Artículos

Spatial Error Concealment Based on Bezier Curves

Ocultamiento de Errores Espacial Mediante Curvas de Bezier

Rogelio Hasimoto–Beltrán¹ and Ashfaq A. Khokhar²

1 Centro de Investigación en Matemáticas – CIMAT
Jalisco s/n, Col. Mineral de Valenciana, Guanajuato, Gto., México 36240
Tel: +52–(473)–732–7155 ext. 49636, Fax: +52–(473)–732–5749
hasimoto@cimat.mx

2 University of Illinois at Chicago,
Departments of Computer Sciences and Electrical and Computer Engineering,
851 South Morgan Street, Chicago, IL 60607, USA
ashfaq@uic.edu

Article received on December 16, 2003; accepted on December 12, 2005

Abstract

We present a geometric error concealment scheme for Discrete Cosine Transform (DCT) based image/video data based on the Bezier Curves (BC). Our scheme unlike the original proposal of Zeng and Liu, 1999, makes use of the average edge direction and local curvature (extracted from healthy blocks around the damaged block) as boundary conditions to create an n–degree BC. The BC is then used to interpolate the edge of the lost block (8x8 pixels), as well as to directionally reconstruct its low frequency data. In those cases where more than one edge is found to cross the lost area, a cost function defined in terms of the local and global edge curvature is used to find their best match. Results show that our approach provides an almost perfect reconstruction and excellent subjective quality of the restored data, outperforming current linear interpolations schemes in the literature.

Keywords: Error Concealment, DCT–based compression, Bezier Curves.

Resumen

Se presenta un esquema nuevo para el ocultamiento de errores de transmisión (pérdidas de paquetes) en imágenes y video basado en las Curvas de Bezier (BC). El esquema propuesto a diferencia de la propuesta original de Zeng y Liu, 1999, hace uso de la dirección promedio de los bordes y curvatura local alrededor de la zona dañada como condiciones de frontera para crear una curva de Bezier de grado n. La BC es usada para interpolar los bordes del bloque perdido (8x8 pixels), así como también para la reconstrucción de la información correspondiente a las bajas frecuencias. En casos donde más de un borde atraviesa la zona dañada, se propone una función de costo en términos de sus curvaturas local y global para encontrar sus correspondientes pares y proceder con el proceso de interpolación (reconstrucción) de la información perdida. Los resultados muestran que nuestro esquema reconstruye casi perfectamente la información perdida (durante la transmisión) lo que repercute en una excelente calidad subjetiva de la imagen/video reconstruido. Nuestro esquema es muy superior a los interpoladores lineales encontrados en la literatura.

Palabras Clave: Ocultamiento de Errores, Compresión basada en la DCT, Curvas de Bezier.

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Acknowledgement

This work was supported by CONCYTEG (Consejo Estatal de Ciencia y Tecnología de Guanjuato) under grant number 04–02–K117–020.

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