Should be set instead of @ref AVFilter.init "init" by the filters that
want to pass a dictionary of AVOptions to nested contexts that are
allocated during init.
On return, the options dict should be freed and replaced with one that
contains all the options which could not be processed by this filter (or
with NULL if all the options were processed).
Otherwise the semantics is the same as for @ref AVFilter.init "init".
Should be set instead of @ref AVFilter.init "init" by the filters that want to pass a dictionary of AVOptions to nested contexts that are allocated during init.
On return, the options dict should be freed and replaced with one that contains all the options which could not be processed by this filter (or with NULL if all the options were processed).
Otherwise the semantics is the same as for @ref AVFilter.init "init".