• Title/Summary/Keyword: Distortion Estimation

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Efficient Rolling Shutter Distortion Removal using Hierarchical Block-based Motion Estimation

  • Lee, Donggeun;Choi, Kang-Sun
    • IEIE Transactions on Smart Processing and Computing
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    • v.3 no.4
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    • pp.205-211
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    • 2014
  • This paper reports an efficient algorithm for accurate rolling shutter distortion removal. A hierarchical global motion estimation approach for a group of blocks reduces the level of computation by three orders of magnitude. In addition, the motion of each scanline is determined accurately by averaging two candidates obtained through cubic spline interpolation. The experimental results show that the proposed method produces accurate motion information with significant computation reduction and corrects the rolling shutter distortion effectively.

Frame-Adaptive Distortion Estimation for Motion Compensated Interpolated Frame (움직임 보상 보간 프레임에 대한 프레임 적응적 왜곡 예측 기법)

  • Kim, Jin-Soo
    • The Journal of the Korea Contents Association
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    • v.12 no.3
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    • pp.1-8
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    • 2012
  • Video FRUC (Frame Rate Up Conversion) has been a technique of great interest due to its diversified applications in consumer electronics. Most advanced FRUC algorithms adopt a motion interpolation technique to determine the motion vector field of interpolated frames. But, in some applications, it is necessary to evaluate how well the MCI (Motion Compensated Interpolation) frame is reconstructed. For this aim, this paper proposes a distortion estimation for motion compensated interpolation frame using frame-adaptive distortion estimation. The proposed method is applied for the symmetric motion estimation and compensated scheme and then analyzed by three different approaches, that is, forward estimation, backward estimation and adaptive bi-directional estimation schemes. Through computer simulations, it is shown that the proposed bi-directional estimation method outperforms others and can be effectively applied for FRUC.

Correction of Signboard Distortion by Vertical Stroke Estimation

  • Lim, Jun Sik;Na, In Seop;Kim, Soo Hyung
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.7 no.9
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    • pp.2312-2325
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    • 2013
  • In this paper, we propose a preprocessing method that it is to correct the distortion of text area in Korean signboard images as a preprocessing step to improve character recognition. Distorted perspective in recognizing of Korean signboard text may cause of the low recognition rate. The proposed method consists of four main steps and eight sub-steps: main step consists of potential vertical components detection, vertical components detection, text-boundary estimation and distortion correction. First, potential vertical line components detection consists of four steps, including edge detection for each connected component, pixel distance normalization in the edge, dominant-point detection in the edge and removal of horizontal components. Second, vertical line components detection is composed of removal of diagonal components and extraction of vertical line components. Third, the outline estimation step is composed of the left and right boundary line detection. Finally, distortion of the text image is corrected by bilinear transformation based on the estimated outline. We compared the changes in recognition rates of OCR before and after applying the proposed algorithm. The recognition rate of the distortion corrected signboard images is 29.63% and 21.9% higher at the character and the text unit than those of the original images.

Simplified Approach for Distortion Estimation in H.264 (H.264에서 간소화된 기법에 의한 왜곡치 예측)

  • Park, Ki-Hong;Kim, Yoon-Ho
    • Journal of Advanced Navigation Technology
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    • v.14 no.3
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    • pp.446-451
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    • 2010
  • This paper addressed an another scheme of distortion estimation method based on simplified inverse quantization in H.264/AVC. The distortion is calculated by the difference of coefficient between quantized transform coefficients and that of inverse. In general, these process included such transforms as discrete cosine transform(DCT), quantization, inverse quantization(IQ), and Inverse DCT(IDCT). In proposed approach, IQ as well as IDCT process are skipped because of replacing a couple of approximated formulas. Some simulation have been conducted and it showed that the PSNR was almost the same, and reduced the rate-distortion optimization(RDO) mode decision time of 8~15% in comparison with conventional method.

An Adaptive Control for the Propagation Errors Incurred by DCT Coefficient-Dropping Transcoder

  • Kim, Jin-Soo;Kim, Jae-Gon;Seo, Kwang-Deok;Yun, Mong-Han
    • ETRI Journal
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    • v.29 no.5
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    • pp.559-568
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    • 2007
  • This paper presents a new distortion control scheme with a simple estimation model for the propagation errors incurred by dropping some parts of the bitstream in a frame dropping-coefficient dropping (FD-CD) transcoder. The primary goal of this paper is to facilitate bit-rate conversions and rate-distortion controls in the compressed domain without introducing a full decoding and reencoding system in the pixel domain. First, the error propagation behavior over several frame sequences due to coefficient dropping is investigated on the basis of statistical and empirical properties. Then, such properties are used to develop a simple estimation model for the CD distortion accounting for the characteristics of the underlying coded-frame. Finally, the proposed estimation model allows us to determine the amount of coefficient dropping and to effectively allocate rate-distortions into coded-frames. Experimental results show that the proposed estimation model accurately describes the characteristics of propagation errors adaptively in the compressed domain and can be easily applied to distortion control over different kinds of video sequences.

