to divide the signal frequency band into a set of uncorrelated frequency bands by filtering and then to encode each of these subbands using a bit allocation rationale matched to the signal energy in that subband. The actual coding of the subband signal can be done using waveform encoding techniques such as PCM, DPCM and vector quantizer(VQ) in order to obtain higher data compression. Most researchers have focused on the error in the quantizer, but not on the overall reconstruction error and its dependence on the filter bank. This paper provides a thorough analysis of subband codecs and further development of optimum filter bank design using vector quantizer. We compute the mean squared reconstruction error(MSE) which depends on N the number of entries in each code book, k the length of each code word, and on the filter bank coefficients. We form this MSE measure in terms of the equivalent quantization model and find the optimum FIR filter coefficients for each channel in the M-band structure for a given bit rate, given filter length, and given input signal correlation model. Specific design examples are worked out for 4-tap filter in 2-band paraunitary filter bank structure. These optimum paraunitary filter coefficients are obtained by using Monte Carlo simulation. We expect that the results of this work could be contributed to study on the optimum design of subband codecs using vector quantizer.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.67-75
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• 2012

Optimal quantizers in conducting the entropy-constrained quantization for high bit rates have the lattice structure. The quantization process is simple due to the regular structure, and various quantization algorithms are proposed depending on the lattice. Such a lattice vector quantizer (VQ) can be implemented by using the sample-adaptive product quantizer (SAPQ) and its output can also be easily entropy encoded. In this paper, the entropy encoding scheme for the lattice VQ is proposed based on SAPQ, and the performance of the proposed lattice VQ, which is based on SAPQ with the entropy coder, is asymptotically compared as the rate increases. It is shown by experiment that the gain for the memoryless Gaussian source also approaches the theoretic gain for the uniform density case.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.3C
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• pp.234-240
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• 2007

In this paper, low complexity block constrained trellis coded quantization (BC-TCQ) structures are introduced, and a predictive BC TCQ encoding method is developed for quantization of line spectrum frequencies (LSF) parameters for narrowband speech coding applications. Trellis-coded quantization(TCQ) is a form of VQ that builds the VQ codebook from interleaved constituent scalar quantization codebooks. The performance is compared to the other VQ, demonstrating reduction in spectral distortion and significant reduction in encoding complexity. The predictive BC-TCQ is about 0.47107 dB superior to the IS-641 split-VQ, 26bits/frame, in spectral distortion sense. The BC-TCQ is 64.54%, 76.93%, 2.35% of the IS-641 split-VQ, respectively, in the complexity of the additions, multiplies, comparisons.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12C
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• pp.1232-1239
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• 2006

In video standards such as MPEG-1/2/4 and H.264/AVC, motion estimation / compensation(ME/MC) process causes the most encoding complexity of video encoder. The full search method, which is used in general video codecs, exhausts much encoding time because it compares current macroblock with those at all positions within search window for searching a matched block. For the alleviation of this problem, the fast search methods such as TSS, NTSS, DS and HEXBS are exploited at first. Thereafter, DS based MVFAST, PMVFAST, MAS and FAME, which utilize temporal or spacial correlation characteristics of motion vectors, are developed. But there remain the problems of image quality degradation and algorithm complexity increase. In this thesis, the proposed algorithm maximizes search speed and minimizes the degradation of image quality by determining initial search point correctly and using simple one-dimension search patterns considering motion characteristics of each frame.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.07a
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• pp.34-36
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• 2012

본 논문에서는 비대칭적 화질을 갖는 스테레오스코픽 영상에서 화질개선을 위해 사용되는 부가정보를 효율적으로 부호화하기위한 방안을 제안한다. 부가정보의 대부분은 좌영상과 우영상의 높은 상관도를 기반으로 하는 양안시차 벡터맵으로 구성되며, 이것을 부호화하기 위해 분포 특성을 분석하였고, 이에 맞는 엔트로피 부호화 방식인 지수 골롬 부호를 적용하였다. 또한, 양안시차 벡터맵의 공간적 데이터의 중복성을 없애기 위해 DPCM을 적용하여 부호화의 효율성을 높였다.

• Journal of Korea Port Economic Association
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• v.27 no.4
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• pp.207-218
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• 2011

This paper investigates the determinants of trade on Southeast Asia via Korean ports using monthly data. I employ Johansen cointegration methodology since the model must be stationary to avoid the spurious results. Johansen(1988) and Johansen and Juselius(1990) propose two statistics for testing the number of cointegrating vectors: the trace and maximum eigenvalue statistics. The null hypothesis that there is no cointegrating vector should be rejected at the 5% level. The results indicate that there is a long-run relationship between trade and variables. This also suggests that these variables have a meaningful equilibrium relationship between trade and variables would not move too far away from each other, displaying a comovement phenomenon for the export and import. Apparently, the error correction term reflects market information in a state of disequilibrium that is bound to be corrected when moving toward the long-run level.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11A
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• pp.1925-1938
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• 2001

In this paper, a new block-matching algorithm for standard video encoder is presented. The slice competition method is proposed as a new scheme, as opposed to a coarse-to-fine approach. The order of calculating the SAD(Sum of Absolute Difference) to fad the best matching block is changed from a raster order to a dispersed one. Based on this scheme, the increasing SAD curve during its calculation is more linear than that of other curves. Then, the candidates of low probability can be removed in the early stage of calculation. And new MV prediction technique with an adaptive search range scheme also assists the proposed block-matching algorithm. As a result, an average of 13% improvement in computational power is recorded by only the proposed MV prediction technique. Synthetically, the computational power is reduced by 3977∼77% than that of the conventional BMAs. The average MAD is always low in various sequences. The results are also very close to the MAD of the full search block-matching algorithm.