The transmission of block-coded visual information over packet networks introduces fidelity problems in terms of data losses, which result in wrong reconstruction of block sequences at the decoder. Concealment techniq...
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The transmission of block-coded visual information over packet networks introduces fidelity problems in terms of data losses, which result in wrong reconstruction of block sequences at the decoder. Concealment techniques aim at masking the visual effect of these errors, by exploiting either spatial or temporal available information. Both temporal and spatial approaches present drawbacks: the first is in general inefficient in handling complex or fast objects' motion, while the second is computationally expensive and is not able to recover high-frequency contents and small details. In this paper, a new solution is proposed that combines temporal and spatial approaches. The technique first replaces the lost block with the best matching pattern in a previously decoded frame (BMA), using the border information, and then applies a mesh-based warping (MBW) that reduces the artifacts caused by fast movements, rotations or deformations. The first step is achieved by a fast matchingalgorithm, for a high precision is not needed, while the second step uses an affine transform applied to a deformable mesh structure. Experimental results show that significant improvements can be achieved in comparison with traditional spatial or temporal concealment approaches, in terms of both subjective and objective reconstruction quality.
Compressed video sequences are very vulnerable to channel disturbances when they are transmitted through the burst-packet-loss networks such as a wireless channel. An effective solution for packet loss is to perform c...
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Compressed video sequences are very vulnerable to channel disturbances when they are transmitted through the burst-packet-loss networks such as a wireless channel. An effective solution for packet loss is to perform concealment at the receiver. Most of the spatial and/or temporal concealment methods estimate the true motion vector (W) associated with a missing block by using the MVs of adjacent blocks. However, these methods can not conceal effectively the missing blocks, since the neighboring blocks can be easily lost by the burst packet losses destroying a large area of coded video. In this paper, we present a robust error concealment method of estimating the true MV of the missing block by using the bidirectional motion tracking technique within neighboring frames of a damaged frame. This motion tracking technique uses the linear trajectory feature of the image block in the forward and backward prediction directions. Experimental results show that the proposed algorithm has superior subjective and objective video quality than conventional error concealment Methods in the burst-packet-loss environments.
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