This field may be set by the caller before calling av_hwdevice_ctx_init().
If non-NULL, this callback will be called when the last reference to
this context is unreferenced, immediately before it is freed.
@note when other objects (e.g an AVHWFramesContext) are derived from this
struct, this callback will be invoked after all such child objects
are fully uninitialized and their respective destructors invoked.
This field may be set by the caller before calling av_hwdevice_ctx_init().
If non-NULL, this callback will be called when the last reference to this context is unreferenced, immediately before it is freed.
@note when other objects (e.g an AVHWFramesContext) are derived from this struct, this callback will be invoked after all such child objects are fully uninitialized and their respective destructors invoked.