H.264/AVC是目前已發展完成並且壓縮率最高的視訊編碼標準，它支援Intra16×16、Intra4×4的亮度(Luminance)預測及Intra8×8的彩度(Chrominance) 預測做畫面內預測編碼。H.264/AVC利用相鄰的畫素間的相關性，以減少I Frame的冗餘資料，以達到壓縮目的。 對於所有的候選預測模式(candidate mode)，逐一Rate-Distortion Optimization(RDO)運算會增加龐大計算量。為了要降低畫面內預測編碼的運算複雜度，本論文提出一階小波轉換畫面快速偵測演算法(Fast Intra Prediction with Haar Transform Algorithm)主要是針對Intra4×4紋理較為複雜，而Intra16x16紋理較為平坦的特性，利用一階小波轉換後所得的低頻資訊先行區分Macroblock，並針對Intra16x16與Intra4x4先行判斷垂直偵測與水平偵測，藉由減少RDO的候選模式，已達成H.264整體壓縮時間降低的目的。實驗結果顯示，本論文所提出的演算法，可以有效地降低運算複雜度而讓整體壓縮時間降低，且能維持與H.264 Full Search相似的預測結果。 H.264/AVC is well-known for its performance on coding efficiency. It has advantages of low bit-rate and high image quality. However, the complexity of H.264/AVC encoder limits applications in the real time video communication. In this study, a fast intra prediction with Haar transform algorithm (FIPHTA) is proposed to simplify the complexity of luma intra prediction. For each luma macroblock (MB), a Haar transform is first executed. By observing LL coefficients, this MB will be classified as I16-MB, I4-MB, or both. An I16-MB indicates that this MB is smooth and only Intra 16×16 (I16) prediction modes are to be considered. An I4-MB indicates that this MB is textured and only Intra 4×4 (I4) prediction modes are to be considered. And the rest of MBs (both) have to consider both prediction modes as in the standard H.264/AVC. Next, to choose an I16 prediction mode for a MB, the vertical and horizontal energies of the LL coefficients are calculated to reduce candidate modes. Similarly, the pixel-based vertical and horizontal energies are calculated for a 4x4 block to reduce I4 candidate modes. The simulation showed that the proposed algorithm can maintain the similar mode selection results comparing to the full search algorithm of H.264 but with a remarkable computation deduction.
