Use the flags argument of av_hwframe_ctx_create_derived() to pass the
mapping flags which will be used on allocation. Also, set the format
and hardware context on the allocated frame automatically - the user
should not be required to do this themselves.
Some frames contexts are not usable without additional format-specific
state in hwctx. This change adds new functions frames_derive_from and
frames_derive_to to initialise this state appropriately when deriving
a frames context which will require it to be set.
Adds functions to convert to/from strings and a function to iterate
over all supported device types. Also adds a new invalid type
AV_HWDEVICE_TYPE_NONE, which acts as a sentinel value.
Adds the new av_hwframe_map() function, which allows mapping between
hardware frames and normal memory, along with internal support for
implementing it.
Also adds av_hwframe_ctx_create_derived(), for creating a hardware
frames context associated with one device using frames mapped from
another by some hardware-specific means.
The source frame may be cropped, so that its dimensions are smaller than
the pool dimensions. The transfer_data API requires the allocated size
of the destination frame to be the same as the pool size.
Mark Thompson
Anton Khirnov
Mark Thompson