关键词: 双压缩, MP3语音, 改进的离散余弦变换（MDCT）系数, 拟合

Abstract: MP3 speech tampering process usually includes three operations, i.e., decompression, tampering, recompression, which will inevitably introduce a double compression. Therefore, double compression detection is a necessary condition for MP3 speech tampering detection. In this work, the statistical characteristics of quantized MDCT coefficients are analyzed, and a model is established for fitting the relationship between speech duration and those characteristics. Finally, a method is put forward, which can not only effectively detect double compression for MP3 speech, but also reveal the relationship between speech duration and detection accuracy.

Key words: double compression, MP3 speech, Modified Discrete Cosine Transform（MDCT） coefficients, fitting