结合率失真代价预测的HEVC快速CU划分

针对高效率视频编码(high efficiency video coding,HEVC)标准编码复杂度较高的问题,提出了一种快速编码单元(coding unit,CU)划分方法。首先,结合拉格朗日率失真优化理论及相关实验数据分析得到相邻CU深度对应的失真及码率分别满足线性关系,并利用此关系,建立了率失真代价的预测模型。利用此模型,可以在编码当前CU深度后快速预测得到下一CU深度的率失真代价,并最终通过代价比较,判断是否需要继续进行CU划分。实验结果表明,相比于HEVC测试模型HM12.0,针对低时延与随机接入编码结构,提出的方法的BD-rate分别增加了0.2%与0.6%,同时,编码时间分别减少了33.2%和38.9%。

基于感知的AVS2帧内编码的编码单元尺寸快速决策算法研究

AVS2是由中国数字音视频编解码技术标准工作组独立提出的一种视频编码标准。帧内编码是AVS2的关键技术之一。在帧内编码中,AVS2引入了基于四叉树的编码单元(Coding Unit,CU)划分方法,使得编码性能显著提高,但是计算复杂度急剧增加。为了有效地降低帧内编码的计算复杂度,研究人员已经研究了许多CU尺寸快速决策算法。然而,传统的CU尺寸快速决策算法主要的关注点在于保持视频的客观性能几乎不变的条件下,减少编码的时间,而没有对视频的主观性能进行考虑。这就意味着可以对基于感知的CU尺寸快速决策算法进行进一步的研究。本文提出了一种基于时空相邻信息和内部感知纹理信息的编码单元尺寸快速决策算法。实验结果表明,在RD17.0的全帧内测试配置下,该方法平均可减少28.06%的时间复杂度,主观性能损失可忽略不计。

基于感知的帧内快速模式决策算法研究

AVS2是由中国数字音视频编解码技术标准工作组独立提出的一种视频编码标准。帧内编码是AVS2的关键技术之一。在帧内编码中,AVS2采取了33种帧内预测模式,使得编码性能显著提高,但是计算复杂度急剧增加。为了有效地降低帧内编码的计算复杂度,研究人员已经研究了许多帧内模式快速决策算法。然而,传统的帧内模式快速决策算法主要的关注点在于保持视频的客观性能几乎不变的条件下,减少编码的时间,而没有对视频的主观性能进行考虑。这就意味着可以对基于感知的帧内模式快速决策算法进行进一步的研究。本文提出了一种基于感知的帧内快速模式决策算法。实验结果表明,在RD17.0的全帧内测试配置下,该方法平均可减少16.93%的时间,基于SSIM的BD-Rate损失为1.07%。

Ultrafast epitaxial growth of metre-sized single-crystal graphene on industrial Cu foil

A foundation of the modern technology that uses single-crystal silicon has been the growth of highquality single-crystal Si ingots with diameters up to 12 inches or larger. For many applications of graphene, large-area high-quality(ideally of single-crystal) material will be enabling. Since the first growth on copper foil a decade ago, inch-sized single-crystal graphene has been achieved. We present here the growth, in 20 min, of a graphene film of(5 ×50) cm^2 dimension with >99% ultra-highly oriented grains.This growth was achieved by:(1) synthesis of metre-sized single-crystal Cu(1 1 1) foil as substrate;(2)epitaxial growth of graphene islands on the Cu(1 1 1) surface;(3) seamless merging of such graphene islands into a graphene film with high single crystallinity and(4) the ultrafast growth of graphene film.These achievements were realized by a temperature-gradient-driven annealing technique to produce single-crystal Cu(1 1 1) from industrial polycrystalline Cu foil and the marvellous effects of a continuous oxygen supply from an adjacent oxide. The as-synthesized graphene film, with very few misoriented grains(if any), has a mobility up to ~23,000 cm^2 V^(-1)s^(-1)at 4 K and room temperature sheet resistance of ~230 Ω/□. It is very likely that this approach can be scaled up to achieve exceptionally large and high-quality graphene films with single crystallinity, and thus realize various industrial-level applications at a low cost.