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| A New Method for Estimating the Primary Quantization Step of JPEG Double-Compression |
| Wang Jun-wen①; Liu Guang-jie①; Dai Yue-wei①; Zhou Lin-na②; Guo Yun-biao② |
| ①School of Automation, Nanjing University of Science & Technology, Nanjing 210094, China; ②Beijing Application Institute of Electronic Technology, Beijing 100091, China |
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Abstract This paper presents a method for estimating the primary quantization step of double compressed JPEG image. The method in accordance with the relationship between the two quantization steps contains three situations. When the primary quantization step is larger than the second quantization step, the histogram can be used to calculate directly. To resolve the issue of multi-value caused by Fourier spectrum analysis and the problem that the primary quantization step is the factor of the second quantization step, the uncompressed image can be approximated by narrowing the image by 98%. This method can resolve the problem that the primary quantization step is the factor of the second quantization step, and uses spectrum analysis to reduce the complexity. The experimental results show that this method has higher accuracy of the estimation.
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Received: 25 December 2007
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2009, Vol. 31 
