vaapidecodebin: add postprocessor dynamically
The former approach to left the bin unfinished has some problems: the context
cannot be shared because the vaapidecode is unlinked in many cases, leading to
creating a VADisplay twice.
Initially the bin is fully functional, constructed as
(-----------------------------------)
| vaapidecodebin |
| (-------------) (-------) |
|<--| vaapidecode |--->| queue |--->|
| (-------------) (-------) |
(-----------------------------------)
When the context is shared and the VADisplay has VPP capabilities, before
changing to READY state, the bin is reconfigured dynamically, adding the
vaapipostproc element afeter the queue:
(--------------------------------------------------------)
| vaapidecodebin |
| (-------------) (-------) (---------------) |
|<--| vaapidecode |--->| queue |--->| vaapipostproc |--->|
| (-------------) (-------) (---------------) |
(--------------------------------------------------------)
Signed-off-by: Víctor Manuel Jáquez Leal <victorx.jaquez@intel.com>
https://bugzilla.gnome.org/show_bug.cgi?id=757957