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 filename/f, original_size, fontsdir, and alpha from the subtitles filter, plus the following option:

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. Required for correct rendering of complex scripts such as Arabic, Hebrew, Devanagari and Thai. Requires libass to be built with HarfBuzz.

The default is auto.