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)
The recent High Efficiency Video Coding (HEVC) standard was designed to achieve significantly improved compression performance compared to the widely used H.264/AVC standard. This achievement was motivated by the ever-increasing popularity of high-definition video applications and the emergence of ultra-HD. Unfortunately, this comes at the expense of a(More)
The structural similarity (SSIM) index is an objective metric that gives relatively accurate similarity prediction scores with reasonable complexity. In this paper, an excellent trade-off between accuracy and complexity is presented in the form of a wavelet structural similarity index (WSSI), which is more accurate and less complex than the spatial SSIM(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)
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)
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, optimizing for perceived quality (user experience) commands a non-negligible computational cost which in our work,(More)
In this paper, we propose a fast mode decision framework and a fast motion estimation algorithm for H.264 to High Efficiency Video Coding (HEVC) transcoding. The fast mode decision framework employs a post-order (bottom-up) traversal of the coding tree unit (CTU) quadtree. Based on this traversal and H.264 information, several strategies are proposed to(More)
In the context of motion estimation (ME) for video coding, the rate-constrained successive elimination algorithm (RC-SEA) safely eliminates candidate motion vectors while preserving the optimal candidate chosen by the block matching algorithm (BMA). This paper describes a technique for reusing ME information from rectangular to square prediction units in(More)