• Title/Summary/Keyword: 비트율 제어

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Adaptive Basic Unit Level Rate Control for H.264 (적응적 베이직 유닛 레벨 H.264 비트율 제어)

  • Park, Sang-Hyun
    • 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.

Wireless Measurement based TFRC for QoS Provisioning over IEEE 802.11 (IEEE 802.11에서 멀티미디어 QoS 보장을 위한 무선 측정 기반 TFRC 기법)

  • Pyun Jae young
    • 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.

A Feedback Buffer Control Algorithm for H.264 Video Coding (H.264 동영상 부호기를 위한 Feedback 버퍼 제어 방식)

  • Son Nam Rye;Lee Guee Sang
    • 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.

An R-lambda Model based Rate Control Scheme to Support Parallel GOP Coding for Real-Time HEVC Software Encoders (HEVC 실시간 소프트웨어 인코더를 위한 GOP 병렬 부호화를 지원하는 R-lambda 모델 기반의 율 제어 방법)

  • Kim, Dae Eun;Chang, Yongjun;Kim, Munchurl;Lim, Woong;Kim, Huiyong;Seok, Jinwuk
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • 2016.11a
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    • pp.107-109
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    • 2016
  • 본 논문에서는 4K UHD 입력 영상을 실시간으로 부호화하기 위해 적용되는 GOP 단위 또는 IDR 주기 단위의 병렬 부호화 구조를 지원하도록 R-${\lambda}$ 모델 기반의 율 제어 방법을 개선하는 비트 분배(bit allocation) 방법을 제안한다. GOP 단위 또는 IDR 주기 단위의 병렬 부호화기 내에서 율 제어기를 작동시키는 경우, 계층적 B 구조에서 같은 계층에 있는 프레임 간에는 상호간에 얼마만큼의 비트를 소모 하였는지에 대한 정보를 공유 할 수 없기 때문에 기존의 비트 분배 방식으로는 비트 예산(bit budget) 관리가 불가능하다. 이를 해결하기 위해 본 논문에서는, 기존의 R-${\lambda}$ 모델 기반 율 제어 방법을 개선하여 부호화 순서에 의한 시간 순서 방향의 비트 예산 갱신 기반 비트 분배하던 방식으로부터, GOP 마다 비트를 할당한 후 계층적 B 구조에서의 계층이 깊어지는 방향으로 비트 예산을 갱신하여 비트를 분배하는 방식으로 율 배분 방식을 개선하였다. 실험 결과를 통해 R-${\lambda}$ 모델 기반 율 제어의 기존 비트 분배 방식보다 제안 방법에 의한 목표 비트 율 달성 오차가 감소함을 확인하였다.

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H.264/AVC Rate Control for Scene Change with Complexity of Sequence (영상의 복잡도를 이용한 장면 전환 추정과 H.264/AVC 비트율 제어)

  • Kim, Jong-Gu;Suh, Jae-Won
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • 2009.11a
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    • pp.299-302
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    • 2009
  • 본 논문에서는 프레임 안에서의 인접픽셀간의 복잡도를 이용하여 할당비트 조절과 장면 전환을 추정하는 H.264/AVC 비트율 제어 기법을 제안한다. Quadratic 율-왜곡 모델은 프레임 할당 비트와 선형 모델을 통해 예측된 MAD정보를 필요로 한다. 이때 장면전환과 같은 급격한 화질 변화는 예측된 MAD정보만으로는 적합한 양자화파라미터를 결정하지 못하고 이후 비트율 제어를 어렵게 한다. 제안하는 방법은 프레임 안에서 인접픽셀간의 차분 값들의 절대 합을 구하여 이전프레임과 현제프레임의 비로 나타낸 후 이 값의 일정 범위를 벗어나면 장면전환이 이루어진 것으로 간주하여 이에 알맞은 양자화 파라미터 결정기법을 적용하도록 하였다.

