• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.3 s.309
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• pp.9-16
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• 2006

Many image and video compression algorithms work by splitting the image into blocks and producing variable-length code bits for each block data. If variable-length code data are transmitted consecutively over error-prone channel without any error protection technique, the receiving decoder cannot decode the stream properly. So the standard image and video compression algorithms insert some redundant information into the stream to provide some protection against channel errors. One of redundancies is resynchronization marker, which enables the decoder to restart the decoding process from a known state in the event of transmission errors, but its usage should be restricted not to consume bandwidth too much. The Error Resilient Entropy Code(EREC) is well blown method which can regain synchronization without any redundant information. It can work with the overall prefix codes, which many image compression methods use. This paper proposes EREREC method to improve FEREC(Fast Error-Resilient Entropy Coding). It first calculates initial searching position according to bit lengths of consecutive blocks. Second, initial offset is decided using statistical distribution of long and short blocks, and initial offset can be adjusted to insure all offset sequence values can be used. The proposed EREREC algorithm can speed up the construction of FEREC slots, and can improve the compressed image quality in the event of transmission errors. The simulation result shows that the quality of transmitted image is enhanced about $0.3{\sim}3.5dB$ compared with the existing FEREC when random channel error happens.

• Journal of Broadcast Engineering
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• v.10 no.3
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• pp.413-421
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• 2005

As the population of HDTV is growing, among many useful features of modern set top boxes (STBs) or digital video recorders (DVRs), video browsing, visual bookmark, and picture-in-picture capabilities are very frequently required. These features typically employ reduced-size versions of video frames, or thumbnail images. Most thumbnail generation approaches generate DC images directly from a compressed video stream. A discrete cosine transform (DCT) coefficient for which the frequency is zero in both dimensions in a compressed block is called a DC coefficient and is simply used to construct a DC image. If a block has been encoded with field DCT, a few AC coefficients are needed to generate the DC image in addition to a DC coefficient. However, the bit length of a codeword coded with variable length coding (VLC) cannot be determined until the previous VLC codeword has been decoded, thus it is required that all codewords should be fully decoded regardless of their necessary for DC image generation. In this paper, we propose a method especially for fast DC image generation from an I-frame using multiple-symbol lookup table (mLUT). The experimental results show that the method using the mLUT improves the performance greatly by reducing LUT count by 50$\%$.

• The KIPS Transactions:PartB
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• v.11B no.6
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• pp.625-632
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• 2004

Since the H.264 encoding adopts both forward prediction and hi-direction prediction modes and exploits Variable Length Coding(VLC), the amount of data generated from video encoder varies as Flaying time goes by. The fixed bit rate encoding system which has limited transmission channel capacity uses a buffer to control output bitstream It's necessary to control the bitstream to maintain within manageable range so as to protect buffer from overflow or underflow. With existing bit amount control algorithms, the $\lambda_{MODE}$ which is relationship between distortion value and quantization parameter often excesses normal value to end up with video error. This paper proposes an algorithm to protect buffer from overflow or underflow by introducing a new quantization parameter against distortion value of H.264 video data. The test results of 6 exemplary data show that the proposed algorithm has the same PSNR as and up to 8% reduced bit rate against existing algorithms.

• The Journal of the Korea Contents Association
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• v.12 no.3
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• pp.77-83
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• 2012

In this paper, a low-complexity embedded compression (EC) Codec algorithm for the wavelet video coder is applied to reduce excessive external memory requirements. The EC algorithm is used to achieve a fixed compression ratio of 50 % under the near-lossless-compression constraint. The EC technique can reduce the 50 % memory requirement for intermediate low-frequency coefficients during multiple discrete wavelet transform stages compared with direct implementation of the wavelet video encoder of this paper. Furthermore, the EC scheme based on a forward adaptive quantization and fixed length coding can save bandwidth and size of buffer between DWT and SPIHT to 50 %. Simulation results show that our EC algorithm present only PSNR degradation of 0.179 and 0.162 dB in average when the target bit-rate of the video coder are 1 and 0.5 bpp, respectively.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.5
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• pp.2101-2121
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• 2020

The rapid growth of instructional videos repositories and their widespread use as a tool to support education have raised the need of studies to assess the quality of those educational resources and their impact on the quality of learning process that depends on them. Khan Academy (KA) repository is one of the prominent educational videos' repositories. It is famous and widely used by different types of learners, students and teachers. To better understand its characteristics and the impact of such repositories on education, we gathered a huge amount of KA data using its API and different web scraping techniques, then we analyzed them. This paper reports the first quantitative and descriptive analysis of Khan Academy repository (KA repository) of open video lessons. First, we described the structure of repository. Then, we demonstrated some analyses highlighting content-based growth and evolution. Those descriptive analyses spotted the main important findings in KA repository. Finally, we focused on users' interactions with video lessons. Those interactions consisted of questions and answers posted on videos. We developed interaction profiles for those videos based on the number of users' interactions. We conducted regression analysis and statistical tests to mine the relation between those profiles and some quality related proposed metrics. The results of analysis showed that all interaction profiles are highly affected by video length and reuse rate in different subjects. We believe that our study demonstrated in this paper provides valuable information in understanding the logic and the learning mechanism inside learning repositories, which can have major impacts on the education field in general, and particularly on the informal learning process and the instructional design process. This study can be considered as one of the first quantitative studies to shed the light on Khan Academy as an open educational resources (OER) repository. The results presented in this paper are crucial in understanding KA videos repository, its characteristics and its impact on education.

