osxaudio review todo

gistfile1.txt

audiounitinitialize on open - test on OS X and iOS
get_caps - okay
cached_caps_valid - take lock in property notification only if on outer element
                    can we just use cached_caps == NULL for marking invalid?
with/without channel-mask in caps - keep both, since we want to expose what the
                                    device has, and also allow remapping
                                  - if !channel_mask, we're adding duplicate
                                    structures
                                  - out_s1 should be before out_s2
G_STRUCT_OFFSET - maybe just add a single line note like: 
                  "This works because mChannelDescriptions is a variable length array"
warning on mismatched channel count - check behaviour, if remapping, upmix,
                                      downmix is intelligent, drop warning