• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.1
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• pp.129-136
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• 2004

In this paper, we proposed quad variable rates ADPCM coding method for efficient speech transmission and real time porcessing is implemented on TMS320C6711-DSP. The modified ADPCM with four variable coding rates, 16[kbps], 24[kbps], 32[kbps] and 40[kbps] are used for speech window samples for good quality speech transmission at a small data bits and real time encoding and decoding is implemented using DSP. ZCR is used to identify the influence of the noise on the speech signal and to decide the rate change threshold. For noise superior signals, low coding rates are applied to minimize data bit and for noise inferior signals, high coding rates are applied to enhance the speech quality. In most speech telecommunications, silent period takes more than half of the signals, speech quality close to 40[kbps] can be obtained at comparabley low data bits and this is shown by simulation and experiments. TMS320C6711-DSK board has 128K flash memory and performance of 1333MIPS and has meets the requirements for real time implementation of proposed coding algorithm.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.11a
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• pp.172-173
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• 2013

최근 표준화가 완료된 HEVO(High Efficiency Video Coding)에서는 계층적 구조를 갖는 가변블록의 크기를 사용하고 재귀적으로 부호화를 수행사여, 최적의 부호화단위(CU: Coding Unit) 분할 구조와 예측단위(PU: Prediction Unit)를 결정함으로써 높은 부호화 효율을 얻을 수 있는 반면 부호화 복잡도가 증가하는 문제가 있다. 본 논문에서는 부호화기의 복잡도를 감소시키기 위한 고속 부호화 알고리즘으로 고속 모드 결정 기법을 제안한다. 제안기법은 상위 깊이(CU: Coding Unit)의 최적 모드와 부호화 율-왜곡 비용을 이용해서 현재 깊이 CU에서의 특정 모드의 율-왜곡 비용 계산을 생략함으로써 PU 탐색을 조기 종료한다. 즉, 상위 깊이 CU의 조건에 따라 화면간 예측 모드의 일부 또는 화면내 예측을 수행하지 않는다. 실험결과 제안기법은 HM 12.0대비 0.2%의 비트 증가에 22.9%의 계산시간 감소 효과를 얻을 수 있음을 확인하였다.

• Journal of Digital Convergence
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• v.14 no.10
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• pp.261-269
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• 2016

This paper aims to propose a novel technology of network convergence to provide ultra high speed internet services over CATV networks, by which a CMC(cable modem concentrator) and CM(cable modem) of 1Gbps level are designed. This technology not only lowers the production cost in comparison to the existing bonding technology with DOCSIS specification but also enables the adjustment of data speed based on the channel bandwidth. According to the experiments, when convolutional code rate with 128QAM is changed to 1/2, 2/3, 3/4 and 7/8, the data recorded the maximum transmission speed of up to 299 Mbps at the zero error rate. As the convolutional code rates with 256QAM is increased, it showed 334Mbps at the error rate of $10^{-5}$. Based on the findings of this paper, if we secure the channel bandwidth of 200MHz and adjust the modulation order of QAM and the convolution code rate depending on the channel status, we can get the transmission speed of more than 1Gbps, which is much more competitive in its function and price than the existing technology based on DOCSIS.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.348-351
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• 2011

가변적인 블록을 이용하는 H.264/AVC 인터 화면에서의 모드 결정 방법은 $16{\times}16$부터 $P8{\times}8$ 모드까지 인터 모드에 대해 비트율 왜곡값을 계산 한 뒤 공간적 상관도를 고려하기 위해 인트라 $4{\times}4$와 인트라 $16{\times}16$ 모드까지 비트율 왜곡값을 계산하고, 계산된 비트율 왜곡값 중 가장 작은 값을 갖는 모드를 최종 모드로 선택한다. 하지만 이러한 과정으로 부호기의 복잡도는 증가한다. 복잡도를 감소시키기 위해 본 논문에서는 IPPP구조에서의 인터 모드와 인트라 모드의 특징을 이용하여 고속 부호화를 제안한다. 제안하는 알고리즘은 인터 모드에 대해서 최적 모드를 결정하기 위한 비트율 왜곡값의 상관도와 시간 상관도를 이용하고, 인트라 모드에 대해서는 인트라 화면 내에서의 각 인트라 모드에 대한 최대 최소 임계값을 이용하여, 발생확률이 낮은 인터와 인트라 모드의 활성화 여부를 결정한다. 본 알고리즘의 적용 범위는 상대적으로 인터 화면에서 발생 빈도가 낮은 $16{\times}8$, $8{\times}16$, $P8{\times}8$와, 인트라 $4{\times}4$, 인트라 $16{\times}16$ 모드이다. 제안하는 알고리즘은 기존의 H.264/AVC에 비해 1.36% 비트가 증가 했고, PSNR은 0.06dB 감소했다. 즉, 부호화 효율의 큰 감소 없이 평균 42.58%의 부호화 시간을 감소시켰다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.40 no.5
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• pp.417-425
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• 2003

H.264, which is the latest video coding standard of both ITU-T(International Telecommunication Union-Telecommunication standardization sector) and MPEG(Moving Picture Experts Group), adopts new video coding tools such as variable block size motion estimation, multiple reference frames, quarter-pel motion estimation/compensation(ME/MC), 4${\times}$4 Integer DCT(Discrete Cosine Transform), and Rate-Distortion Optimization, etc. These new video coding tools provide good coding of efficiency compared with existing video coding standards as H.263, MPEG-4, etc. However, these new coding tools require the increase of encoder complexity. Therefore, in order to apply H.264 to many real applications, fast algorithms are required for H.264 coding tools. In this paper, when encoder MacroBlock(MB) mode is decided by rate-distortion optimization tool, fast mode decision algorithm by skipping variable block size ME/MC and spatial-predictive coding, which occupies most encoder complexity, is proposed. In terms of computational complexity, the proposed method runs about 4 times as far as JM(Joint Model) 42 encoder of H.264, while the PSNR(peak signal-to-noise ratio)s of the decoded images are maintained.