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A Rate-Distortion Estimation Method for Fast Mode Decision in H.264 (H.264에서 고속의 모드 결정을 위한 율-왜곡 예측 방식)

  • Moon, Jeong-Mee;Kim, Jae-Ho
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.1C
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    • pp.34-44
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    • 2008
  • In this paper, a new rate-distortion estimation method is proposed for fast rate-distortion optimized(RDO) mode decision in H.264 encoder. A bit-rate and distortion should be calculated by encoding and reconstruction of each macroblock mode in order to select the optimal RDO mode. To reduce the computations for getting them, a bit-rate and distortion is efficiently estimated in DCT domain. Simulation results show that the proposed method achieves computational saving about 81% of RDO mode decision and saves about 26% of total encoding time without noticeable degradation in coding performance.

Improved Rate-Distortion Estimation for Mode Decision in H.264/AVC (H.264/AVC에서 모드 결정을 위한 개선된 율-왜곡 예측)

  • Park, Ki-Hong;Kim, Yoon-Ho
    • Journal of Advanced Navigation Technology
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    • v.14 no.1
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    • pp.102-107
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    • 2010
  • This paper presented a rate-distortion estimation method for effective mode decision in H.264/AVC. In this approach, in order to decide a mode, laplacian distribution modeling of DCT coefficients is utilized, which do not need to such process as quantization, entropy coding. From the simulation results, proposed a method showed that rate-distortion between proposed scheme and practical value was almost the same and performed 0.02dB of PSNR gain.

Automatic Estimation of Spatially Varying Focal Length for Correcting Distortion in Fisheye Lens Images

  • Kim, Hyungtae;Kim, Daehee;Paik, Joonki
    • IEIE Transactions on Smart Processing and Computing
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    • v.2 no.6
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    • pp.339-344
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    • 2013
  • This paper presents an automatic focal length estimation method to correct the fisheye lens distortion in a spatially adaptive manner. The proposed method estimates the focal length of the fisheye lens by generating two reference focal lengths. The distorted fisheye lens image is finally corrected using the orthographic projection model. The experimental results showed that the proposed focal length estimation method is more accurate than existing methods in terms of the loss rate.

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Position Estimation Using Magnetic Field Map (자기장 지도를 이용한 위치 추정)

  • Kim, Han-Sol;Moon, Woo-Sung;Seo, Woo-Jin;Baek, Kwang-Ryul
    • Journal of Institute of Control, Robotics and Systems
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    • v.19 no.4
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    • pp.290-298
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    • 2013
  • Geomagnetic is refracted by building's wall and pillar. Therefore refracted geomagnetic is able to be used as feature point. In a specific space, a mobile device that is equipped with magnetic sensor array measures 3-axis magnetic field for each point. Magnetic field map is acquired by collecting the every sample point in the magnetic field. The measured magnetic field must be calibrated, because each magnetic sensor has a distortion. For this reason, sensor distortion model and sensor calibration method are proposed in this paper. Magnetic field that is measured by mobile device matches magnetic field map. Result of the matching is used for position estimation. This paper implements hardware system for position estimation method using magnetic field map.

A Distortion Estimation Method Using Integer Operations in H.264/AVC Encoder (H.264/AVC 부호화기에서 정수 연산을 사용한 왜곡치 예측 방식)

  • Moon, Jeong-Mee;Kim, Jae-Ho
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.1C
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    • pp.63-71
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    • 2009
  • In this paper, a new low-complexity distortion estimation method for H.264 rate-distortion optimized mode decision is proposed. The coding processes, such as DCT, quantization, inverse quantization, inverse DCT, and reconstruction are needed to compute the distortion in an H.264 encoder. To reduce these processes, we estimate distortion using integer operations with coefficients obtained in the quantization process. Inverse quantization, inverse DCT, and reconstruction processes are not needed by the proposed method. For quantization parameters 24 to 36, experimental results show that the time saving of rate-distortion optimized mode decision is on average 29 % and as high as 42 % with negligible degradation in coding performance.