Purpose: Fill out the default/unset parameters with ones actually in use.

Note: Matches the current MediaSDK example code.  This code used to be
present in ffmpeg and was eliminated in revision 1f26a231 on Oct. 31,
2016 (qsv: Merge libav implementation, at
https://github.com/FFmpeg/FFmpeg/commit/1f26a231bb065276cd80ce02957c759f3197edfa#diff-7d84a34d58597bb7aa4b8239dca1f9f8).
Already applied to libav.
Reviewed-by: Luca Barbato <lu_zero@gentoo.org>
(cherry picked from commit b22094d7)
Signed-off-by: Mark Thompson <sw@jkqxz.net>
Signed-off-by: Aaron Levinson <alevinsn@aracnet.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>