Stéphane Coulombe

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This paper describes a novel multi-frame and multi-slice parallel video encoding approach with simultaneous encoding of predicted frames. The approach, when applied to H.264 encoding, leads to speedups comparable to those obtained by state-of-the-art approaches, but without the disadvantage of requiring bidirectional frames. The new approach uses a number(More)
A common transcoding operation consists of reducing the file size of a JPEG image to meet bandwidth or device constraints. This can be achieved by reducing its quality factor (QF) or reducing its resolution, or both. In this paper, using the structural similarity (SSIM) index as the quality metric, we present a system capable of estimating the QF and(More)
This work presents two new algorithms to predict the file size of a JPEG image subject to transformations consisting of simultaneous changes in resolution (scaling) and in quality factor (QF). To be computationally efficient, the prediction is based solely on easily accessible image parameters such as the quality factor and the original file size. A large(More)
Reducing the file size of a JPEG image to meet bandwidth or terminal constraints is a common transcoding operation. The reduction can be achieved by reducing either the quality factor (QF) or the resolution, or both. In this paper, we analyze the impact of QF and scaling parameter choices on the quality of the resulting images, as measured by a quality(More)
—Error concealment has long been identified as the last line of defense against transmission errors. Since error handling is outside the scope of video coding standards, decoders may choose to simply ignore corrupted packets or attempt to decode their content. In this paper, we present a novel joint source-channel decoding approach that can be applied to(More)
Département de génie logiciel et des technologies de l'information École de technologie supérieure Abstract The problem of efficiently adapting JPEG images to satisfy given constraints such as maximum file size and resolution arises in a number of applications, from universal media access for mobile browsing to multimedia messaging services. However,(More)
Today, professional documents, created in applications such as PowerPoint and Word, can be shared using ubiquitous mobile terminals connected to the Internet. GoogleDocs and EasyMeet are good examples of such collaborative web applications dedicated to professional documents. The static adaptation of professional documents has been studied extensively.(More)
Multimedia Messaging Services (MMS) allow messages composed of different media attachments to be exchanged between heterogeneous devices. In this work, we consider the special case of image-only messages, where the challenge is to adapt messages so that the receiving device constraints are satisfied while maximizing the user's perceived quality of adapted(More)
c 1997 IEEE. Personal use of this material is permitted. However , permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. ABSTRACT This paper(More)