With many h264/aac videos (whether in mp4/flv/mkv etc container), the audio slowly but progressively gets out of sync, to the point where the video is unwatchable. Seeking to a new position temporarily resets sync and corrects the problem, but audio will just slowly get out of sync again.
In terms of reproducing the problem, unfortunately, it is not consistent across all videos; about 1/3 of my videos seem to manifest this issue. The red flags seem to be h264 w/variable frame rate, and video encoded via Adobe flash (flv videos, even w/constant frame rate, will have the problem).
I am using SMPlayer v16.9 on Linux Mint. This bug only started occuring when I upgraded to 16.9; before that I had never encountered this. It is also not the direct fault of using mpv vs mplayer; if I play back the same video using mpv directly (via command line), the syncing problem does not occur. The problem also does not occur if I play the same videos using other players (Totem, VLC, etc), so the videos themselves are apparently fine. But of course I would much prefer to use SMPlayer, because its interface/usability is so superior.
Anyone else having this problem, or am I just missing something, such as in Preferences settings? Hopefully I'm not alone in this and this is a bug that can be fixed in the next release.