• Journal of Korea Multimedia Society
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• v.15 no.9
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• pp.1086-1092
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• 2012

In this paper, we propose the rate control scheme reducing frame skipping at low bit-rate. As the method considering lossy parts in the compressing process at the existing scheme, the proposed scheme is improved by subtracting the converted bits from the target bit-rate of the current frame. The converted bits are the value resulted from multiplying the ratio of the current frame MAD to the previous frame MAD by the compressed bits changed from the remaining values after compressing the previous frame.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.11a
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• pp.270-273
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• 2010

스케일러블 비디오 부호화(SVC: Scalable Video Coding)는 하나의 비트스트림 결과물로부터 둘 이상의 다중 비트율 및 해상도, 프레임율을 추출할 수 있도록 MPEG의 스케일러블 비디오 코딩 국제 표준을 준수하여 부호화한 비디오 비트스트림을 의미한다. 우리는 SVC(Scalable Video Coding)기반기술을 이용하여 하나의 콘텐츠를 통해 소비환경에 적응적인 비디오 스트리밍 서비스를 IP망을 기반으로 적용하기 위한 응용기술을 개발하고 있다. 본 논문에서는 단말로 부터 전송채널에 대한 상태를 전송받아 이에 맞게 콘텐츠를 적응변환 하고 다양한 품질의 단말에서의 스트리밍을 제공하는 SVC 미디어 서버를 관리하는 SVC 서버 관리 제어기의 설계 및 그 구현에 관한 내용이다. 이와 같이 SVC 서버 관리 제어기의 개발을 통해서 SVC의 다양한 콘텐츠 적응레벨을 설정하고 관리할 수 있다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.12
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• pp.2315-2320
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• 2006

A real-time frame-layer rate control algorithm with a token bucket traffic shaper is proposed for low bit rate video coding. 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 the average distortion over an entire sequence as well as variations in distortion between frames. In order to reduce the quality fluctuation, we use a sliding window scheme which does not require the pre-analysis process. Therefore, the proposed algorithm does not produce time delay from encoding, and is suitable for real-time low-complexity video encoder. Experimental results indicate that the proposed control method provides better visual and PSNR performances than the existing rate control method.

• Journal of Broadcast Engineering
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• v.9 no.2
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• pp.142-150
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• 2004

MPEG-4 AVC is an international video coding standard that is being developed. The standardization is mainly targeted at a very high compression ratio. MPEG-4 AVC is a general video coding technology that may be used in various applications. Therefore, MPEG-4 AVC needs an efficient rate control method to be applied in various communication environments. This paper is based on the rate control method that considers human visual characteristic. In this paper, we propose the constant bit rate control method using adaptive quantization and scene change detection. Experiments performed using various test images and experimentation results exhibits a favorable performance over existing rate control methods.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2004.04a
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• pp.555-558
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• 2004

최근 인터넷의 발전으로 디지털 오디오 및 비디오와 같은 멀티미디어 스트림에 대한 요구가 증가하고 있다. 이러한 멀티미디어 스트리밍을 UDP로 전송할 경우 TCP와 같은 혼잡제어를 수행하지 않기 때문에 동일한 전송경로의 TCP 트래픽 궁핍을 일으켜 혼잡붕괴 및 막대한 전송지연을 초래한다. 이러한 문제점으로 인하여 실시간 멀티미디어 스트림의 전송지연과 혼잡제어를 위한 새로운 전송기법과 프로토콜에 대한 다각적인 연구가 수행되고 있다. TCP 친화적 혼잡제어 기법은 크게 일반적인 혼잡윈도우 관리기능을 이용하는 윈도우 기반 혼잡제어와 TCP 모델링 방정식 둥을 이용하여 전송율을 직접 조절하는 율 기반 혼잡제어로 나눌 수 있다. 본 논문은 윈도우 기반과 율 기반을 복합적으로 다룬 하이브리드형 TCP-friendly 혼잡제어 기법에서 Square-root 혼잡회피 알고리즘을 제안하였으며, NS를 사용하여 제안한 TEAR의 성능을 실험하였다. 실험을 통하여 제안한 기법의 적용으로 TEAR의 안정성을 개선함을 알 수 있었다.

