This paper addresses the problem of transcoding compressed video bitstreams to reduced spatio-temporal resolutions. We propose a new technique to compensate drift error based on the principle of intra-block refresh. We also investigate other important issues related to the transcoding, such as the re-estimation of motion vectors and DCT coefficients. The rate control related to intra-refresh is...

Applications like distance learning and teleconferencing often require compression of images that contain both text and graphics. Because text and graphics have different properties, a compression scheme can benefit by treating the textual and graphical portions of such compound images separately. In this paper, we propose new methods, called Transform Coefficient Likelihood (TCL) schemes, for ...

In many JPEG image splicing forgeries, the tampered image patch has been JPEG-compressed twice with different block alignments. Such phenomenon in JPEG image forgeries is called the shifted double JPEG (SDJPEG) compression effect. Detection of SDJPEG-compressed patches could help in detecting and locating the tampered region. However, the current SDJPEG detection methods do not provide satisfac...

The FPL implementation of an 8×8 Two Dimensional Discrete Cosine Transform (2D-DCT) processor based on the Residue Number System (RNS) is presented in this paper. It makes use of a Fast Cosine Transform (FCT) algorithm that requires a single multiplication stage for each signal path, while most other algorithms include paths with more than one multiplication. The row-column decomposition techni...

We examine the impact of various encoding parameters on the distribution of the DCT coefficients for H.264-like video coders. We model the distribution of the frame DCT coefficients using the most common Laplacian and Cauchy distributions. We show that the resolution, the quantization levels and the coding type have significant impact on the accuracy of the Laplacian and Cauchy distribution bas...

—Recently, a fast radix-algorithm for an efficient computation of the type-IV discrete cosine transform (DCT-IV) has been proposed in [1], where is an odd positive integer. In particular, based on the proposed fast algorithm, optimized efficient 3-, 5-, and 9-point scaled DCT-IV (SDCT-IV) modules have been derived in [1]. As a response, an improved efficient optimized 9-point scaled DCT-IV (SDC...