• Journal of Korea Multimedia Society
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• v.17 no.12
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• pp.1402-1411
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• 2014

Buyer-seller watermarking protocol is defined as the practice of imperceptible altering a digital content to embed a message using watermarking in the encryption domain. This protocol is acknowledged as one kind of copyright protection techniques in electronic commerce. Buyer-seller watermarking protocol is fundamentally based on public-key cryptosystem that is operating using the algebraic property of an integer. However, in general usage, digital contents which are handled in watermarking scheme mostly exist as real numbers in frequency domain through DCT, DFT, DWT, etc. Therefore, in order to use the watermarking scheme in a cryptographic protocol, digital contents that exist as real number must be transformed into integer type through preprocessing beforehand. In this paper, we presented a new watermarking scheme in an encrypted domain in an image that is based on the block-DCT framework and homomorphic encryption method for buyer-seller watermarking protocol. We applied integral-processing in order to modify the decimal layer. And we designed a direction-adaptive watermarking scheme by analyzing distribution property of the frequency coefficients in a block using JND threshold. From the experimental results, the proposed scheme was confirmed to have a good robustness and invisibility.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.4
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• pp.106-114
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• 2016

In this paper, we propose an efficient integer inverse transform structure for vp9 decoder. The proposed structure is a hardware structure which is easy to control and requires less hardware resources, and shares algorithms for realizing entire DCT(Discrete Cosine Transform), ADST(Asymmetric Discrete Sine Transform) and WHT(Walsh-Hadamard Transform) in vp9. The integer inverse transform for vp9 google model has a fast structure, named butterfly structure. The integer inverse transform for google C model, unlike universal fast structure, takes a constant rounding shift operator on each stage and includes an asymmetrical sine transform structure. Thus, the proposed structure approximates matrix coefficient values for all transform mode and is used to matrix operation method. With the proposed structure, shared operations for all inverse transform algorithm modes can be possible with reduced number of multipliers compared to the butterfly structure, which in turn manages the hardware resources more efficiently.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.11
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• pp.1477-1485
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• 2021

Recently, super-resolution has been intensively studied only on upscaling models with integer magnification. However, the need to expand arbitrary magnification is emerging in representative application fields of actual super-resolution, such as object recognition and display image quality improvement. In this paper, we propose a model that can support arbitrary magnification by using the weights of the existing integer magnification model. This model converts super-resolution results into the DCT spectral domain to expand the space for arbitrary magnification. To reduce the loss of high-frequency information in the image caused by the expansion by the DCT spectral domain, we propose a high-frequency attention network for arbitrary magnification so that this model can properly restore high-frequency spectral information. To recover high-frequency information properly, the proposed network utilizes channel attention layers. This layer can learn correlations between RGB channels, and it can deepen the model through residual structures.

• JSTS:Journal of Semiconductor Technology and Science
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• v.7 no.4
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• pp.247-253
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• 2007

In this paper, a high throughput multiple transform architecture for H.264 Fidelity Range Extensions (FRExt) is proposed. New techniques are adopted which (1) regularize the $8{\times}8$ integer forward and inverse DCT transform matrices, (2) divide them into four $4{\times}4$ sub-matrices so that simple fast butterfly algorithm can be used, (3) because of the similarity of the sub-matrices, mixed butterflies are proposed that all the sub-matrices of $8{\times}8$ and matrices of $4{\times}4$ forward DCT (FDCT), inverse DCT (IDCT) and Hadamard transform can be merged together. Based on these techniques, a hardware architecture is realized which can achieve throughput of 1.488Gpixel/s when processing either $4{\times}4\;or\;8{\times}8$ transform. With such high throughput, the design can satisfy the critical requirement of the real-time multi-transform processing of High Definition (HD) applications such as High Definition DVD (HD-DVD) ($1920{\times}1080@60Hz$) in H.264/AVC FRExt. This work has been synthesized using Rohm 0.18um library. The design can work on a frequency of 93MHz and throughput of 1.488Gpixel/s with a cost of 56440 gates.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9C
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• pp.697-703
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• 2008

The H.264/AVC video coding standard provides higher coding efnciency compared to the conventional MPEG-2 standard. Since a lot of videos have been encoded using MPEG-2, the format conversion from MPEG-2 to H.264 is essential. In this paper, we propose an efficient method for the conversion of DCT coefficients to H.264/AVC transform coefficients. This conversion is essential, since $8{\times}8$ DCT and $4{\times}4$ integer transform are used in MPEG-2 and H.264/AVC, respectively. The mathematical analysis and computer simulation show that the computational complexity of the proposed algorithm is reduced compared to the conventional algorithm, while the loss caused by the conversion is negligible.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.145-147
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• 2006

Image resizing is to change an image size by upsampling or downsampling of a digital image. Most still images and video frames are given in a compressed domain on digital media. Image resizing of a compressed image can be performed in a spatial domain via decompression or recompression. In general, resizing of a compressed image in a compressed domain is much faster than that in a spatial domain. In this paper, we propose an approach to resize images in the integer discrete cosine transform (DCT) domain, which exploits the multiplication-convolution property of DCT.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.9
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• pp.4448-4466
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• 2018

In recent years, due to its high efficiency and better performance, the high efficiency video coding (HEVC) has become the most common compression standard in the field of video coding. In this paper, the framework of HEVC is deeply analyzed, and an improved HEVC video coding algorithm based on all phase biorthogonal transform (APBT) is proposed, where APBT is utilized to replace the discrete cosine transform (DCT) and discrete sine transform (DST) in original HEVC standard. Based on the relationship between APBT and DCT, the integer APBT is deduced. To further improve the coding performance, an optimal HEVC video coding algorithm based on hybrid APBT is proposed. The coding performance of the proposed HEVC coding algorithm is improved without increasing the complexity. Experimental results show that compared with HEVC standard algorithm, the improved HEVC video coding algorithm based on hybrid APBT can improve the coding performance of chrominance components by about 0.3%.

• 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 Broadcast Engineering
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• v.15 no.3
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• pp.434-453
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• 2010

In this paper, we propose 3DTE(3-Dimensional Transform Environment) that is based on 3DT(Dimensional Transform) that performs 2-dimensional integer DCT(Discrete Cosine Transform) based on $4{\times}4$ block and 1-dimensional integer DCT based on $4{\times}1$ block after collecting same frequency coefficients in neighboring $4{\times}4$ block and supports it's additional coding tools for high performance. The transform of 3DT can keep prediction error by using $4{\times}4$ block and reduce spatial redundancy additionally. The proposed 3DTE can provide coding tools to improve the coding efficiency with using 3DT. The performance of 3DTE compared to JM11.0 is average 3.58% and 5.40% bit savings for all test sequences and HD sequences, respectively, with keeping subjective video quality in High profile.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.1
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• pp.23-32
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• 2011

In this paper, we develop a method for generating thumbnail images at hybrid domain combined the spatial domain and transform domain. The proposed method generates a pixel of a thumbnail image by adding a DC value of residual transform coefficients and an average value of an estimate block. For effectively calculating average values of estimate blocks, we propose a method for reconstructing the boundary pixels of a block. In comparison to the conventional method of decoding the bit stream then scaling down the decoded images, the developed method reduces the complexity by more than 60% while producing identical thumbnail images.