• Proceedings of the IEEK Conference
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• 2003.07e
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• pp.2064-2067
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• 2003

본 논문에서는 비트율 제어 (rate-control)와 혼잡 제어(congestion-control) 사이의 관계를 고려하여 비디오데이터의 전송량 변화에 따른 화질 증감의 관계를 조사하고, 전송 대역폭의 변화에 대한 화질 열화를 최소화하기 위한 비디오 데이터 전송량의 변화 조건을 제안하고자 한다. 비디오 데이터를 전송하는 경우에 혼잡 제어는 현 채널 상에서 가용 전송 대역폭(Available Transmission Bandwidth)을 예측하고, 비트율 제어는 예측한 전송 대역폭을 비디오 부호화기의 전송 비트율에 적응시킨다. AIMD 기반의 혼잡 제어 기법은 비디오 데이터의 목표 비트율 (target bit rate)을 변화시키게 되고 이러한 결과는 비디오 화질의 잦은 변동으로 인해 나쁜 영향을 준다. 이러한 문제를 해결하기 위해 QP, SNR, 비트량 사이의 관계를 이용한 적응적인 메커니즘을 제안하고자 한다

• Proceedings of the Korea Information Processing Society Conference
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• 2014.11a
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• pp.971-974
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• 2014

H.264/AVC 영상 부호화기의 비트율(Bitrate) 제어에 사람의 눈에 잘 인식되는 부분의 화질을 향상하고 인식률이 낮은 부분의 화질을 낮추어 상대적으로 향상된 화질을 얻기 위한 방법을 연구하였다. 먼저 H.264/AVC 영상 부호화기에서, 장면 변화로 인한 참조 프레임의 비트 낭비를 막기 위해 GOP(Group of Pictures) 단위로 장면 변화를 검출한 후, 검출된 장면 변화에 대해 GOP를 적용 시킨다. 해당 GOP 내에서 시각 인지도에 기초하여 물체의 움직임으로 인한 인식률이 높은 부분을 검출하고, 인식률이 높은 부분에 대해 QP(Quantization Parameter)의 재분배로 비트율을 높임으로써 화질을 향상시키고, 인식률이 낮은 부분에 대해서는 비트율을 적게 분배한다. 그 결과 한정된 대역폭을 갖는 전송 환경에서 영상을 향상된 화질로 이용할 수 있는 방법을 제안한다.

• Journal of Broadcast Engineering
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• v.10 no.4 s.29
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• pp.488-504
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• 2005

In this paper, we propose a new bitrate control scheme to improve the quality of image encoded by SVC and to resolve the problems of conventional scheme. In JSVM2.0, bitrate of a frame is controlled by an initial quantization parameter and scaling factor that it hasdifferent value according to frame. Itis difficult to get the best of video quality at arbitrary bitrate because the conventional scheme has two defects. One is that we have to know proper initial QP's fur all sequences. Another is that QP's control skill for macroblocks is very inefficient. In this paper, we propose an efficient bit allocation algorithm to reduce the effect of the initial QP and to increase the efficiency of bit allocation by using proper QP's for macroblocks. In simulation results, it can be seen that using the proposed scheme enables the SVC encoder to control the bitrate by the macroblock unit and outperforms the conventional schemes in the respect of rate-distortion.

• Journal of Korea Multimedia Society
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• v.9 no.7
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• pp.818-826
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• 2006

In this paper, we investigate the relationship of bitrate and quantization parameter needed for the trans-coding method that makes the H.264 bitstream of a particular bitrate to the other titrate. Also we propose the new method in order to transcode the titrate between H.264 video coded bitstreams. The proposed transcoding method updates the model parameters from previous picture or slice by using the approximated relationship of bitrate and quantization step-size and finds the target quantization step-size, and then generates the target titrate by simple coding processing just after requantization. Therefore, the proposed method does not need the complex bitrate control and converts to the target titrate by simple implementation. From simulation, we can see that the proposed method transcodes exactly to an assigned target bitrate for the four test sequences with different their characteristics.