• Journal of Broadcast Engineering
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• v.15 no.5
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• pp.642-652
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• 2010

Recently, DVC (Distributed Video Coding) techniques are drawing a lot of interests as one of the future research works to achieve low complexity encoding in various applications. But, due to the limited computational complexity, the performances of DVC algorithms are inferior to those of conventional international standard video coders, which use zig-zag scan, run length code, entropy code and skipped macroblock. In this paper, in order to overcome the performance limit of the DVC system, the distortion for every block is estimated when side information is found at the decoder and then we propose a new selective block encoding scheme which provides the encoder side with the motion information for the highly distorted blocks and then allows the sender to encode the motion compensated frame difference signal. Through computer simulations, it is shown that the coding efficiency of the proposed scheme reaches almost that of the conventional inter-frame coding scheme.

• Journal of Broadcast Engineering
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• v.7 no.4
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• pp.355-361
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• 2002

In this paper, several methods which guarantee the seamless editing when the splicing is applied to the MPEG-2 system streams are described. In the MPEG-2 system standard, it is recommended that the splicing technique is applied in the Transport Stream(TS) domain. However, in view of the video editing, the splicing at an arbitrary picture unit can not be guaranteed. The splicing in the PES domain is only considered in this paper because the PES is one of the MPEG-2 system streams and this result could be directly extended to the video splicing techniques in the TS or PS domain. Thus. the problems that might occur when different two PES streams are spliced and its effects to the video quality are compared and analyzed. Based on this analysis. several methods that can resolve these problems directly in the PES domain are proposed. Consequently, the computer simulation demonstrates that the splicing at a GOP modulo is guaranteed to have good video quality even without considering the state of the PES packet only if the PES_packet_length field of the PES packet header is used.

• Korean Journal of Optics and Photonics
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• v.13 no.6
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• pp.506-509
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• 2002

An optical system for a stereoscopic video recorder is designed with the field of view 42$^{\circ}$ and effective diameter 22 mm. We can use it by attaching it to the front lens of any video camera or camcorder to record a stereoscopic scene. This system is a double Kepler type afocal system to make the image erect and a bi-ocular type to record and display the stereoscopic scene. The optical tube length is folded with several flat mirrors and a beam splitter to be compact. This optical system is composed of 4 groups of lenses and each group serves as a relay lens for minimizing the vignetting effect. Whole field stereoscopic scenes may be captured by perpendicularly polarized alternated recording with a chopper and two perpendicular polarizers, without any loss of light energy. The displayed images may be seen stereoscopically with polarized spectacles and are kinetic because of an afterimage effect.

• Fashion & Textile Research Journal
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• v.26 no.3
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• pp.279-288
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• 2024

Fingernail-related content on YouTube is gaining popularity. This study aimed to present a new direction for nail content marketing and video production by identifying the current status of nail-related content on YouTube and factors affecting views. As for the research method, the study used the YouTube website, and the elements under analysis were classified into YouTuber characteristics (verbal characteristics, age group, gender, professional status, and celebrity status) and content characteristics (nail field, editing elements, and content). The results showed that standard language and terminology were generally used, and the proportion of YouTubers in their 30s was high. All nail-related content creators on YouTube were women, and they were found to be experts who worked as nail artists and nail content creators. As for the content characteristics, the proportion of art videos was high, and the video length was found mostly to be between 10 and 20 minutes. The editing elements included images, videos, and subtitles, and sound effects and background music were used frequently. Finally, it was found that the proportion of videos providing nail tips and know-how, product information, and procedures was high. This study identified factors that influence the number of views for nail videos. As a result, the study was able to present video production ideas for newcomers starting a nail-content YouTube channel, and this will be helpful in the development of nail content.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.11
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• pp.2218-2229
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• 2015

Recently Wi-Fi Alliance defined Wi-Fi direct, which can communicate through a direct connection between the mobile device anytime, anywhere. In Wi-Fi direct, all devices are categorized by group of owner (GO) and client. Since portability is emphasized in Wi-Fi direct devices, it is essential to control the energy consumption of a device very efficiently. In order to avoid unnecessary power consumed by GO, Wi-Fi direct standard defines two power management schemes: Opportunistic power saving scheme and Notice Of Absence (NOA) scheme. But, these two schemes do not consider the traffic pattern, so we cannot expect high energy efficiency. In this paper, we suggest an algorithm to enhance the energy efficiency of Wi-Fi direct power saving, considering the characteristics of multimedia video traffic. Proposed algorithm utilizes the statistical distribution for the size of video frames and adjusts the length of awake interval dynamically. Also, considering the inter-dependency among video frames, the proposed algorithm assigns priorities to video frames and ensures that a video frame with high priority is transmitted with higher probability than other frames with low priority. Simulation results shows that the proposed method outperforms the traditional NOA in terms with average delay and energy efficiency.