特点：
    实时、高分辨率，
    GPU帧率fps：4k[3840x2160]-30fps，HD[1920x1080]-60fps

    （额外背景帧bgr，src）->( alpha matte，fgr）

    困难点：

    • high quality alpha matte + strand-level hair details
    • high resolution images in real time

    网络结构

    • Base：low-resolution result（？）+ error prediction map
    • Refine：refined at high resolution on selectivte patches

    数据

    • PhotoMatte 13K/85
    • VideoMatte240K

    Segmentation
    coarse boundaries at high resolution

    • ASPP from DeepLabv3
    • DeepLabv3+