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Publication details
Authors T.BianchiA.Piva
Title Detection of Nonaligned Double JPEG Compression Based on Integer Periodicity Maps
Abstract In this paper, a simple yet reliable algorithm to detect the presence of nonaligned double JPEG compression (NA-JPEG) in compressed images is proposed. The method evaluates a single feature based on the integer periodicity of the blockwise dicrete cosine transform coefficients when the DCT is computed according to the grid of the previous JPEG compression. Even if the proposed feature is computed relying only on DC coefficient statistics, a simple threshold detector can classify NA-JPEG images with improved accuracy with respect to existing methods and on smaller image sizes, without resorting to a properly trained classifier. Moreover, the proposed scheme is able to accurately estimate the grid shift and the quantization step of the DC coefficient of the primary JPEG compression, allowing to perform a more detailed analysis of possibly forged images. Source code available: demo-NA-JPEG.rar.
Publication IEEE Transactions on Information Forensics & Security
Typology International Journal Papers
Date April 2012 (published online Oct. 2011)
Other info vol. 7, no. 2, pp. 842-848, 
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