Patent ID: 8223849

Claim:
A picture decoder, coupled to a host controller for encoding/decoding video data based on a H.264 standard, the picture decoder comprising: a decoded picture buffer (DPB) controller, for accessing reference pictures and a decoded picture when a picture is decoded and displayed; a picture storage, having a plurality of reference picture storage spaces and a reconstructed picture space, wherein the reference picture storage spaces have a sequence state; a reference state register (RSR), coupled to the DPB controller, for storing a usage state of the reference picture storage spaces, wherein the unused reference picture storage spaces among the reference picture storage spaces are released; a reconstruct address register (RAR), coupled to the DPB controller; and a decoder, coupled to the host controller, the RSR, the RAR, and the picture storage, wherein after the host controller decodes a header information of an input picture, the host controller determines whether the input picture is used for reference subsequently and starts the DPB controller, and the DPB controller determines a reconstruct address of a picture to be decoded and stores the reconstruct address into the RAR, wherein after the DPB controller stores the reconstruct address into the RAR, the host controller starts the decoder to execute a video decoding, and after the decoder completes the video decoding, the decoder fills a reconstruct information into the reconstructed picture space according to the reconstruct address and updates the usage state of the RSR, wherein the decoder updates the RSR about the reference pictures being currently referred and the DPB also simulates the RSR as a simulated RSR state, wherein after the host controller notifies the DPB controller to start controlling function, the DPB controller compares the simulated RSR state with the RSR to find out the difference in the bits, which indicating the reference pictures being currently removed, wherein the DPB controller updates the simulated RSR state with the RSR and updates the usage state of the reference picture storage spaces in the RAR to release the reference picture storage spaces for the reference pictures being currently removed, wherein after the decoder completes the video decoding, the host controller continues to decode a next picture.