• The Transactions of the Korea Information Processing Society
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• v.6 no.2
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• pp.534-542
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• 1999

A sell-designed rate control strategy can improve overall picture quality for video transmission over a constant bit rate channel and the rate control method is not a normative part of MPEG-video standard, the performance of MPEG video codec can be quite different depends on how to implement the rate control scheme. The rate control scheme proposed in MPEG show good results when scene changes is not occurred. But it has weakness that it does not properly handle scene-changed pictures. Therefore picture quality after scene change is deteriorated, and possibility of overflow occurrence becomes high. In this paper, a new method for detection of scene change occurrence using local variance and a new determination scheme for adaptive quantization parameter, mqunt, which can consider local characteristic of an image by using previously computed the local variance from the scene change detection part are proposed. IN addition, and adaptive rate control scheme which can handles scene changed picture very efficiently by scene-changed picture is proposed. Computer simulations are performed to verify the performance of the proposed algorithm. The suggested detection algorithm precisely detected scene change. And the proposed rate control scheme shows better rate control performance as compared with that of the conventional MPEG scheme.

• Journal of Advanced Navigation Technology
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• v.13 no.4
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• pp.523-531
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• 2009

In this study, we propose a joint source/channel rate control algorithm for video encoder targeting packet erasure channel. Based on the buffer constraints of video communication systems, encoding rate constraint is presented. After defining source distortion models for coded and skipped video frames and a channel distortion model for packet errors and their propagation, an average distortion model of received video is proposed for a given encoding window. Finally, we define an optimization problem to minimize the average distortion for given channel rates and packet loss rates by controlling spatio-temporal parameters of source video and FEC block sizes. Then, we propose a window-based algorithm to solve the problem in real-time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.8
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• pp.2010-2024
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• 1998

In video coding, it is important to improve the average picture quality as well as to maintain cosistent picture quality between consecutive pictures. In this paper, we propose a distortion-rate estimation method for MPEG-2 video and a forward rate control method, using the proposed estimation result, to be able to obtain the improved and consistent picture quality of CBR (Constant Bit Rate) encoded MPEG-2 video. The proposed distortion-rate estimation enable us to predict the distortion and the bits generated from an encoded picture at a given quantization step size and vice versa. The most attactive features of proposed distortion-rate estimation are its accuracy and low computational complexity enough to be applied to the practical video coding. In addition, the proposed rate control first determined a quantization parameter per frame by following procedure: distortion-rate estimation, target bit allocation, distortion constraint and VBV(Video Buffer Verification) constraint. And then this quantization parameter is applied to the encoding so that improved and consisten picture quality can be obtained. Furthermore the proposed rate control method can solve the error propagation problem caused by scene change or anchor picture degradation by using the B-picture skipping and the guarantee of the minimum bit allocation for the anchor picture. Experimental results, comparing the proposed forward rate control method with TM5 method, show that the proposed method makes more improed and consistent picture quality than TM5.

• Journal of Broadcast Engineering
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• v.3 no.1
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• pp.69-84
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• 1998

In digital broadcasting, services such as digital satellite TV, cable TV and digital terrestrial TV, several video programs are compressed by MPEG-2, and then simultaneously transmitted over a conventional CBR (Constant Bit Rate) broadcasting channel. In this paper, we propose a joint quality control scheme to be able to accurately control the relative picture quality among the video programs, which is achieved by simdt;,nL'Ously controlling the video encoders to generate the VBR (Variable Bit Rate) compressed video streams. Our quality control scheme can prevent the video buffer overflow and underflow by total target bit allocation process, and also exactly control the relative picture quality in terms of PSNR (Peak Signal to Noise Ratio) between some programs requiring higher picture quality and others by rate-distortion modification. Furthermore we present a rate-distortion estimation method for MPEG-2 video, which is base of our joint quality control, and verify its performance by experiments. The most attractive features of this estimation method are as follows: 1) computational complexity is low because main operation for the estimation is to calculate the histogram of OCT coefficients into quantizer; 2) estimation results are very accurate enough to be applied to the practical MPEG-2 video coding applications. Simulation results show that the proposed joint quality control scheme accurately controls the relative picture quality among the video progran1s transmitted over a single channel as well as provides more consistent and higher picture quality than independent coding scheme that encodes each program independently.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.1024-1026
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• 2013

DVC (Distributed Video Coding) techniques provides a basic theory for the implementation of low-power video encoder. Conventional methods decide the parity bit request at decoder side. These are effective in controlling the bit-rate, but, are not able to control the visual quality. Thus, this paper presents an effective method of estimating visual quality improved by correcting the virtual channel noise for the reconstructed frame. Through several experiments, it is shown that the proposed method are able to estimate effectively the decoded visual quality.