• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.1C
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• pp.61-72
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• 2005

For the improvement of coding efficiency, the H.264 standard uses new coding tools such as VBS, 1/4-pel accurate ME, multiple references, intra prediction, loop filter, etc. Using these coding tools, H.264 has achieved significant improvements from rate-distortion point of view compared to existing standards. However, the encoder complexity is greatly increased due to these coding tools. We focus on the complexity reduction method of MB mode selection. Among all modes which can be selected, $8{\times}8$ and intra $4{\times}4$ mode have higher complexity than the others. So we propose the methods for reduction of the $8{\times}8$ and intra $4{\times}4$ mode complexity by using information of other modes with relatively low complexity. Simulation results show that the proposed methods save up to $54.6{\%}$ of total encoding time while keeping the average decrease about 0.012dB in PSNR.

• ETRI Journal
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• v.27 no.5
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• pp.557-562
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• 2005

Low-density parity-check (LDPC) codes have recently emerged due to their excellent performance. However, the parity check (H) matrices of the previous works are not adequate for hardware implementation of encoders or decoders. This paper proposes a hybrid parity check matrix which is efficient in hardware implementation of both decoders and encoders. The hybrid H-matrices are constructed so that both the semi-random technique and the partly parallel structure can be applied to design encoders and decoders. Using the proposed methods, the implementation of encoders can become practical while keeping the hardware complexity of the partly parallel decoder structures. An encoder and a decoder are designed using Verilog-HDL and are synthesized using a $0.35 {\mu}m$ CMOS standard cell library.

• Journal of the Korea Society of Computer and Information
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• v.7 no.2
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• pp.95-100
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• 2002

By feedback channel, the decoder reports the addresses of corrupted macroblocks induced by transmission errors back to the encoder With these negative acknowledgements, the encoder can make the next frame having propagated errors by using forward dependency based on GOBs and MBs of the frame happening transmission errors. The encoder can precisely calculate and track the propagated errors by examining the backward motion dependency for each of four comer pixels in the current encoding frame until before-mentioned the next frame. The error-propagation effects can be terminated completely by INTRA refreshing the affected macroblocks. Such a fast algorithm further reduce the computation and memory requirements. The advantages of the low computation complexity and the low memory requirement are Particularly suitable for real-time implementation.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.1
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• pp.64-70
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• 2011

In an H.264/AVC video encoder, the motion estimation at fractional pixel accuracy improves a coding efficiency and image quality. However, it requires additional computation overheads for fractional search and interpolation, and thus, reducing the computation complexity of fractional search becomes more important. This paper proposes a Pixel Re-composition Fractional Motion Estimation (PRFME) algorithm for an H.264/AVC video encoder. Fractional Motion Estimation performs interpolation for the overlapped pixels which increases the computational complexity. PRFME can reduce the computational complexity by eliminating the overlapped pixel interpolation. Compared with the fast full search, the proposed algorithm can reduce 18.1% of computational complexity, meanwhile, the maximum PSNR degradation is less than 0.067dB. Therefore, the proposed PRFME algorithm is quite suitable for mobile applications requiring low power and complexity.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.1
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• pp.13-20
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• 2004

In this paper, we have analyzed the current MPEG-4 video encoding tools and proposed efcient coding techniques that reduce the complexity of the encoder. Until recently, encoder optimization without shape coding has been a major concern in video for wire/wireless low bit rate coding services. Recently, we found out that the computational complexity of MPEG-4 shape coding plays a very important role in the object-based coding through experiments. We have made an experiment whether we could get optimized object-based coding method through successfully combining latest optimized texture coding techniques with our proposed optimized shape coding techniques. In texture coding, we applied the MVFAST method for motion estimation. We chose not to use IVOPF(Intelligent VOP Formation) but to use TRB(Tightest Rectangular Boundary) for positioning VOP and, finally, to eliminate the spiral search of shape motion estimation to reduce the complexity in shape coding. As a result of experiment, our proposed scheme achieved improved time complexity over the existing reference software by $57.3\%$ and over the optimized method on which only shape coding was applied by $48.7\%$, respectively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.332-335
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• 2007

