Magick String for HDR

Greetings!

I am trying to use Magick++ as an alternative image encoder. We have a
platform dependent one that can encode several buffer formats such as
BGR and YV12 to image formats like PNG and JPEG. All in memory
buffers. I tried to accomplish that with Image Magick and found it
easy to use and capable of the job. I am using Blob and Image from the
Magick++ lib.
The only thing that puzzles me is that "magick" string.
Is that described more precisely than here:
http://www.imagemagick.org/script/formats.php  ??

Specifically HDR formats are of interest.
I understand I would specify a 8bit BGRA buffer with "BGRA" and an
8bit  RGB with simply "RGB".
But how would I, say specify a YV12?
"YV12" doesn't seem to do.
Even more interesting is a 16 bit float HDR BGRA for example.

Can you give me any hint on that?

Cheers,
Stephan