At the top:

%define         gst_minver      0.8.7
%define         gstp_minver     0.8.5
%define         gstreamer       gstreamer


Yet later it refers to:

Requires:       %{gstreamer} >= %{_gst_minver}
Requires:       %{gstreamer}-plugins >= %{_gstp_minver}

BuildRequires:  %{gstreamer}-devel >= %{_gst_minver}
BuildRequires:  %{gstreamer}-plugins-devel >= %{_gstp_minver}

Either the defines need the leading '_', or the Requires/BuildRequires need it
removed...