how to copy multi-dim Array into IntPtr (or byte[])?

[Kirk Marple]

an external API that we're using is giving me back video data in a
multi-dimensional Array (not byte[], just System.Array). so, for an HD
quality video, the data is organized as [3][1280][720] of bytes. i know
this rather weird, but it's what i have to work with...

i've been reading thru Array.Copy and other related methods, but nothing
seems appropriate or efficient.

i'd rather not have to copy into a big byte[] array and them Marshal.Copy
that into an allocated IntPtr, but if that's what it takes, i'll have to do
it.

my biggest problem is i don't even know how to flatten the multi-dim array
into a byte[] array. optimally, i'd like to do it into one step into the
allocated IntPtr from the multi-dim array.

thanks for any help,
Kirk