This patch is analogous to 20f972701806be20a77f808db332d9489343bb78:
It hides the internal part of AVFilter by adding a new internal
structure FFFilter (declared in filters.h) that has an AVFilter
as its first member; the internal part of AVFilter is moved to
this new structure.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
It differs from query_func() in accepting arrays of input/output format
configurations to be filled as callback parameters. This allows to mark
the filter context as const, ensuring it is not modified by this
function, as it is not supposed to have any side effects beyond
returning the supported formats.
Specifically those that should be visible to filters, but hidden from
API callers. Such properties are currently located at the end of the
public AVFilterLink struct, demarcated by a comment marking them as
private. However it is generally better to hide them explicitly, using
the same pattern already employed in avformat or avcodec.
The new struct is currently trivial, but will become more useful in
following commits.
Unlike av_frame_is_writable(), it uses the link's alloc callback,
making direct rendering possible.
The code comes from ff_filter_frame_framed(), moved with mostly
trivial changes.
