Development of CRIM system for the automatic speaker verification spoofing and countermeasures challenge 2015

The automatic speaker verification spoofing and countermeasures challenge 2015 provides a common framework for the evaluation of spoofing countermeasures or anti-spoofing techniques in the presence of various seen and unseen spoofing attacks. This contribution proposes a system consisting of amplitude, phase, linear prediction residual, and combined amplitude phase-based countermeasures for the detection of spoofing attacks. In this task we use following features: Mel-frequency cepstral coefficients (MFCC), product spectrum-based cepstral coefficients, modified group delay cepstral coefficients, weighted linear prediction group delay cepstral coefficients, linear prediction residual cepstral coefficients, cosine normalized phase-based cepstral features (CNPCC), and a combination of MFCC-CNPCC. The product spectrum-based features are influenced by both the amplitude and phase spectra. The Gaussian Mixture Model (GMM) classifier is used for the discrimination of the human and spoofed speech signals. Our primary submitted system is a linear fusion of the sub-systems based on the features mentioned above with fusion weights trained on the development dataset. Experimental results on the challenge evaluation data provided an average EER (equal error rate) of 0.041%, 5.347%, and 2.69% on the known, unknown and all (known + unknown) spoofing attacks, respectively. Among all the systems product spectrum-based cepstral coefficientsand conventional MFCC (without any feature normalization)based systems performed the best in terms of EER measure. On the known, unknown and all conditions the EER obtained by the MFCC and product spectrum-based features are 0.78% & 0.65%, 5.39% & 5.37% and 3.09% & 3.01%, respectively.