Abstract: A fast Fourier transform (FFT) circuit of an audio processing device configured to perform an N-points FFT and including a memory circuit and a butterfly operation unit circuit is provided. The butterfly operation unit circuit reads two points input data from the memory circuit, performs a butterfly operation for the two points input data according to a twiddle factor to generate two points output data, and writes the two points output data into the memory circuit. The butterfly operation unit circuit includes a multiplier and a plurality of adders/subtractors. The multiplier sequentially multiplies real or imaginary coefficients of one of the two points input data by real or imaginary coefficients of the twiddle factor in multiple clock cycles. The multiplier performs a multiplication once in each clock cycle. The adders/subtractors perform addition/subtraction, such that the butterfly operation unit circuit generates the two points output data.

Abstract: An audio processing device for speech recognition is provided, which includes a memory circuit, a power spectrum transfer circuit, and a feature extraction circuit. The power spectrum transfer circuit is coupled to the memory circuit, reads frequency spectrum coefficients of time-domain audio sample data from the memory circuit, generates compressed power parameters by performing a power spectrum transfer processing and a compressing processing according to the frequency spectrum coefficients, and writes the compressed power parameters into the memory circuit. The feature extraction circuit is coupled to the memory circuit, reads the compressed power parameters from the memory circuit, generates an audio feature vector by performing mel-filtering and frequency-to-time transfer processing according to the compressed power parameters. The bit width of the compressed power parameters is less than the bit width of the frequency spectrum coefficients.

Abstract: A fast Fourier transform (FFT) circuit of an audio processing device configured to perform an N-points FFT and including a memory circuit and a butterfly operation unit circuit is provided. The butterfly operation unit circuit reads two points input data from the memory circuit, performs a butterfly operation for the two points input data according to a twiddle factor to generate two points output data, and writes the two points output data into the memory circuit. The butterfly operation unit circuit includes a multiplier and a plurality of adders/subtracters. The multiplier sequentially multiplies real or imaginary coefficients of one of the two points input data by real or imaginary coefficients of the twiddle factor in multiple clock cycles. The multiplier performs a multiplication once in each clock cycle. The adders/subtractors perform addition/subtraction, such that the butterfly operation unit circuit generates the two points output data.

Abstract: An audio processing device for speech recognition is provided, which includes a memory circuit, a power spectrum transfer circuit, and a feature extraction circuit. The power spectrum transfer circuit is coupled to the memory circuit, reads frequency spectrum coefficients of time-domain audio sample data from the memory circuit, generates compressed power parameters by performing a power spectrum transfer processing and a compressing processing according to the frequency spectrum coefficients, and writes the compressed power parameters into the memory circuit. The feature extraction circuit is coupled to the memory circuit, reads the compressed power parameters from the memory circuit, generates an audio feature vector by performing mel-filtering and frequency-to-time transfer processing according to the compressed power parameters. The bit width of the compressed power parameters is less than the bit width of the frequency spectrum coefficients.