Adaptive divide-and-predict intra-frame coding based on H.264/AVC

Abstract

A new intra-frame coding method is proposed on the basis of H.264/AVC. In the proposed method, every other pixel is sampled either in a horizontal or vertical direction without any anti-aliasing filtering, and two sub-frames of the even-pixel and odd-pixel are then generated. The even-pixel sub-frame is coded as a conventional intra frame while the other is coded as an inter frame which utilizes the intra coded sub-frame. The paper introduces three different inter coding methods- motion compensation-based sub-inter-frame coding, fixed interpolation-based sub-inter-frame coding and adaptive interpolation-based sub-inter-frame coding- for the odd-pixel sub-frame. Our proposed intra coding method can be extended into a multi-level case in which the even-pixel sub-frame is again subdivided into an even-pixel sub-sub-frame and an odd-pixel sub-sub-frame, and further improve the coding performance. Fast coding of the proposed method is also introduced with early mode decision algorithm to reduce the computational complexity. The experimental results show that our proposed schemes outperform the conventional intra-frame coding in H.264/AVC and reduce the bitrate by 11.67% in average at baseline profile while 4.53% at high profile of H.264/AVC. Even in the fast algorithm, 11.56% and 4.31% bitrate savings are achieved at baseline and high profiles respectively with computational complexity reduced to approximately 1/3 which is similar to that of H.264/AVC intra coding.