A reference picture information communication interface implemented in a hardware/software integrated H.264 encoder/decoder is provided. The reference picture information communication interface includes a reference state register (RSR) and a reconstruct address register (RAR). The RSR has N bits, wherein N represents the maximum number of reference pictures supported by the H.264 encoder/decoder. The RSR is used by the hardware for notifying a software decoded picture buffer (DPB) controller about a current reference picture existence information. The RAR is used by the software for notifying the H.264 encoder/decoder about an address of a reconstruction information of a currently decoded picture in a memory space.