Department of Information and Communications Engineering, Sejong University, Seoul, South Korea.
IEEE Trans Image Process. 2011 Aug;20(8):2177-88. doi: 10.1109/TIP.2011.2155075. Epub 2011 May 16.
We propose an adaptive loop filter to remove the redundancy between current and motion compensated frames so that the residual signal is minimized, thus coding efficiency increases. The loop filter coefficients and offset are optimized for each frame or a set of blocks to minimize the total energy of the residual signal resulting from motion estimation and compensation. The optimized loop filter with offset is applied for the set of blocks where the filtering process gives coding gain based upon rate-distortion cost. The proposed loop filter is used for the motion compensated frame whereas the conventional adaptive interpolation filter (AIF) is applied to the reference frames to interpolate the subpixel values. Another conventional scheme adaptive loop filter (ALF), is used after deblocking filtering to enhance quality of reconstructed frames, not to minimize energy of residual signal. The proposed loop filter can be used in combination with the AIF and ALF. Experimental results show that proposed algorithm provides the averaged bit reduction of 8% compared to conventional H.264/AVC scheme. When the proposed scheme is combined with AIF and ALF, the coding gain increases even further.
我们提出了一种自适应环路滤波器，用于去除当前帧和运动补偿帧之间的冗余，从而使残差信号最小化，从而提高编码效率。环路滤波器系数和偏移量针对每一帧或一组块进行优化，以最小化运动估计和补偿产生的残差信号的总能量。具有偏移的优化环路滤波器应用于一组块中，该组块的滤波过程根据率失真代价提供编码增益。所提出的环路滤波器用于运动补偿帧，而传统的自适应插值滤波器（AIF）应用于参考帧以插值子像素值。另一种传统的自适应环路滤波器（ALF）方案用于去块滤波之后，以增强重建帧的质量，而不是最小化残差信号的能量。所提出的环路滤波器可以与 AIF 和 ALF 结合使用。实验结果表明，与传统的 H.264/AVC 方案相比，所提出的算法平均减少了 8%的比特数。当所提出的方案与 AIF 和 ALF 结合使用时，编码增益甚至进一步提高。
