| 摘要 |
An IMDCT co-processor and an audio decoder having the same are provided to reduce an MIPS(Million Instruction Per Second) value, and a decoding time of a digital processor for audio decoding by reducing the whole operation amount of a digital signal processor for the audio decoding, thereby realizing an MPEG-4(Moving Picture Experts Group-4) audio decoder suitable for real time mobile multimedia environment. An IMDCT(Inverse Modified Discrete Cosine Transform) co-processor comprises the followings: an input buffer(410); an I/Q(In-phase/Quadrature-phase) separator(420); the first operation unit(430) for performing complex-multiplication operation on data, divided by the I/Q separator(420), and a specific twiddle factor; an IFFT(Inverse Fast Fourier Transform) unit(440) which performs inverse fast fourier transform on the operation result value from the first operation unit(430) and outputs the result value; the second operation unit(450) for performing complex-multiplication operation on the result value, outputted from the IFFT unit(440), and a specific twiddle factor; a deinterleaver(460) which receives the operation result value from the second operation unit(450) to arrange the data and inverse-maps a positive value(+) and a negative value(-) of a certain portion to each other to output a final IMDCT time sample value; and a control register(470) which selects an inputted inverse-quantized frequency spectrum sample value according to a specific window sequence value to determine the final IMDCT time sample value.
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