本研究探討AV1視訊編碼資料隱藏，改良基於調整幀內編碼之預測角 度嵌入方法，並分析係數嵌入方法的影響。既有的AV1Stego方法主要於 位元流輸出階段修改預測角度資訊，證明於AV1中進行隱寫術的可行 性。然而，該嵌入結果不再回到前端預測與殘差計算流程，於是在高嵌入 量條件下常造成畫質劣化。本研究將資料嵌入時機調整至率失真最佳化完 成後、最終模式資訊寫入前的階段，降低資料於候選模式更新過程中被覆 蓋的可能，同時也減少對額外控制參數的依賴。 StegAV1 於全幀內（Intra-only）與關鍵幀（Key frame）畫面的方向性 預測區塊進行資料嵌入，以奇偶對映方式調整角度偏移值，解碼端依據角 度偏移值平移後的奇偶性還原隱藏位元。StegAV1在不同位元率條件下皆 能穩定完成資料嵌入與擷取，且在中高位元率編碼下維持良好的客觀畫 質，在嵌入穩定性與視覺品質維持間取得良好平衡。此外，於AV1中以 係數修改的方法嵌入資訊，資訊隱藏量與畫質表現會受到若干編碼條件所 影響，本研究建議依據不同情況調整嵌入條件，降低資料擷取不同步的風 險與畫質損耗，可作為後續更高容量AV1視訊資料隱藏設計的參考。;This study investigates data hiding in AV1 video coding by improving a prediction-angle-based embedding method that modifies intra-frame coding and analyzes the effects of coefficient-based embedding. Existing AV1Stego primarily modified prediction-angle information at the bitstream output stage， demonstrating the feasibility of steganography in AV1. However， the embedded information of AV1Stego is not fed back into the preceding prediction and residual calculation processes so high embedding payloads can result in noticeable visual degradation. In this study， the embedding process is moved to the stage after rate-distortion optimization and before the final mode information is written， thereby reducing the possibility that the embedded data will be overwritten during candidate-mode updates while minimizing the reliance on additional control parameters. StegAV1 embeds data into directional prediction blocks in both intra-only and key frames. The hidden bits are embedded by adjusting the parity of angular offsets， while the decoder recovers the hidden bits according to the parity of the angular offset after the corresponding shift. Experimental results show that StegAV1 can reliably embed and extract data under different bitrate conditions. It also maintains good objective visual quality at medium-to-high bitrates， achieving a favorable balance between embedding reliability and visual quality preservation. In addition， when coefficient modification is adopted for data embedding in AV1， both the embedding capacity and visual quality are affected by several coding conditions. We therefore recommend adjusting the embedding conditions according to different coding scenarios to reduce the risk of ii synchronization failures during data extraction and minimize visual quality degradation. These findings can serve as a reference for the development of higher-capacity data hiding schemes for AV1 video.
