I found that when I use QuickTime Player to play videos, it shows different control panels. Sometimes it shows the normal one like this:
I can click the time and change it to frame. For some reasons, it may display control panels like this:
There is a controller to enable the edit of slow motion. And in this mode, it is impossible to click the time and display frame number. I tested with the same format videos (MP4), and it seems which control panel it displays is kind of random. I was wondering how can I manually enable or disable the "slow motion" bar.