ass

Same as the subtitles filter, except that it doesn't require libavcodec and libavformat to work. On the other hand, it is limited to ASS (Advanced Substation Alpha) subtitles files.

This filter accepts the following option in addition to the common options from the subtitles filter:

'shaping'

Set the shaping engine

Available values are:

'auto'

The default libass shaping engine, which is the best available.

'simple'

Fast, font-agnostic shaper that can do only substitutions

'complex'

Slower shaper using OpenType for substitutions and positioning

The default is auto.