The option that works for me is
pix_fmt=p010le
It produces the following info
Video
ID : 1
Format : HEVC
Format/Info : High Efficiency Video Coding
Format profile : Main 10@L4@Main
Codec ID : V_MPEGH/ISO/HEVC
...
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 10 bits
No color banding now. I’m so happy. ^^