Stéphane Coulombe

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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)
— 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)
In mobile video applications, where unreliable networks are commonplace , corrupted video packets can have a profound impact on the quality of the user experience. In this paper, we show that, in a wide range of operating conditions, selectively reusing data resulting from decodable errorneous packets leads to better results than frame copy. This selection(More)
The problem of adapting JPEG images to satisfy constraints such as file size and resolution arises in a number of applications, from universal media access to mul-timedia messaging services. Visually optimized adaptation, however, commands a non-negligible computational cost which we aim to minimize using predictors. In previous works, we presented(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)
The Multimedia Messaging Service (MMS) platform allows messages composed of various multimedia attachments to be exchanged between users of mobile devices. However, these heterogeneous devices exhibit different capabilities regarding what media types, resolution , and maximal message size they support making the adaptation of messages mandatory to ensure(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)