What color format should use to encode i420 frame converted by libyuv in mediacodec?

Question

I converted nv21 frame to i420 frame with libyuv, and then encode the frame into a video file with mediacodec, the video looks strange. I use COLOR_FormatYUV420SemiPlanar and COLOR_FormatYUV420Flexible color format.

So, what color format should i use to encode i420 frame converted by libyuv.