• Title, Summary, Keyword: Initial QP

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Adaptive Initial QP Determination Algorithm for Low Bit Rate Video Coding (저전송률 비디오 압축에서 적응적 초기 QP 결정 알고리즘)

  • Park, Sang-Hyun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.14 no.9
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    • pp.1957-1964
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    • 2010
  • In Video coding, the first frame is encoded in intra mode which generates a larger number of bits. In addition, the first frame is used for the inter mode encoding of the following frames. Thus the intial QP for the first frame of GOP affects the first frame as well as the following frames. Traditionally, the initial QP of a GOP is determined by the initial QP of the previous GOP and the average QP of the inter mode frames. In case of JM, the initial QP of a GOP is adjusted as the initial QP being less than the average QP of inter mode frames by two. However, this method is not suitable for the low bit rate video coding. In this paper, the linear relationship between the optimal QP and the ratio of the PSNR of the first frame and the average PSNR of the inter mode frames is first investigated and the linear model is proposed based on the results of the investigation. The proposed model calculate the optimal initial QP using the encoding results of the previous GOP. It is shown by experimental results that the new algorithm can predict the optimal initial QP more accurately and generate the PSNR performance better than that of the existing JM algorithm.

Initial QP Determination Algorithm using Bit Rate Model (비트율 모델을 이용한 초기 QP 결정 알고리즘)

  • Park, Sang-Hyun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.16 no.9
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    • pp.1947-1954
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    • 2012
  • The first frame is encoded in intra mode which generates a larger number of bits. In addition, the first frame is used for the inter mode encoding of the following frames. Thus the initial QP for the first frame affects the first frame as well as the following frames. Traditionally, the initial QP is determined among four constant values only depending on the bpp. In the case of low bit rate video coding, the initial QP value is fixed to 40 regardless of the output bandwidth. Although this initialization scheme is simple, yet it is not accurate enough. An accurate initial QP prediction scheme should not only depends on bpp but also on the complexity of the video sequence and the output bandwidth. In the proposed scheme, we determine the initial QP according to the ratio of the first frame to the total bits allocated to a GOP. To estimate the QP of the allocated bits, Rate-QP model is used. It is shown by experimental results that the new algorithm can predict the optimal initial QP more accurately and generate the PSNR performance better than that of the existing JVT algorithm.

Optimal QP Determination Method for Adaptive Intra Frame Encoding (적응적 인트라 프레임 압축을 위한 최적 QP 결정 방법)

  • Park, Sang-Hyun
    • The Journal of the Korea institute of electronic communication sciences
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    • v.10 no.9
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    • pp.1009-1018
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    • 2015
  • In video coding, the first frame of a GOP is encoded in intra mode which generates a larger number of bits. In addition, the first frame is used for the inter mode encoding of the following frames. Thus the intial QP for the first frame encoding affects the first frame as well as the following frames. To determine the initial QP that maximizes the PSNR of a GOP, several algorithms which uses the ratio of the PSNR of the I frame and the PSNR of P frames of a GOP have been proposed. In this paper, we propose a new traffic model that can be used to determine the optimal initial QP simply and exactly in algorithms that use the PSNR ratio. We first analyze the characteristics of the PSNR ratio of I and P frames and the PSNR of a GOP, and then propose a new traffic model which can represent the characteristics and determine the optimal intial QP. It is shown by experimental results that the initial QP determination method with the proposed model can predict an optimal initial QP whose difference from the optimal value is less than 2. The proposed scheme can also generate the PSNR performance better than that of the existing JVT algorithm.

Initial QP Modeling for GOP Layer Rate Control (GOP 레이어 비트율 제어를 위한 초기 QP 모델링)

  • Park, Sang-Hyun
    • The Journal of the Korea institute of electronic communication sciences
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    • v.7 no.6
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    • pp.1377-1383
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    • 2012
  • The first frame of a GOP is encoded in intra mode which generates a larger number of bits. In addition, the first frame is used for the inter mode encoding of the following frames. Thus the intial QP for the first frame affects the first frame as well as the following frames. Traditionally, the initial QP is determined among four constant values only depending on the bpp. Although this initialization scheme is simple, yet it is not accurate enough. An accurate intial QP prediction scheme should not only depends on bpp but also on the complexity of the video sequence and the output bandwidth. In this paper, we propose a traffic model for finding the optimal initial QP which maximizes the PSNR of the GOP. We also propose a method to find model parameters for real-time video encoding. It is shown by experimental results that the proposed traffic model captures initial QP characteristics effectively and the proposed method for model parameters accurately estimates the real values.

PSNR-based Initial QP Determination for Low Bit Rate Video Coding

  • Park, Sang-Hyun
    • Journal of information and communication convergence engineering
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    • v.10 no.3
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    • pp.315-320
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    • 2012
  • In H.264/AVC, the first frame of a group of pictures (GOP) is encoded in intra mode which generates a large number of bits. The number of bits for the I-frame affects the qualities of the following frames of a GOP since they are encoded using the bits remaining among the bits allocated to the GOP. In addition, the first frame is used for the inter mode encoding of the following frames. Thus, the initial quantization parameter (QP) affects the following frames as well as the first frame. In this paper, an adaptive peak signal to noise ratio (PSNR)-based initial QP determination algorithm is presented. In the proposed algorithm, a novel linear model is established based on the observation of the relation between the initial QPs and PSNRs of frames. Using the linear model and PSNR results of the encoded GOPs, the proposed algorithm accurately estimates the optimal initial QP which maximizes the PSNR of the current GOP. It is shown by experimental results that the proposed algorithm predicts the optimal initial QP accurately and thus achieves better PSNR performance than that of the existing algorithm.

