This callback may be set by the caller immediately after allocating the
graph and before adding any filters to it, to provide a custom
multithreading implementation.
If set, filters with slice threading capability will call this callback
to execute multiple jobs in parallel.
If this field is left unset, libavfilter will use its internal
implementation, which may or may not be multithreaded depending on the
platform and build options.
This callback may be set by the caller immediately after allocating the graph and before adding any filters to it, to provide a custom multithreading implementation.
If set, filters with slice threading capability will call this callback to execute multiple jobs in parallel.
If this field is left unset, libavfilter will use its internal implementation, which may or may not be multithreaded depending on the platform and build options.