I have the same async issues with mpv and it even gets worse, when I increase the playback speed to 1.2. Then the SVP Index alternates between 1.2 and 1.4.
But going back to the DirectShow/ffdshow based players (MPC-HC, Potplayer) I get a straight 1.00 line as my SVP Index. With higher speeds on these players the index goes up to 1.2 but the graph stays at this value and does not go up and down a little.
My system has a Xeon E3-1231 v3 CPU and a GTX 1070. Is this too slow for SVP?´
edit:
On the left I use Potplayer/ffdshow on normal playback speed and then on 1.2x speed. On the right the same with mpv. The mpv playback gets out of sync in less than a minute.
The video was just a current 720p release from HorribeSubs.