以動態畫面省略及可靠移動向量提升框速轉換視訊之畫質

Abstract

在視訊壓縮應用中，常因為頻寬的限制必需對於視訊資料在空間或是時間的解析度上有所犧牲。利用降低框速(frame rate)所節省的資料率(bitrate)來維持在空間解析度上的一定畫質，以便於之後利用影像在時間上的關聯性來重建完整的框速；此種節省資料率(bitrate)的方式遠比保留多張畫質不好的畫框(frame)來得有效率。框速轉換(Frame Rate Up-conversion)的應用不僅適用於視訊會議上的壓縮，同時對於慢動作播放特效的需求或是不同播放規格之間的轉換(ex: NTSC vs. PAL)也大有助益。本篇論文為了提昇生成視訊的畫質，提出了一個完整的實作流程，不僅在解碼器(decoder)端去分析視訊影像之內容，同時在編碼器(encoder)端也根據人類視覺系統(Human Vision System)模型動態調整壓縮張數，以大幅增進框速轉換(Frame Rate Up-conversion)後的整體視訊畫質。

Frame rate up-conversion (FRUC) is a post-processing tool to convert the frame rate from a lower number to a higher one. It is a useful technique for a lot of practical applications, such as display format conversion, low bitrate video coding and slow motion playback. Unlike traditional approaches, such as frame repetition or linear frame interpolation, motion-compensated frame interpolation (MCFI) technique which takes block motion into account is regarded as a more efficient scheme. By considering the deficiencies in previous works, new criteria and coding schemes for improving motion derivation and interpolation processes are suggested. In addition, adaptive frame skip is fulfilled at the encoder side to maximize the power of MCFI in video coding applications so that the quality of interpolated frames is guaranteed. Experimental results show that our proposal indeed enhances the overall quality, both subjectively and objectively, of the frame rate up-converted video sequence.