YUV420 format

YUV420

YUV420:

    YUV420P:
        I420: YYYYYYYY UU VV
        YV12: YYYYYYYY VV UU

    YUV420SP:
        NV12: YYYYYYYY UVUV
        NV21: YYYYYYYY VUVU

reference:
yuv422，yuv420，yuv444的区别 https://blog.csdn.net/rjszcb/article/details/118728264
YUV图像格式通俗详解（大量图） https://mp.weixin.qq.com/s/MUp0BLhpVVdY0r4h8vn0Tg