Biomedical subjects

Luis Ducla Soares

Publications and source records attributed to Luis Ducla Soares.

3 recordsLinked to original sources

PubMed2006

Temporal shape error concealment by global motion compensation with local refinement.

This paper presents an original temporal shape error concealment technique based on a combination of global and local motion compensation. For this technique, which is especially useful for object-based video applications in error-prone environments (e.g., mobile networks), it is assumed that the shape of the corrupted object at hand is in the form of a binary alpha plane and some of the shape data is missing due to channel errors. To conceal the corrupted shape, the decoder first assumes that a global motion model can describe the shape changes in consecutive time instants. This way, based on locally estimated global motion parameters, the decoder attempts to conceal the corrupted alpha plane by global motion compensating the shape data from the previous time instant. Afterwards, since a global motion model cannot perfectly describe all alpha plane changes, a local motion refinement is applied to improve the concealment in areas of the object with significant local motion.

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PubMed2004

Spatial shape error concealment for object-based image and video coding.

In this paper, an original spatial shape error-concealment technique, to be used in the context of object-based image and video coding schemes, is proposed. In this technique, it is assumed that the shape of the corrupted object at hand is in the form of a binary alpha plane, in which some of the shape data is missing due to channel errors. From this alpha plane, a contour corresponding to the border of the object can be extracted. However, due to errors, some parts of the contour will be missing and, therefore, the contour will be broken. The proposed technique relies on the interpolation of the missing contours with Bézier curves, which is done based on the available surrounding contours. After all the missing parts of the contour have been interpolated, the concealed alpha plane can be easily reconstructed from the fully recovered contour and used instead of the erroneous one improving the final subjective impact.

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PubMed2004

Adaptive shape and texture intra refreshment schemes for improved error resilience in object-based video coding.

Video encoders may use several techniques to improve error resilience. In particular, for video encoders that rely on predictive (inter) coding to remove temporal redundancy, intra coding refreshment is especially useful to stop temporal error propagation when errors occur in the transmission or storage of the coded streams, since these errors may cause the decoded quality to decay very rapidly. In the context of object-based video coding, intra coding refreshment can be applied to both the shape and texture data. In this paper, novel shape and texture intra refreshment schemes are proposed which can be used by object-based video encoders, such as MPEG-4 video encoders, independently or combined. These schemes allow to adaptively determine when the shape and texture of the various video objects in a scene should be refreshed in order to maximize the decoded video quality for a certain total bit rate.

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