Initial QP Determination Algorithm for Low Bit Rate Video Coding (저전송률 비디오 압축에서 초기 QP 결정 알고리즘)

  • Park, Sang-Hyun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.13 no.10
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    • pp.2071-2078
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    • 2009
  • The first frame is encoded in intra mode which generates a larger number of bits. In addition, the first frame is used for the inter mode encoding of the following frames. Thus the intial QP (Quantization Parameter) for the first frame affects the first frame as well as the following frames. Traditionally, the initial QP is determined among four constant values only depending on the bpp. In the case of low bit rate video coding, the initial QP value is fixed to 35 regardless of the output bandwidth. Although this initialization scheme is simple, yet it is not accurate enough. An accurate intial QP prediction scheme should not only depends on bpp but also on the complexity of the video sequence and the output bandwidth. In the proposed scheme, we use a linear model because there is a linear inverse proportional relationship between the output bandwidth and the optimal intial QP. Model parameters of the model are determined depending on the spatial complexity of the first frame. It is shown by experimental results that the new algorithm can predict the optimal initial QP more accurately and generate the PSNR performance better than that of the existing JM algorithm.

The First Quantization Parameter Decision Algorithm for the H.264/AVC Encoder (H.264/AVC를 위한 초기 Quantization Parameter 결정 알고리즘)

  • Kwon, Soon-Young;Lee, Sang-Heon;Lee, Dong-Ha
    • Journal of KIISE:Information Networking
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    • v.35 no.3
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    • pp.235-242
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    • 2008
  • To improve video quality and coding efficiency, H.264/AVC adopted an adaptive rate control. But this method has a problem as it cannot predict an accurate quantization parameter(QP) for the first frame. The first QP is decided among four constant values by using encoder input parameters. It does not consider encoding bits, results in significant fluctuation of the image quality and decreases the average quality of the whole coded sequence. In this paper, we propose a new algorithm for the first frame QP decision in the H.264/AVC encoder. The QP is decided by the existing algorithm and the first frame is encoded. According to the encoded bits, the new initial QP is decided. We can predict optimal value because there is a linear relationship between encoded bits and the new initial QP. Next, we re-encode the first frame using the new initial QP. Experimental results show that the proposed algorithm not only achieves better quality than the state of the art algorithm, but also adopts a rate control forthe sequence that was impossible with the existing algorithm. By reducing fluctuation, subjective quality also improved.

R-Q Modeling for H.264/AVC Rate Control (H.264/AVC 비트율 제어를 위한 R-Q 모델링)

  • Park, Sang-Hyun
    • The Journal of the Korea institute of electronic communication sciences
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    • v.8 no.9
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    • pp.1325-1332
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    • 2013
  • The first frame of a GOP, an I frame, is encoded in intra mode which generates a larger number of bits. In addition, the I frame is used for the inter mode encoding of the following frames. Thus the intial QP for the I frame affects the first frame as well as the following frames. In our previous work, we analyzed the number of bits for an I frame and showed that the ratio of the number of bits which maximizes the PSNR of a GOP maintains similar value regardless of GOP's. In this paper, we propose a R-Q model which can be used for the calculation of the initial QP given the amount of bits for an I frame. The proposed model is simple and adaptively modifies model parameters, so it can be applicable to the real-time application. It is shown by experimental results that the proposed model captures initial QP characteristics effectively and the proposed method for model parameters accurately estimates the real values.

Efficient Bitrate Control Scheme for Scalable Video Codec (Scalable Video Codec을 위한 효율적인 비트율 제어기법)

  • Park Nae-Ri;Jeon Dong-San;Kim Jae-Gon;Han Jong-Ki
    • Journal of Broadcast Engineering
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    • v.10 no.4
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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.

Characteristics of the E- and F-region field-aligned irregularities in middle latitudes: Initial results obtained from the Daejeon 40.8 MHz VHF radar in South Korea

  • Kwak, Young-Sil;Yang, Tae-Yong;Kil, Hoysub;Phanikumar, Devulapalli Venkata;Heo, Bok-Haeng;Lee, Jae-Jin;Hwang, Junga;Choi, Seong-Hwan;Park, Young-Deuk;Choi, Ho-Seong
    • Journal of Astronomy and Space Sciences
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    • v.31 no.1
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    • pp.15-23
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    • 2014
  • We present preliminary observations of the field-aligned-irregularities (FAIs) in the E and F regions during the solar minimum (2009 - 2010) using the 40.8 MHz coherent backscatter radar at Daejeon ($36.18^{\circ}N$, $127.14^{\circ}E$, $26.7^{\circ}N$ dip latitude) in South Korea. The radar, which consists of 24 Yagi antennas, observes the FAIs using a single beam with a peak power of 24 kW. The radar has been continuously operated since December 2009. Depending on the manner of occurrence of the backscatter echoes, the E-region echoes are largely divided into two types: quasi-periodic (QP) and continuous echoes. Our observations show that the QP echoes occur frequently above an altitude of 105 km in the post-sunset period and continuous echoes occur preferentially around an altitude of 105 km in the post-sunrise period. QP echoes appear as striated discrete echoes for a period of about 10 - 20 min. The QP-type echoes occur more frequently than the continuous-type echoes do and the echo intensity of the QP type is stronger than that of the continuous type. In the F region, the FAIs occur at night at an altitude interval of 250 - 450 km. As time proceeds, the occurrence height of the FAIs gradually increases until early in the morning and then decreases. The duration of the F-region FAIs is typically a few hours at night, although, in rare cases, FAIs persist throughout the night or appear even after sunrise. We discuss the similarities and differences of the FAIs observed by the Daejeon radar in comparison with other radar observations.