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A bit-rate control of MPEG-2 video coding using quantization ratio coefficient and the mean MQUANT (양자화 비례 계수와 평균 MQUANT를 이용한 MPEG-2 비디오 부호화 비트율 제어)

  • 이근영;임용순;김주도;한승욱
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.23 no.8
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    • pp.2025-2031
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    • 1998
  • In moving picture coding standard MPEG2, a bit rate control system plays a key role for the compressing ratio and picture quality. We proposed a bit rate control scheme which assigns more bits to I, P frames and uses the average MQUANT of previous mackoblocks. The proposed scheme showed about 0.9dB improvement of image quality when compared to bit rate control method of MPEG2 Test-Model5.

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Joint Rate Control Scheme for Terrestrial Stereoscopic 3DTV Broadcast (스테레오스코픽 3차원 지상파 방송을 위한 합동 비트율 제어 연구)

  • Chang, Yongjun;Kim, Munchurl
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • 2010.11a
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    • pp.14-17
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    • 2010
  • Following the proliferation of three-dimensional video contents and displays, many terrestrial broadcasting companies prepare for starting stereoscopic 3DTV service. In terrestrial stereoscopic broadcast, it is a difficult task to code and transmit two video sequences while sustaining as high quality as 2DTV broadcast attains due to the limited bandwidth defined by the existing digital TV standards such as ATSC. Thus, a terrestrial 3DTV broadcasting system with heterogeneous video coding systems is considered for terrestrial 3DTV broadcast where the left image and right images are based on MPEG-2 and H.264/AVC, respectively, in order to achieve both high quality broadcasting service and compatibility for the existing 2DTV viewers. Without significant change in the current terrestrial broadcasting systems, we propose a joint rate control scheme for stereoscopic 3DTV service. The proposed joint rate control scheme applies to the MPEG-2 encoder a quadratic rate-quantization model which is adopted in the H.264/AVC. Then the controller is designed for the sum of two bit streams to meet the bandwidth requirement of broadcasting standards while the sum of image distortions is minimized by adjusting quantization parameter computed from the proposed optimization scheme. Besides, we also consider a condition on quality difference between the left and right images in the optimization. Experimental results demonstrate that the proposed bit rate control scheme outperforms the rate control method where each video coding standard uses its own bit rate control algorithm in terms of minimizing the mean image distortion as well as the mean value and the variation of absolute image quality differences.

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Bit-Rate Control Using Histogram Based Rate-Distortion Characteristics (히스토그램 기반의 비트율-왜곡 특성을 이용한 비트율 제어)

  • 홍성훈;유상조;박수열;김성대
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.24 no.9B
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    • pp.1742-1754
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    • 1999
  • In this paper, we propose a rate control scheme, using histogram based rate-distortion (R-D) estimation, which produces a consistent picture quality between consecutive frames. The histogram based R-D estimation used in our rate control scheme offers a closed-form mathematical model that enable us to predict the bits and the distortion generated from an encoded frame at a given quantization parameter (QP) and vice versa. The most attractive feature of the R-D estimation is low complexity of computing the R-D data because its major operation is just to obtain a histogram or weighted histogram of DCT coefficients from an input picture. Furthermore, it is accurate enough to be applied to the practical video coding. Therefore, the proposed rate control scheme using this R-D estimation model is appropriate for the applications requiring low delay and low complexity, and controls the output bit-rate ad quality accurately. Our rate control scheme ensures that the video buffer do not underflow and overflow by satisfying the buffer constraint and, additionally, prevents quality difference between consecutive frames from exceeding certain level by adopting the distortion constraint. In addition, a consistent considering the maximum tolerance BER of the voice service. Also in Rician fading channel of K=6 and K=10, considering CLP=$10^{-3}$ as a criterion, it is observed that the performance improment of about 3.5 dB and 1.5 dB is obtained, respectively, in terms of $E_b$/$N_o$ by employing the concatenated FEC code with pilot symbols.

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Improving Video Quality with Bitrate Control and Visual Recognition in H.264/AVC (H.264/AVC에서 비트율 제어와 시각 인지도를 고려한 영상화질 개선 기법)

  • Ahn, Soomin;Kim, Kangseok;Kim, Jai-Hoon
    • 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.