12019 If the rendering target is left undefined, it will be inherited from the default style.
12021 Disallow subtitle animation. Enabling this option will lower CPU usage. You can use it if you experience flashing subtitles.
12022 Increasing the number of buffered subpictures should in general improve the rendering performance at the cost of a higher video RAM usage on the GPU.
14202 If the rendering target is left undefined, SSA/ASS subtitles will be rendered relative to the video frame while all other text subtitles will be rendered relative to the window.
22081 If "latest keyframe" is selected, seek to the first keyframe before the actual seek point.\nIf "nearest keyframe" is selected, seek to the first keyframe before or after the seek point depending on which is the closest.