IBM - CVUT Student Research Projects Speech recognition frontend on Cell BE Pavel Bazika (bazikp1@fel.cvut.cz)
Speech recognizer • Input speech is represented by samples • Inner format is 25ms length frames FRONTEND speech comparison vocabulary •preprocessing •feature extraction word probability IBM - CVUT Student Research Projects 2
Algorithms needed for speech recognition • Mean value subtraction • Preemphasis • Hamming window selection } cepstrum • FFT • Logarithm • Triangular filters • DCT IBM - CVUT Student Research Projects 3
Speed of our algorithm • Four frames are computed at once • Cepstrum calculation of 25 ms length frame for input sampling frequency 8 kHz takes 3,7 μs • One SPU can process 2700 speeches in realtime IBM - CVUT Student Research Projects 4
Cepstrum calculation comparison with Pentium 4 30000 25000 20000 Time [ns] SPU F4S 15000 Pentium 4 10000 5000 0 0 200 400 600 800 1000 1200 Frame size IBM - CVUT Student Research Projects 5
Highlights • Optimized algorithms for SPU, dual-issue used when possible • FFT for four streams of data implemented • Pentium 4 is slower in every algorithm • Faster FFT than FFTW with SSE2 enabled • Input samples are converted to inner format in parallel with mean value computation IBM - CVUT Student Research Projects 6
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