Yannan Wu

The Hong Kong University of Science and Technology, Chiu-lung, Kowloon City, Hong Kong

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Publications (9)0 Total impact

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    ABSTRACT: In advance of the imaging capturing technology, large amount of similar images are created. Instead of compressing each similar image individually, removing the inter-image redundancy would reduce the storage and transmission time. However, only a few set redundancy methods are proposed to deal with the problem. In this paper, a new method was derived from a theoretical model by extracting the low frequency in an image set. For the similar images, the values of their low frequency components are very close to that of their neighboring pixel in the spatial domain. In our model, a low frequency template is created and used as a prediction for each image to compute its residue. This model proves the reduction in the entropy and hence the bit rates. Experiments were conducted and proved there were up to 30% gains over the existing methods.
    Proceedings of the 2011 IEEE International Conference on Multimedia and Expo, ICME 2011, 11-15 July, 2011, Barcelona, Catalonia, Spain; 01/2011
  • Chi-Ho Yeung · O. C. Au · Shing-Fat Tu · Yannan Wu · Enming Luo ·
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    ABSTRACT: Most researches on oriental calligraphies simulation are based on the texture rendering methods with input from pointing devices. However, the traditional way is by using the hairy brush which is not employed in these applications. In this paper, we proposed a novel multimedia human computer interface that allows users which including artists to use the physical hairy brushes to write without training, so as to provide the same user experience. A virtual paper is projected on the transparent screen, the interface for using the hairy brush. An infra-red camera is used in capturing the image as the system input. A software framework was proposed to compute the contact region and the ink absorption between the ink-brush and the virtual paper. This information is highly useful in further rendering the texture of the brushstrokes and the ink spreading on the paper.
  • Enming Luo · Oscar C.L. Au · Liwei Guo · Yannan Wu · Shing Fat Tu ·
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    ABSTRACT: Recently, many schemes that embed the denoising process into the video encoding have been proposed. They are mainly implemented into the single-layer encoder, like the H.264 reference encoder joint model (JM). In this paper, we propose to embed the denoising process into the multi-layer spatial SVC encoder. Since either for the base layer or the enhancement layer our proposed filter could achieve linear minimum mean square error (LMMSE) and meanwhile the additional inter-layer prediction tools could be utilized, the encoder performance can be largely improved. The experimental results show that the multi-layer embedded approach can remove most of the noise while achieving spatial scalability. And the R-D curve shows the optional use of inter-layer prediction tools can help yield better denoising performance and coding efficiency.
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    Enming Luo · O.C. Au · Yannan Wu · Shing Fat Tu · Chi-ho Yeung ·
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    ABSTRACT: Scalable Video Coding (SVC) has been approved as the extension of the H.264/AVC video coding standard recently. In current spatial scalability scheme, the technique to examine both inter modes with residual prediction and without residual prediction for enhancement layers can achieve the highest possible coding efficiency, but it's typically one of the most time-consuming parts of a video encoder. In this paper, we propose a method to skip half of motion estimation processes under "inter modes without residual prediction" based on the motion vector predictor selection under "inter modes with residual prediction". Experimental results show that our proposed scheme can achieve up to 24% time saving for motion estimation in the enhancement layer and meanwhile the coding efficiency can be preserved very well.
    Picture Coding Symposium, 2009. PCS 2009; 06/2009
  • Enming Luo · Oscar C. Au · Yannan Wu · Shing Fat Tu ·
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    ABSTRACT: In current spatial scalable video coding (SVC) scheme, some additional tools and more modes are provided in order to improve the coding efficiency for the enhancement layer, but the drawback is that much more coding time is required. In this paper, we propose two schemes from different perspectives to reduce the coding time. In scheme 1, part of the motion estimation (ME) processes are skipped while scheme 2 gives a fast mode decision algorithm for the enhancement layer coding. The experimental results show that for scheme 1, up to 24% time saving can be achieved while for scheme 2, more than 30% time saving can always be achieved and meanwhile the coding efficiency can be preserved well. Moreover, the two proposed schemes can be combined together to further reduce the coding time.