• Journal of the Institute of Convergence Signal Processing
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• v.6 no.4
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• pp.176-181
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• 2005

This paper presents an equal bit rate control algorithm utilizing the statistical change between the previous frame and the current frame. The previous studies on the model-based rate control have focused on the models of bit rate and distortion in types of coders, in terms of the quantization parameter. The proposed algorithm improves the typical model-based rate control by updating a model parameter instead of modeling a better model of the rate and distortion. The proposed algorithm updates this model parameter by recognizing the change in statistics between the previous frame and the current frame. We implement the proposed algorithm in MPEG-4 coders and verify its performance while comparing it to the TMN8's approach (up to 0.6dB of improvement).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.2
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• pp.355-361
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• 2009

This paper proposes a new basic unit level rate control algorithm which generates the output bits corresponding to the target bits. The H.264 standard uses various coding modes and optimization methods to improve the compression performance, which makes it difficult to control the generated traffic accurately. In the proposed scheme, the allocated bits to a frame are distributed to all basic units properly to encode each basic unit according to the bit budget. After encoding the frame, the encoding parameters are adjusted according to the difference between the target and the resulting values. It is shown by experimental results that the new algorithm can generate output bit rates accurately corresponding to the target bit rates with the PSNR performance better than that of the existing rate control algorithm.

• Journal of Korea Multimedia Society
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• v.11 no.5
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• pp.579-587
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• 2008

Typically, the file sizes of JPEG compressed images with various complexity differ from images regardless of same image size. So, it is not easy to estimate the remaining image counts that should be stored in the limited storage equipped with the digital camera. To solve the problem, the bit rate control employs the modification of quantization table. The previous work assumed that there is linear relation between image activity and modification factor of quantization table, but in this paper, more accurate functional relations based on statistics are employed to improve the bit rate control accuracy. Computer simulations reveals that the standard deviation of the bit rate error of the proposed scheme is 50% less than that of the conventional method.

• The Journal of the Acoustical Society of Korea
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• v.21 no.3
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• pp.315-322
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• 2002

In this paper, a new temporal decomposition method is proposed. which takes into consideration not only spectral distortion but also bit rates. The interpolation functions, which are one of necessary parameters for temporal decomposition, are obtained from the training speech corpus. Since the interval between the two targets uniquely defines the interpolation function, the interpolation can be represented without additional information. The locations of the targets are determined by minimizing the bit rates while the maximum spectral distortion maintains below a given threshold. The proposed method has been applied to compressing the LSP coefficients which are widely used as a spectral parameter. The results of the simulation show that an average spectral distortion of about 1.4 dB can be achieved at an average bit rate of about 8 bits/Frame.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.4B
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• pp.202-209
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• 2005

In this paper, a dynamic TCP-friendly rate control (TFRC) is proposed to adjust the coding rates according to the channel characteristics of the wireless-to-wired network consisting of wireless first-hop channel. To avoid the throughput degradation of multimedia flows traveling through wireless lint the proposed rate control system employs a new wireless loss differentiation algorithm (LDA) using packet loss statistics. This method can produce the TCP-friendly rates while sharing the backbone bandwidth with TCP flows over the wireless-to-wired network. Experimental results show that the proposed rate control system can eliminate the effect of wireless losses in flow control of TFRC and substantially reduce the abrupt quality degradation of the video streaming caused by the unreliable wireless link status.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06e
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• pp.215-218
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• 1998

본 논문에서는 가변블록에 대해 DCT와 VQ를 적용함으로써 복원시 영상의 품질을 원하는 수준으로 유지하면서 비트율을 감소시키는 방법을 제안한다. 각 블록에 대해 임계값에 따라 블록의 크기를 세분화 시켜 하위 블록에 대해 DCT와 VQ를 적용한다. 임계값 결정 방법은 원 화소의 최대군과 최소군의 편차를 이용하였다. 제안된 방법은 화소의 변화가 급격한 영상에서는 비트율이 0.34~0.47bpp가 감소하였고, 화소의 변화가 적은 영상에서는 0.74~0.79bpp정도 개선할 수 있다.