1. vcm mode is only available for H264.
2. vcm is not supported on Linux, but it is shown when run "./avconv -h
encoder=h264_qsv |grep vcm". This shouldn't happen.
Signed-off-by: Zhong Li <zhong.li@intel.com>
Signed-off-by: Maxym Dmytrychenko <maxim.d33@gmail.com>