    Advances in Multimedia Information Processing - PCM 2009, 10th Pacific Rim Conference on Multimedia, Bangkok, Thailand, December 15-18, 2009 Proceedings; 01/2009
  • Shing-Fat Tu · Oscar C. Au · Yannan Wu · Enming Luo · Chi-Ho Yeung ·
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    ABSTRACT: This paper proposes a novel framework for frame rate up conversion. The framework contains a motion field estimator employing a hybrid of a novel predictive variable blocksize motion estimation and robust optical flow algorithm. This motion field is more robust and accurate than pure optical flow or pure motion estimation methods. Therefore, in-between frames can be estimated more accurately by the new hybrid method. After the motion field estimation, pixel interpolation following motion field interpolation is done for in-between frames. It is shown the proposed method has better than pure motion estimation and pure optical flow methods in terms of both subjective and objective measurements.
  • Shing Fat Tu · Oscar C. Au · Yannan Wu · Enming Luo · Chi-Ho Yeung ·
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    ABSTRACT: In this paper, a line-warping based deinterlacing method will be introduced. The missing pixels in interlaced videos can be derived from the warping of pixels in horizontal line pairs. In order to increase the accuracy of temporal prediction, multiple temporal-line pairs, selected according to constant velocity model, are used for warping. The stationary pixels can be well-preserved by accuracy stationary detection. A soft switching between spatial-temporal interpolated values and temporal average is introduced in order to prevent unstable switching. Owing to above novelties, the proposed method can yield higher visual quality deinterlaced videos than conventional methods. Moreover, this method can suppress most deinterlaced visual artifacts, such as line-crawling, flickering and ghost-shadow.
    Proceedings of the 2009 IEEE International Conference on Multimedia and Expo, ICME 2009, June 28 - July 2, 2009, New York City, NY, USA; 01/2009
  • Yannan Wu · Oscar C. Au · Enming Luo · Dennis Tu · Leo Yeung ·
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    ABSTRACT: Long has it become a hot topic that reconstructing images of better visual quality from one or a serial of degraded ones. Although there are thousands of different restoration methods, in this paper, we focus on removing the ringing artifact caused by lossy video compression. Being a sort of restoration method, we choose the max-a-posterior (MAP) method to model this optimization problem. Quantification of the ringing artifacts serves as a prior information of the images. So it is also analyzed in this paper. The MAP optimization is further solved using a gradient decent solver. Although this is a quite classical method, there are still lots of problems with it. For settling them, we transform the solver to a filter format operation named iterative optimization filter. Experiments show that, such method could give an averaging 0.3 dB gain and in special regions more than 0.7 dB gain. What is more, as analyzed in this paper, the method is very preferable in terms of hardware implementation in several aspects.
    Proceedings of the 2009 IEEE International Conference on Multimedia and Expo, ICME 2009, June 28 - July 2, 2009, New York City, NY, USA; 01/2009
  • Yannan Wu · Oscar C. Au · Enming Luo · Chi-Ho Yeung · Shing Fat Tu ·
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    ABSTRACT: Image registration based on gradient and least square optimization technique is one of the most edge-cutting registration algorithms. Such method, especially useful for sub-pixel motion, searches for the best motion in an iterative way. This paper solves the same motion registration problem following this direction. And the well-known Gauss-Newton method (GNM) is employed here as the optimization tool. To achieve a speed-up and reduction of the arithmetic calculation, a simplified high order approach(SHoA) used to calculate several parameters for GNM is introduced. Detailed complexity analysis and performance comparison are presented showing that such an approach is a better trade-off between registration error and the number of math operations.
    International Symposium on Circuits and Systems (ISCAS 2009), 24-17 May 2009, Taipei, Taiwan; 01/2009