While I choose mpv as the back-end of smplayer, the hardware acceleration of video (vdpau) can't be used in the video and falls down to the software decoding.
Meanwhile, if I choose mplayer as the back-end of smplayer, the same video can be decoded via vdpau.
Moreover, if I use cli to play the same video via mpv, the video can also be decoded via vdpau.
So, how to make mpv work well with hardware acceleration when it is used as a back-end of Smplayer?