此研究的目的為鑑定H.264/AVC視訊是否曾遭受畫面異常操作，包括畫面片段刪減、插入或抽換等，所提出的方法利用H.264/AVC去區塊濾波器(De-blocking filter)所產生的邊界強度(Boundary Strength, BS)資訊以分析宏區塊(Macroblock)編碼模式。首先，我們以BS資訊產生兩種特徵圖，分別為PRG (Prediction Residual Graph)與IPG (Inter-Prediction Graph)，再依此兩種特徵圖，分別提出VRF (Variation of Residual Footprint)與DOF (Degree of Fragments)兩種特徵，以因應不同的編碼情形與反偵測方法。我們藉由VRF與DOF所產生的數據進行峰值偵測，統計各峰值間的距離後取得此視訊遭受編輯前的原始GOP(Group of Pictures)大小，再分析所產生的峰值圖與原始GOP大小來追蹤峰值的異常週期，並進一步找出待測視訊的畫面操作位置。此外，本論文也針對一個基於改動編碼量化係數及編碼模式，且讓眾多偵測方法失效的新穎反偵測方法進行驗證。實驗結果顯示，不論在二次編碼時採用固定量化係數(Quantization Parameter)或是固定位元率(Constant Bitrate)編碼，在施予若干反偵測與否的情形下都能有穩定且強健的偵測效果。;The purpose of this research is to determine if an investigated H.264/AVC video stream has suffered such manipulations as shot deletion, insertion or replacement. The scheme is designed based on the information of H.264/AVC de-blocking filter, in which the boundary strength (BS) is utilized for analyzing the coding modes of macroblocks. We first employ the BS values to form two feature maps, PRG (Prediction Residual Graph) and IPG (Inter-Prediction Graph). We then further extract two features based on the two feature maps, including VRF (Variation of Residual Footprint) and DOF (Degree of Fragments) to deal with different anti-detection methods or varying coding scenarios. The distances between the detected peaks from VRF and DOF are used to acquire the original GOP (Group of Pictures) size. Finally, with the detected original GOP size and the identified peaks, we can observe the abnormal periodic phenomenon and locate the exact positions of shot manipulation. Several tests and a state-of-the-art anti-detection method that modifies quantized coefficients and coding modes are applied in the experiments to verify the robustness of the proposed scheme.
