Intended for use with hardware frames for which rawvideo is not
sufficient. Requires the trusted packet flag to be set - decoding
fails if not to avoid security issues (the wrapped AVFrame can
contain pointers to arbitrary data).
This ensures that the wrapped avframe will not get reallocated later, which
would invalidate internal references such as extended data.
Reviewed-by: wm4 <nfxjfg@googlemail.com>
Signed-off-by: Marton Balint <cus@passwd.hu>
