In this thesis, we propose a novel Digital-Down-Converter (DDC) architecture for PC-based software Digital Video Broadcasting-Terrestrial (DVB-T) receiver. We let A/D sampling rate be 192/7 MHz and the order of the lowpass FIR filter be seven (8 coefficients) in DDC. We then propose combining the mixer and filter (CMF), that is, pre-processing the mixer and filter coefficients and storing the results in a look-up table. If the input data of length N, the proposed CMF scheme has 2N multiplications but the previous architecture, which does not pre-process the mixer and filter coefficients together in advance, has 3N multiplications. Finally, we optimize our algorithm in assembly code to satisfy DVB-T real-time reception requirement.