Called only once right before the filter is freed. Should deallocate any
memory held by the filter, release any buffer references, etc. It does
not need to deallocate the AVFilterContext.priv memory itself.
This callback may be called even if @ref AVFilter.init "init" was not
called or failed, so it must be prepared to handle such a situation.
Filter uninitialization function.
Called only once right before the filter is freed. Should deallocate any memory held by the filter, release any buffer references, etc. It does not need to deallocate the AVFilterContext.priv memory itself.
This callback may be called even if @ref AVFilter.init "init" was not called or failed, so it must be prepared to handle such a situation.