• Journal of the Korea Computer Industry Society
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• v.6 no.5
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• pp.801-812
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• 2005

H.264/AVC is the international video coding standard which has significant improvements of coding efficiency. ITU-T(International Telecommunication Union-Telecommunication standardization sector) and MPEG(Moving Picture Experts Group) adopts various complex coding tool such as variable block size motion, multiple reference frames, quarter-pel motion estimation/compensation (ME/MC) and rate-distortion(RD) optimization, etc. H.264 reference model employs complex mode decision technique based on RD optimization which requires high computational complexity. In this paper, we propose an efficient coding mode decision based on the cost distribution of RD in the macroblock coding mode sequence. Simulation results show that the proposed method reduces encoding time by 34% on average and save the number of computing RD cost by 82%.

• Journal of Broadcast Engineering
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• v.4 no.2
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• pp.127-133
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• 1999

The conventional fractal image compression based on discrete wavelet transform uses the fixed block size in fractal coding and reduces PSNR at low bit rate. This paper proposes a fractal image coding based on discrete wavelet transform which improves PSNR by using variable block size in fractal coding. In the proposed method. the absolute values of discrete wavelet transform coefficients are computed. and the discrete wavelet transform coefficients of different highpass subbands corresponding to the same spatial block are assembled. and the fractal code for the range block of each range block level is assigned. and then a decision tree C. the set of choices among fractal coding. "0" encoding. and scalar quantization is generated and a set of scalar quantizers q is chosen. And then the wavelet coefficients. fractal codes. and the choice items in the decision tree are entropy coded by using an adaptive arithmetic coder. This proposed method improved PSNR at low bit rate and could achieve a blockless reconstructed image. As the results of experiment. the proposed method obtained better PSNR and higher compression ratio than the conventional fractal coding method and wavelet transform coding.rm coding.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.105-108
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• 2004

음성 부호화 기술은 전송률과 복잡도를 줄이고 음질을 향상시키는 방향으로 진행되고 있다. 현재 상용화되고 있는 CELP형 보코더는 낮은 전송률에 비해 우수한 음질을 제공한다. 본 논문에서는 기존의 방식과 다르게 보코더 단에 입력 음성이 들어가기 앞서 전처리 기법을 수행하는 전처리단을 부가하여 전송률을 낮추는 방법을 소개하고, 소개된 방법들을 각기 비교하고 분석하고자 한다. 전처리기법들을 음성 인식이나 합성에서 사용되는 파라미터들을 적용시켰으며, 처리시간이나 계산시간에 있어 기존의 방식에서 많은 영향을 미치지 않은 간단한 알고리즘으로 구현하였다. 소개하는 전처리단에서는 기존의 코딩방식에서 사용하지 않은 파라미터들, 발성율, 지속시간, PSOLA 방식들을 이용하였다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.12
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• pp.1750-1754
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• 2013

A variable bit rate speech coder is presented. The coder is based on the observation that a speech signal can be viewed as a combination of piecewise linear signals in a short time period. The encoder detects the sample points where the slope of the signal changes, which are called the inflection points in this paper. The coder transmits the location and value for the detected inflection sample, but only the location information for the noninflection samples. In the decoder, the noninflection samples are estimated with interpolation of the received information. Several factors affecting the performance of the coder have been tested through simulation. Simulation results show that the linear interpolation produces 1 ~ 5 dB improvement over the cubic spline interpolation. And the -law companding does not provide any benefit when it is applied before the inflection detection. With low threshold values in the inflection point detection, the coder shows better MOS and more than 16 dB improvement in SNR compared to the continuously variable slope delta modulation (CVSDM).

• Journal of Broadcast Engineering
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• v.13 no.5
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• pp.732-743
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• 2008

In H.264/AVC, 4$\times$4 block transform is used for intra and inter prediction instead of 8$\times$8 block transform. Using small block size coding, H.264/AVC obtains high temporal prediction efficiency, however, it has limitation in utilizing spatial redundancy. Motivated on these points, we propose a multi-dimensional transform which achieves both the accuracy of temporal prediction as well as effective use of spatial redundancy. From preliminary experiments, the proposed multi-dimensional transform achieves higher energy compaction than 2-D DCT used in H.264. We designed an integer-based transform and quantization coder for multi-dimensional coder. Moreover, several additional methods for multi-dimensional coder are proposed, which are cube forming, scan order, mode decision and updating parameters. The Context-based Adaptive Variable-Length Coding (CAVLC) used in H.264 was employed for the entropy coder. Simulation results show that the performance of the multi-dimensional codec appears similar to that of H.264 in lower bit rates although the rate-distortion curves of the multi-dimensional DCT measured by entropy and the number of non-zero coefficients show remarkably higher performance than those of H.264/AVC. This implies that more efficient entropy coder optimized to the statistics of multi-dimensional DCT coefficients and rate-distortion operation are needed to take full advantage of the multi-dimensional DCT. There remains many issues and future works about multi-dimensional coder to improve coding efficiency over H.264/AVC.