This adds a new API, which allows the API user to query the required
AVHWFramesContext parameters. This also reduces code duplication across
the hwaccels by introducing ff_decode_get_hw_frames_ctx(), which uses
the new API function. It takes care of initializing the hw_frames_ctx
if needed, and does additional error handling and API usage checking.
Support for VDA and Cuvid missing.
Signed-off-by: Anton Khirnov <anton@khirnov.net>
Moves much of the setup logic for VAAPI decoding into lavc; the user
now need only provide the hw_frames_ctx.
(cherry picked from commit 123ccd07c5)
(cherry picked from commit 5e879b54a3)
(cherry picked from commit 0aec37e625)
(cherry picked from commit cfa4eb4fba)