A real-time frame-layer rate control algorithm with a transmission buffer is proposed for minimizing video quality variation. The proposed rate control method uses a non-iterative optimization method for low computational complexity, and performs bit allocation at the frame level to minimize variation in distortion between frames. In order to reflect the buffer status, we use well-known PID control method. Computational complexity of PID control is very low, so the proposed algorithm is suitable for real-time low-complexity video encoder. Experimental results indicate that the proposed control method provides better PSNR performance than the existing rate control method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.11
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• pp.2009-2014
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• 2007

A novel method of minimizing video quality variation is proposed for a real-time frame-layer rate control algorithm with a transmission buffer. The proposed rate control method uses a non-iterative optimization method for low computational complexity, and performs bit allocation at the frame level to minimize variation in distortion between frames. In order to reflect the buffer status, we use well-known PID control method. Computational complexity of PID control is very low, so the proposed algorithm is suitable for real-time low-complexity video encoder. Experimental results indicate that the proposed control method provides better PSNR performance than the existing rate control method.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.3
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• pp.23-31
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• 2010

The increasing demands on low-power, and low-complexity video encoder have been motivating extensive research activities on distributed video coding (DVC) in which the encoder compresses frames without utilizing inter-frame statistical correlation. In DVC encoder, contrary to the conventional video encoder, an error control code compresses the video frames by representing the frames in the form of syndrome bits. In the meantime, the DVC decoder generates side information which is modeled as a noisy version of the original video frames, and a decoder of the error-control code corrects the errors in the side information with the syndrome bits. The noisy observation, i.e., the side information can be understood as the output of a virtual channel corresponding to the orignal video frames, and the conditional probability of the virtual channel model is assumed to follow a Laplacian distribution. Thus, performance improvement of DVC systems depends on performances of the error-control code and the optimal reconstruction step in the DVC decoder. In turn, the performances of two constituent blocks are directly related to a better estimation of the parameter of the correlation channel. In this paper, we propose an algorithm to estimate the parameter of the correlation channel and also a low-complexity version of the proposed algorithm. In particular, the proposed algorithm minimizes squared-error of the Laplacian probability distribution and the empirical observations. Finally, we show that the conventional algorithm can be improved by adopting a confidential window. The proposed algorithm results in PSNR gain up to 1.8 dB and 1.1 dB on Mother and Foreman video sequences, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.7
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• pp.515-520
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• 2014

In this paper, the protograph-based block low density parity check (LDPC) code, which improves the performance and reduces the encoder/decoder complexity than the conventional Digital Video Broadcasting Satellite Second Generation (DVB-S2) LDPC code used for the marine satellite communication, is proposed. The computer simulation results verify that the proposed protograph-based LDPC code has the better performance in both the bit error rate (BER) and the frame error rate (FER) than the conventional DVB-S2 LDPC code. Furthermore, by analyzing the encoding and decoding computational complexity, we show that the protograph-based block LDPC code has the efficient encoder/decoder structure.

• IEIE Transactions on Smart Processing and Computing
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• v.3 no.6
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• pp.397-403
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• 2014

A new video compression standard called High Efficiency Video Coding (HEVC) has recently been released onto the market. HEVC provides higher coding performance compared to previous standards, but at the cost of a significant increase in encoding complexity, particularly in motion estimation (ME). At the same time, the computing capabilities of Graphics Processing Units (GPUs) have become more powerful. This paper proposes a parallel integer-pel ME (IME) algorithm for HEVC on GPU using the Compute Unified Device Architecture (CUDA). In the proposed IME, concurrent parallel reduction (CPR) is introduced. CPR performs several parallel reduction (PR) operations concurrently to solve two problems in conventional PR; low thread utilization and high thread synchronization latency. The proposed encoder reduces the portion of IME in the encoder to almost zero with a 2.3% increase in bitrate. In terms of IME, the proposed IME is up to 172.6 times faster than the IME in the HEVC reference model.