We present a novel optical arbitrary waveform generation approach based on pair-by-pair pulse shaping. Based on the heterodyne between a pair of optical frequency combs with different repetition rates, the repetition rate of the generated signals can be flexibly tuned from MHz to GHz without changing the setup. The restriction of the spectral resolution of the optical spectrum processor is overcome by the pair-by-pair approach while the spectral resolution of the system can be improved to MHz by dual-comb heterodyne. Hyperfine control of a higher resolution spectrum at MHz is achieved, which benefits the generation of the ultrawideband signals.