A Study on Error concealment for Image and Video Communications
Date Issued
2004
Date
2004
Author(s)
Lee, Pei-Jun
DOI
zh-TW
Abstract
This dissertation presents some error concealment algorithms for three current developing Image and Video standards that are essential for real-time digital Image/Video transmission systems.
Digital Image/Video transmission is widely used in consumer products, e.g., digital camera, digital TV and hand-held system, etc. The newly defined JPEG 2000 delivers image with lower bit rate in the internet and wireless communications. However, JPEG 2000 decoding is processed bitplane by bitplane. Any data loss in bitstream will affect the consequent bitplanes and even possibly destroy the whole picture. We proposed two new algorithms to recover the damaged bitplanes data. One is according to the correlation information between cross-subbands and undamaged bitplane information. The other method is according to the interested directional sets (IDS) of in-subband. The proposed algorithms are quite simple, but are very efficient in concealing the loss data of any subband in streaming real-time video data in the internet and wireless communications. The simulation results show that the proposed algorithm has 1.5~3dB improvement than previously presented error resilient mechanism. In a subjective view, the proposed concealment algorithm can achieve much smoother edges on the reconstructed images.
In video transmission, two new error concealment algorithms for MPEG-4 object-based video are presented. An algorithm based on fuzzy set theory is proposed to repair damaged portions of the shape information. The feature based error concealment is for MPEG-4 lost shape and texture data. The algorithm consists of a feature matching step to identify temporally corresponding features between video frames and an affine parameter estimation step to find the motion of the feature points. In the feature matching step, an efficient cross-radial search (CRS) method is developed to find the best matching points. In the affine parameter estimation step, a non-iterative least squares estimation algorithm is developed to estimate the affine parameters. An attractive feature of the algorithm is that the shape data and texture data are handled by the same method. Unlike previous methods, this unified approach works for the case where the video object undergoes a drastic movement, such as a sharp turn. Experimental results show that the proposed algorithm performs much better than previous approaches by about 0.3~2.8 dB for shape data and 1.6~5.0 dB for texture data.
In H.264/AVC low bit rate data transmission, a new error concealment algorithm for the new coding standard H.264 is presented. The algorithm consists of a block size determination step to determine the size type of the lost block and a motion vector recovery step to find the lost motion vector from multiple reference frames. The main features of this algorithm are as follows. In the block size determination step, we propose a criterion to determine the size type of the lost block from the current frame. In the motion vector recovery step, the optimal motion vector for the lost block chosen from multiple previous reference frames with the minimum value of the side match distortion. The proposed algorithm not only can determine the most correct mode for the lost block, but also can save much more computation time for motion vector recovery. Experimental results show that the proposed algorithm achieves 0.4~7 dB improvement than conventional VM method does.
These techniques can greatly improve the image/video quality and be suitable implemented for image/video transmission systems. The proposed algorithms are applied in decoder when error is detected in bitstream domain for image coding by JPEG 2000, and are applied in image domain for video coding by MPEG-4 or H.264/AVC.
Subjects
視訊壓縮
錯誤修補
視訊傳輸
video communication
error concealment
JPEG 2000
video coding
MPEG-4
H.264/AVC
Type
thesis