Current code returned the number of channels as channel layout in that case,
and if nret is not set then unknown layouts are typically not supported.
Also use the common parsing code. Use a temporary workaround to parse an
unknown channel layout such as '13c', after a 1 year grace period only '13C'
will work.
Signed-off-by: Marton Balint <cus@passwd.hu>
A lot of changes happen at the same time:
- Add a framequeue fifo to AVFilterLink.
- split AVFilterLink.status into status_in and status_out: requires
changes to the few filters and programs that use it directly
(f_interleave, split, filtfmts).
- Add a field ready to AVFilterContext, marking when the filter is ready
and its activation priority.
- Add flags to mark blocked links.
- Change ff_filter_frame() to enqueue the frame.
- Change all filtering functions to update the ready field and the
blocked flags.
- Update ff_filter_graph_run_once() to use the ready field.
- buffersrc: always push the frame immediately.
