• The KIPS Transactions:PartB
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• v.13B no.3 s.106
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• pp.197-204
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• 2006

Recent advances in information technology have resulted in rapid growth in the mobile communication. With this explosive growth, reliable transmission and error concealment technique become increasingly important to offer high quality multimedia services. In this paper, we propose an improved BMA(Boundary Matching Algorithm) method using gradient vectors to conceal channel errors in inter-frames of H.264 video images. General BMA method computes the sum of pixel differences of adjacent pixels of the candidate block and its neighbouring blocks, assuming that adjacent pixels have almost the same value. In real images, however, there exist some gradients, which means that the pixel values are increasing or decreasing in a specific direction. In this paper, we develop a precise estimation method of errors in candidates blocks using gradient information and try to recover lost blocks with this technique. Experimental results show the improvement of picture quality about $1{\sim}3dB$ compared to existing methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.9C
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• pp.761-770
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• 2010

In this paper, we propose a new Frame Rate Up-Conversion (FRUC) scheme to increase the frame rate from a lower number into a higher one and enhance the decoded video quality at the decoder. The proposed algorithm utilizes the preliminary frames of forward and backward direction using bilateral prediction. In the process of the preliminary frames, an additional interpolation is performed for the occlusion area because if the calculated value of the block with reference frame if larger than the predetermine thresholdn the block is selected as the occlusion area. In order to interpolate the occlusion area, we perform re-search to obtain the osiomal block considerhe osiomnumber of available ne block consblock. The experimental results show that performance of the proposed algorithm has better PSNR and visual quality than the conventional methods.

• Journal of Broadcast Engineering
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• v.15 no.1
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• pp.52-62
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• 2010

Recently, DVC (Distributed Video Coding) is attracting a lot of research works since this enables us to implement a light-weight video encoder by distributing the high complex tasks such as motion estimation into the decoder side. In order to improve the coding efficiency of the DVC, the existing works have been focused on the efficient generation of side information (SI) or the virtual channel modeling which can describe the statistical channel noise well. But, in order to improve the overall performance, this paper proposes a new scheme that can be implemented with simple bit operations without introducing complex operation. That is, the performance of the proposed scheme is enhanced by using the fact that the Wyner-Ziv (WZ) frame and side information are highly correlated, and by reducing the effect of virtual channel noise which tends to be clustered in some regions. For this aim, this paper proposes an efficient pixel-domain WZ (PDWZ) CODEC which effectively exploits the statistical redundancy by using the code conversion and Gray code, and then reduces the channel noise by using the bit interleaver. Through computer simulations, it is shown that the proposed scheme can improve the performance up to 0.5 dB in objective visual quality.

• Journal of IKEEE
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• v.16 no.1
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• pp.7-14
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• 2012

In this paper, a reception rate of terrestrial digital TV broadcasting service is analyzed and a novel method which can estimate the broadcasting coverage rate more objectively and reliably than the existing method is proposed. Previous method measures the reception rate by means of electric field intensity measurement or subjective video quality assessment. Because of limited measuring points, it inherently has measurement error and cannot consider the viewer's receiving conditions in real-time. In order to consider the viewer's population and receiving environment, morphology which characterizes the viewer's receiving environment is extracted using household census data of National Statistical Office and the land cover map of Ministry of Environment. Using the extracted geographical morphology, the reception rate of terrestrial digital TV broadcasting service is calculated with Spectrum Management Intelligence System (SMIs). Proposed method can calculate the reception rate more objectively and reliably than the existing methods because it fully considers the viewer's receiving environments in real-time.

