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This work presents a low-complexity MP3 algorithm over a fixed-point arithmetic. A new rate control is introduced for the MP3 encoding algorithm, rather than the rate control in ordinary MP3. Taking the loop-independent components outside the loop and accelerating the nonuniform quantizer using a hybrid scheme reduce the computational complexity of the rate control. The hybrid scheme includes a lookup-table method for smaller numbers and a linear piecewise approximation for larger numbers. A precise method for predicting the quantizer parameter is developed to decrease the number of times the rate control is executed. A hybrid scheme is also used in MP3 decoding algorithm to accelerate the dequantization. However, the approximation for larger numbers is two-tier. The first tier is a linear piecewise approximation that yields a rough value. The second tier uses the rough value as the initial value of the first-order Newton's method to obtain a more closely-approximated value. The precise method for prediction has a statistically hit rate of 43%, and the new rate control consumes no more than 4.5 MIPS. The proposed dequantization consumes no more than 2.38 MIPS, and has an error-to-signal ratio of under 0.012%. The implementation of the complexity-reduced MP3 algorithm over 16 bit fixed-point arithmetic is subjectively tested to evaluate the quality of the complexity-reduced MP3 algorithm.