• Journal of Broadcast Engineering
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• v.10 no.4 s.29
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• pp.621-631
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• 2005

To enhance the performance of multi-view sequence CODEC, an efficient disparity vector coding method fur multiview sequences is proposed herein. For higher coding efficiency, we encode the differential vectors acquired by subtracting the original vectors from the predicted ones. To enhance the performance of disparity vector coding, it is essential to predict the disparity vectors accurately. The prediction by this proposed method utilizes the correlation among the multiview images, while conventional methods exploit the correlation among the causal blocks. Experiments were performed fur three different 5 view sequences. We were able to confirm that the proposed method predicts disparity vectors accurately by comparing the entropy and the mean absolute values for differential vectors with conventional methods. Its performance is superior to vector coding methods used in MPEG-4 which uses only a spatial correlation. The proposed method increases the coding efficiency by a factor of $30{\~}45\%$ while preserving image quality.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.9
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• pp.2091-2098
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• 2010

This paper proposes a hologram data compression scheme that uses the existing image/video compression techniques, in which the existing techniques are modified appropriately to fit to the characteristics of hologram. In this paper we use CGH as the hologram data. The proposed scheme uses the generation characteristics of a CGH to consist of a pre-processing, spatial segmentation of a CGH, frequency-transformation with 2D-DCT (2-dimensional discrete cosine transform), and motion estimation and residual image generation in the frequency-domain. It uses H.264/AVC, the lossless compressor BinHex, and a linear quantizer that we have made. From the experiments the proposed scheme showed the image quality of about 25.4 dB at the compression ratio of 10:1 and about 16.5dB at 90:1 compression ratio.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.5C
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• pp.503-511
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• 2006

H.264 adopts new coding tools such as intra-prediction, loop filter, etc. The adoption of these tools enables an H.264-coded bitstream to have more information compared with previous standards. In this paper we proposed an effective spatial error concealment method for H.264. Among the information included in an H.264-coded bitstream, we use intra-mode for recovering a damaged block. This is because prediction direction in intra-mode is highly correlated to the edge direction of a lost macroblock. We first estimate the edge direction using intra-modes of blocks adjacent to a lost macroblock, and classify the area in a damaged macroblock into the edge and the flat area. And then our method recovers pixel values in the edge area using edge-directed interpolation, and recovers pixel values in the flat area using weighted interpolation. Simulation results show the proposed method yields better video quality than conventional approaches by 0.35 to 5.48 dB.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.5
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• pp.187-195
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• 2005

A new segmentation-based image coding method which no needs transmission of contour data is proposed. The shape information acts as bottleneck in the segmentation-based video coding because it has much portion of transmission data. The proposed method segments a previous decoded frame, instead of a current frame. As a result, there is no need for transmission of contour information to a decoder. Therefore, the saved bits can be assigned to encode other information such as error signals. As shown in experiment results, if data rate is very highly increased due to abrupt motion under very low bit rate coding having limited transmission bits, PSNR of conventional block-based method go down about 20dB, while the proposed method shows a good reconstruction quality without rapid PSNR drop.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.49 no.2
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• pp.69-75
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• 2012

This paper presents a novel de-interlacing algorithm that can make up motion compensation errors by using maximum a posteriori (MAP) estimator. First, a proper registration is performed between a current field and its adjacent fields, and the progressive frame corresponding to the current field is found via MAP estimator based on the computed registration information. Here, in order to obtain a stable solution, well-known bilateral total variation (BTV)-based regularization is employed. Next, so-called feathering artifacts are detected on a block basis effectively. So, edge-directional interpolation is applied to the pixels where feathering artifact may happen, instead of the above-mentioned temporal de-interlacing. Experimental results show that the PSNR of the proposed algorithm is on average 4dB higher than that of previous studies and provides the better subjective quality than the previous works.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.6
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• pp.68-77
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• 2009

A single field deinterlacing method, namely interpolation algorithm derived from low resolution (ILR), is presented in this paper. Traditional deinterlacing methods usually employ edge-based interpolation technique within pixel-based estimation. However, edge-based methods are somehow sensitive to noise and intensity variation in the image. Moreover, the methods are not satisfied in deciding the exact edge direction which controls the performance of the interpolation. In order to reduce the sensitivity, the proposed algorithm investigates low-resolution characteristics of the pixel to be interpolated, and applies it to high-resolution image. Simulation results demonstrates that the proposed method gives not only a better objective performance in terms of PSNR results compare to conventional edge-based interpolation methods, but also better subjective image quality.